// SPDX-License-Identifier: GPL-2.0
/*
 * This driver enables Trace Buffer Extension (TRBE) as a per-cpu coresight
 * sink device could then pair with an appropriate per-cpu coresight source
 * device (ETE) thus generating required trace data. Trace can be enabled
 * via the perf framework.
 *
 * The AUX buffer handling is inspired from Arm SPE PMU driver.
 *
 * Copyright (C) 2020 ARM Ltd.
 *
 * Author: Anshuman Khandual <anshuman.khandual@arm.com>
 */
#define DRVNAME "arm_trbe"

#define pr_fmt(fmt) DRVNAME ": " fmt

#include <asm/barrier.h>
#include <asm/cpufeature.h>

#include "coresight-self-hosted-trace.h"
#include "coresight-trbe.h"

#define PERF_IDX2OFF(idx, buf) ((idx) % ((buf)->nr_pages << PAGE_SHIFT))

/*
 * A padding packet that will help the user space tools
 * in skipping relevant sections in the captured trace
 * data which could not be decoded. TRBE doesn't support
 * formatting the trace data, unlike the legacy CoreSight
 * sinks and thus we use ETE trace packets to pad the
 * sections of the buffer.
 */
#define ETE_IGNORE_PACKET               0x70

/*
 * Minimum amount of meaningful trace will contain:
 * A-Sync, Trace Info, Trace On, Address, Atom.
 * This is about 44bytes of ETE trace. To be on
 * the safer side, we assume 64bytes is the minimum
 * space required for a meaningful session, before
 * we hit a "WRAP" event.
 */
#define TRBE_TRACE_MIN_BUF_SIZE         64

enum trbe_fault_action {
        TRBE_FAULT_ACT_WRAP,
        TRBE_FAULT_ACT_SPURIOUS,
        TRBE_FAULT_ACT_FATAL,
};

struct trbe_buf {
        /*
         * Even though trbe_base represents vmap()
         * mapped allocated buffer's start address,
         * it's being as unsigned long for various
         * arithmetic and comparision operations &
         * also to be consistent with trbe_write &
         * trbe_limit sibling pointers.
         */
        unsigned long trbe_base;
        /* The base programmed into the TRBE */
        unsigned long trbe_hw_base;
        unsigned long trbe_limit;
        unsigned long trbe_write;
        int nr_pages;
        void **pages;
        bool snapshot;
        struct trbe_cpudata *cpudata;
};

/*
 * TRBE erratum list
 *
 * The errata are defined in arm64 generic cpu_errata framework.
 * Since the errata work arounds could be applied individually
 * to the affected CPUs inside the TRBE driver, we need to know if
 * a given CPU is affected by the erratum. Unlike the other erratum
 * work arounds, TRBE driver needs to check multiple times during
 * a trace session. Thus we need a quicker access to per-CPU
 * errata and not issue costly this_cpu_has_cap() everytime.
 * We keep a set of the affected errata in trbe_cpudata, per TRBE.
 *
 * We rely on the corresponding cpucaps to be defined for a given
 * TRBE erratum. We map the given cpucap into a TRBE internal number
 * to make the tracking of the errata lean.
 *
 * This helps in :
 *   - Not duplicating the detection logic
 *   - Streamlined detection of erratum across the system
 */
#define TRBE_WORKAROUND_OVERWRITE_FILL_MODE     0
#define TRBE_WORKAROUND_WRITE_OUT_OF_RANGE      1

static int trbe_errata_cpucaps[] = {
        [TRBE_WORKAROUND_OVERWRITE_FILL_MODE] = ARM64_WORKAROUND_TRBE_OVERWRITE_FILL_MODE,
        [TRBE_WORKAROUND_WRITE_OUT_OF_RANGE] = ARM64_WORKAROUND_TRBE_WRITE_OUT_OF_RANGE,
        -1,             /* Sentinel, must be the last entry */
};

/* The total number of listed errata in trbe_errata_cpucaps */
#define TRBE_ERRATA_MAX                 (ARRAY_SIZE(trbe_errata_cpucaps) - 1)

/*
 * Safe limit for the number of bytes that may be overwritten
 * when ARM64_WORKAROUND_TRBE_OVERWRITE_FILL_MODE is triggered.
 */
#define TRBE_WORKAROUND_OVERWRITE_FILL_MODE_SKIP_BYTES  256

/*
 * struct trbe_cpudata: TRBE instance specific data
 * @trbe_flag           - TRBE dirty/access flag support
 * @trbe_hw_align       - Actual TRBE alignment required for TRBPTR_EL1.
 * @trbe_align          - Software alignment used for the TRBPTR_EL1.
 * @cpu                 - CPU this TRBE belongs to.
 * @mode                - Mode of current operation. (perf/disabled)
 * @drvdata             - TRBE specific drvdata
 * @errata              - Bit map for the errata on this TRBE.
 */
struct trbe_cpudata {
        bool trbe_flag;
        u64 trbe_hw_align;
        u64 trbe_align;
        int cpu;
        enum cs_mode mode;
        struct trbe_buf *buf;
        struct trbe_drvdata *drvdata;
        DECLARE_BITMAP(errata, TRBE_ERRATA_MAX);
};

struct trbe_drvdata {
        struct trbe_cpudata __percpu *cpudata;
        struct perf_output_handle * __percpu *handle;
        struct hlist_node hotplug_node;
        int irq;
        cpumask_t supported_cpus;
        enum cpuhp_state trbe_online;
        struct platform_device *pdev;
};

static void trbe_check_errata(struct trbe_cpudata *cpudata)
{
        int i;

        for (i = 0; i < TRBE_ERRATA_MAX; i++) {
                int cap = trbe_errata_cpucaps[i];

                if (WARN_ON_ONCE(cap < 0))
                        return;
                if (this_cpu_has_cap(cap))
                        set_bit(i, cpudata->errata);
        }
}

static inline bool trbe_has_erratum(struct trbe_cpudata *cpudata, int i)
{
        return (i < TRBE_ERRATA_MAX) && test_bit(i, cpudata->errata);
}

static inline bool trbe_may_overwrite_in_fill_mode(struct trbe_cpudata *cpudata)
{
        return trbe_has_erratum(cpudata, TRBE_WORKAROUND_OVERWRITE_FILL_MODE);
}

static inline bool trbe_may_write_out_of_range(struct trbe_cpudata *cpudata)
{
        return trbe_has_erratum(cpudata, TRBE_WORKAROUND_WRITE_OUT_OF_RANGE);
}

static int trbe_alloc_node(struct perf_event *event)
{
        if (event->cpu == -1)
                return NUMA_NO_NODE;
        return cpu_to_node(event->cpu);
}

static void trbe_drain_buffer(void)
{
        tsb_csync();
        dsb(nsh);
}

static void trbe_drain_and_disable_local(void)
{
        u64 trblimitr = read_sysreg_s(SYS_TRBLIMITR_EL1);

        trbe_drain_buffer();

        /*
         * Disable the TRBE without clearing LIMITPTR which
         * might be required for fetching the buffer limits.
         */
        trblimitr &= ~TRBLIMITR_ENABLE;
        write_sysreg_s(trblimitr, SYS_TRBLIMITR_EL1);
        isb();
}

static void trbe_reset_local(void)
{
        trbe_drain_and_disable_local();
        write_sysreg_s(0, SYS_TRBLIMITR_EL1);
        write_sysreg_s(0, SYS_TRBPTR_EL1);
        write_sysreg_s(0, SYS_TRBBASER_EL1);
        write_sysreg_s(0, SYS_TRBSR_EL1);
}

static void trbe_report_wrap_event(struct perf_output_handle *handle)
{
        /*
         * Mark the buffer to indicate that there was a WRAP event by
         * setting the COLLISION flag. This indicates to the user that
         * the TRBE trace collection was stopped without stopping the
         * ETE and thus there might be some amount of trace that was
         * lost between the time the WRAP was detected and the IRQ
         * was consumed by the CPU.
         *
         * Setting the TRUNCATED flag would move the event to STOPPED
         * state unnecessarily, even when there is space left in the
         * ring buffer. Using the COLLISION flag doesn't have this side
         * effect. We only set TRUNCATED flag when there is no space
         * left in the ring buffer.
         */
        perf_aux_output_flag(handle, PERF_AUX_FLAG_COLLISION);
}

static void trbe_stop_and_truncate_event(struct perf_output_handle *handle)
{
        struct trbe_buf *buf = etm_perf_sink_config(handle);

        /*
         * We cannot proceed with the buffer collection and we
         * do not have any data for the current session. The
         * etm_perf driver expects to close out the aux_buffer
         * at event_stop(). So disable the TRBE here and leave
         * the update_buffer() to return a 0 size.
         */
        trbe_drain_and_disable_local();
        perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED);
        perf_aux_output_end(handle, 0);
        *this_cpu_ptr(buf->cpudata->drvdata->handle) = NULL;
}

/*
 * TRBE Buffer Management
 *
 * The TRBE buffer spans from the base pointer till the limit pointer. When enabled,
 * it starts writing trace data from the write pointer onward till the limit pointer.
 * When the write pointer reaches the address just before the limit pointer, it gets
 * wrapped around again to the base pointer. This is called a TRBE wrap event, which
 * generates a maintenance interrupt when operated in WRAP or FILL mode. This driver
 * uses FILL mode, where the TRBE stops the trace collection at wrap event. The IRQ
 * handler updates the AUX buffer and re-enables the TRBE with updated WRITE and
 * LIMIT pointers.
 *
 *      Wrap around with an IRQ
 *      ------ < ------ < ------- < ----- < -----
 *      |                                       |
 *      ------ > ------ > ------- > ----- > -----
 *
 *      +---------------+-----------------------+
 *      |               |                       |
 *      +---------------+-----------------------+
 *      Base Pointer    Write Pointer           Limit Pointer
 *
 * The base and limit pointers always needs to be PAGE_SIZE aligned. But the write
 * pointer can be aligned to the implementation defined TRBE trace buffer alignment
 * as captured in trbe_cpudata->trbe_align.
 *
 *
 *              head            tail            wakeup
 *      +---------------------------------------+----- ~ ~ ------
 *      |$$$$$$$|################|$$$$$$$$$$$$$$|               |
 *      +---------------------------------------+----- ~ ~ ------
 *      Base Pointer    Write Pointer           Limit Pointer
 *
 * The perf_output_handle indices (head, tail, wakeup) are monotonically increasing
 * values which tracks all the driver writes and user reads from the perf auxiliary
 * buffer. Generally [head..tail] is the area where the driver can write into unless
 * the wakeup is behind the tail. Enabled TRBE buffer span needs to be adjusted and
 * configured depending on the perf_output_handle indices, so that the driver does
 * not override into areas in the perf auxiliary buffer which is being or yet to be
 * consumed from the user space. The enabled TRBE buffer area is a moving subset of
 * the allocated perf auxiliary buffer.
 */

static void __trbe_pad_buf(struct trbe_buf *buf, u64 offset, int len)
{
        memset((void *)buf->trbe_base + offset, ETE_IGNORE_PACKET, len);
}

static void trbe_pad_buf(struct perf_output_handle *handle, int len)
{
        struct trbe_buf *buf = etm_perf_sink_config(handle);
        u64 head = PERF_IDX2OFF(handle->head, buf);

        __trbe_pad_buf(buf, head, len);
        if (!buf->snapshot)
                perf_aux_output_skip(handle, len);
}

static unsigned long trbe_snapshot_offset(struct perf_output_handle *handle)
{
        struct trbe_buf *buf = etm_perf_sink_config(handle);

        /*
         * The ETE trace has alignment synchronization packets allowing
         * the decoder to reset in case of an overflow or corruption.
         * So we can use the entire buffer for the snapshot mode.
         */
        return buf->nr_pages * PAGE_SIZE;
}

static u64 trbe_min_trace_buf_size(struct perf_output_handle *handle)
{
        u64 size = TRBE_TRACE_MIN_BUF_SIZE;
        struct trbe_buf *buf = etm_perf_sink_config(handle);
        struct trbe_cpudata *cpudata = buf->cpudata;

        /*
         * When the TRBE is affected by an erratum that could make it
         * write to the next "virtually addressed" page beyond the LIMIT.
         * We need to make sure there is always a PAGE after the LIMIT,
         * within the buffer. Thus we ensure there is at least an extra
         * page than normal. With this we could then adjust the LIMIT
         * pointer down by a PAGE later.
         */
        if (trbe_may_write_out_of_range(cpudata))
                size += PAGE_SIZE;
        return size;
}

/*
 * TRBE Limit Calculation
 *
 * The following markers are used to illustrate various TRBE buffer situations.
 *
 * $$$$ - Data area, unconsumed captured trace data, not to be overridden
 * #### - Free area, enabled, trace will be written
 * %%%% - Free area, disabled, trace will not be written
 * ==== - Free area, padded with ETE_IGNORE_PACKET, trace will be skipped
 */
static unsigned long __trbe_normal_offset(struct perf_output_handle *handle)
{
        struct trbe_buf *buf = etm_perf_sink_config(handle);
        struct trbe_cpudata *cpudata = buf->cpudata;
        const u64 bufsize = buf->nr_pages * PAGE_SIZE;
        u64 limit = bufsize;
        u64 head, tail, wakeup;

        head = PERF_IDX2OFF(handle->head, buf);

        /*
         *              head
         *      ------->|
         *      |
         *      head    TRBE align      tail
         * +----|-------|---------------|-------+
         * |$$$$|=======|###############|$$$$$$$|
         * +----|-------|---------------|-------+
         * trbe_base                            trbe_base + nr_pages
         *
         * Perf aux buffer output head position can be misaligned depending on
         * various factors including user space reads. In case misaligned, head
         * needs to be aligned before TRBE can be configured. Pad the alignment
         * gap with ETE_IGNORE_PACKET bytes that will be ignored by user tools
         * and skip this section thus advancing the head.
         */
        if (!IS_ALIGNED(head, cpudata->trbe_align)) {
                unsigned long delta = roundup(head, cpudata->trbe_align) - head;

                delta = min(delta, handle->size);
                trbe_pad_buf(handle, delta);
                head = PERF_IDX2OFF(handle->head, buf);
        }

        /*
         *      head = tail (size = 0)
         * +----|-------------------------------+
         * |$$$$|$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$ |
         * +----|-------------------------------+
         * trbe_base                            trbe_base + nr_pages
         *
         * Perf aux buffer does not have any space for the driver to write into.
         */
        if (!handle->size)
                return 0;

        /* Compute the tail and wakeup indices now that we've aligned head */
        tail = PERF_IDX2OFF(handle->head + handle->size, buf);
        wakeup = PERF_IDX2OFF(handle->wakeup, buf);

        /*
         * Lets calculate the buffer area which TRBE could write into. There
         * are three possible scenarios here. Limit needs to be aligned with
         * PAGE_SIZE per the TRBE requirement. Always avoid clobbering the
         * unconsumed data.
         *
         * 1) head < tail
         *
         *      head                    tail
         * +----|-----------------------|-------+
         * |$$$$|#######################|$$$$$$$|
         * +----|-----------------------|-------+
         * trbe_base                    limit   trbe_base + nr_pages
         *
         * TRBE could write into [head..tail] area. Unless the tail is right at
         * the end of the buffer, neither an wrap around nor an IRQ is expected
         * while being enabled.
         *
         * 2) head == tail
         *
         *      head = tail (size > 0)
         * +----|-------------------------------+
         * |%%%%|###############################|
         * +----|-------------------------------+
         * trbe_base                            limit = trbe_base + nr_pages
         *
         * TRBE should just write into [head..base + nr_pages] area even though
         * the entire buffer is empty. Reason being, when the trace reaches the
         * end of the buffer, it will just wrap around with an IRQ giving an
         * opportunity to reconfigure the buffer.
         *
         * 3) tail < head
         *
         *      tail                    head
         * +----|-----------------------|-------+
         * |%%%%|$$$$$$$$$$$$$$$$$$$$$$$|#######|
         * +----|-----------------------|-------+
         * trbe_base                            limit = trbe_base + nr_pages
         *
         * TRBE should just write into [head..base + nr_pages] area even though
         * the [trbe_base..tail] is also empty. Reason being, when the trace
         * reaches the end of the buffer, it will just wrap around with an IRQ
         * giving an opportunity to reconfigure the buffer.
         */
        if (head < tail)
                limit = round_down(tail, PAGE_SIZE);

        /*
         * Wakeup may be arbitrarily far into the future. If it's not in the
         * current generation, either we'll wrap before hitting it, or it's
         * in the past and has been handled already.
         *
         * If there's a wakeup before we wrap, arrange to be woken up by the
         * page boundary following it. Keep the tail boundary if that's lower.
         *
         *      head            wakeup  tail
         * +----|---------------|-------|-------+
         * |$$$$|###############|%%%%%%%|$$$$$$$|
         * +----|---------------|-------|-------+
         * trbe_base            limit           trbe_base + nr_pages
         */
        if (handle->wakeup < (handle->head + handle->size) && head <= wakeup)
                limit = min(limit, round_up(wakeup, PAGE_SIZE));

        /*
         * There are two situation when this can happen i.e limit is before
         * the head and hence TRBE cannot be configured.
         *
         * 1) head < tail (aligned down with PAGE_SIZE) and also they are both
         * within the same PAGE size range.
         *
         *                      PAGE_SIZE
         *              |----------------------|
         *
         *              limit   head    tail
         * +------------|------|--------|-------+
         * |$$$$$$$$$$$$$$$$$$$|========|$$$$$$$|
         * +------------|------|--------|-------+
         * trbe_base                            trbe_base + nr_pages
         *
         * 2) head < wakeup (aligned up with PAGE_SIZE) < tail and also both
         * head and wakeup are within same PAGE size range.
         *
         *              PAGE_SIZE
         *      |----------------------|
         *
         *      limit   head    wakeup  tail
         * +----|------|-------|--------|-------+
         * |$$$$$$$$$$$|=======|========|$$$$$$$|
         * +----|------|-------|--------|-------+
         * trbe_base                            trbe_base + nr_pages
         */
        if (limit > head)
                return limit;

        trbe_pad_buf(handle, handle->size);
        return 0;
}

static unsigned long trbe_normal_offset(struct perf_output_handle *handle)
{
        struct trbe_buf *buf = etm_perf_sink_config(handle);
        u64 limit = __trbe_normal_offset(handle);
        u64 head = PERF_IDX2OFF(handle->head, buf);

        /*
         * If the head is too close to the limit and we don't
         * have space for a meaningful run, we rather pad it
         * and start fresh.
         *
         * We might have to do this more than once to make sure
         * we have enough required space.
         */
        while (limit && ((limit - head) < trbe_min_trace_buf_size(handle))) {
                trbe_pad_buf(handle, limit - head);
                limit = __trbe_normal_offset(handle);
                head = PERF_IDX2OFF(handle->head, buf);
        }
        return limit;
}

static unsigned long compute_trbe_buffer_limit(struct perf_output_handle *handle)
{
        struct trbe_buf *buf = etm_perf_sink_config(handle);
        unsigned long offset;

        if (buf->snapshot)
                offset = trbe_snapshot_offset(handle);
        else
                offset = trbe_normal_offset(handle);
        return buf->trbe_base + offset;
}

static void clr_trbe_status(void)
{
        u64 trbsr = read_sysreg_s(SYS_TRBSR_EL1);

        WARN_ON(is_trbe_enabled());
        trbsr &= ~TRBSR_IRQ;
        trbsr &= ~TRBSR_TRG;
        trbsr &= ~TRBSR_WRAP;
        trbsr &= ~(TRBSR_EC_MASK << TRBSR_EC_SHIFT);
        trbsr &= ~(TRBSR_BSC_MASK << TRBSR_BSC_SHIFT);
        trbsr &= ~TRBSR_STOP;
        write_sysreg_s(trbsr, SYS_TRBSR_EL1);
}

static void set_trbe_limit_pointer_enabled(unsigned long addr)
{
        u64 trblimitr = read_sysreg_s(SYS_TRBLIMITR_EL1);

        WARN_ON(!IS_ALIGNED(addr, (1UL << TRBLIMITR_LIMIT_SHIFT)));
        WARN_ON(!IS_ALIGNED(addr, PAGE_SIZE));

        trblimitr &= ~TRBLIMITR_NVM;
        trblimitr &= ~(TRBLIMITR_FILL_MODE_MASK << TRBLIMITR_FILL_MODE_SHIFT);
        trblimitr &= ~(TRBLIMITR_TRIG_MODE_MASK << TRBLIMITR_TRIG_MODE_SHIFT);
        trblimitr &= ~(TRBLIMITR_LIMIT_MASK << TRBLIMITR_LIMIT_SHIFT);

        /*
         * Fill trace buffer mode is used here while configuring the
         * TRBE for trace capture. In this particular mode, the trace
         * collection is stopped and a maintenance interrupt is raised
         * when the current write pointer wraps. This pause in trace
         * collection gives the software an opportunity to capture the
         * trace data in the interrupt handler, before reconfiguring
         * the TRBE.
         */
        trblimitr |= (TRBE_FILL_MODE_FILL & TRBLIMITR_FILL_MODE_MASK) << TRBLIMITR_FILL_MODE_SHIFT;

        /*
         * Trigger mode is not used here while configuring the TRBE for
         * the trace capture. Hence just keep this in the ignore mode.
         */
        trblimitr |= (TRBE_TRIG_MODE_IGNORE & TRBLIMITR_TRIG_MODE_MASK) <<
                      TRBLIMITR_TRIG_MODE_SHIFT;
        trblimitr |= (addr & PAGE_MASK);

        trblimitr |= TRBLIMITR_ENABLE;
        write_sysreg_s(trblimitr, SYS_TRBLIMITR_EL1);

        /* Synchronize the TRBE enable event */
        isb();
}

static void trbe_enable_hw(struct trbe_buf *buf)
{
        WARN_ON(buf->trbe_hw_base < buf->trbe_base);
        WARN_ON(buf->trbe_write < buf->trbe_hw_base);
        WARN_ON(buf->trbe_write >= buf->trbe_limit);
        set_trbe_disabled();
        isb();
        clr_trbe_status();
        set_trbe_base_pointer(buf->trbe_hw_base);
        set_trbe_write_pointer(buf->trbe_write);

        /*
         * Synchronize all the register updates
         * till now before enabling the TRBE.
         */
        isb();
        set_trbe_limit_pointer_enabled(buf->trbe_limit);
}

static enum trbe_fault_action trbe_get_fault_act(struct perf_output_handle *handle,
                                                 u64 trbsr)
{
        int ec = get_trbe_ec(trbsr);
        int bsc = get_trbe_bsc(trbsr);
        struct trbe_buf *buf = etm_perf_sink_config(handle);
        struct trbe_cpudata *cpudata = buf->cpudata;

        WARN_ON(is_trbe_running(trbsr));
        if (is_trbe_trg(trbsr) || is_trbe_abort(trbsr))
                return TRBE_FAULT_ACT_FATAL;

        if ((ec == TRBE_EC_STAGE1_ABORT) || (ec == TRBE_EC_STAGE2_ABORT))
                return TRBE_FAULT_ACT_FATAL;

        /*
         * If the trbe is affected by TRBE_WORKAROUND_OVERWRITE_FILL_MODE,
         * it might write data after a WRAP event in the fill mode.
         * Thus the check TRBPTR == TRBBASER will not be honored.
         */
        if ((is_trbe_wrap(trbsr) && (ec == TRBE_EC_OTHERS) && (bsc == TRBE_BSC_FILLED)) &&
            (trbe_may_overwrite_in_fill_mode(cpudata) ||
             get_trbe_write_pointer() == get_trbe_base_pointer()))
                return TRBE_FAULT_ACT_WRAP;

        return TRBE_FAULT_ACT_SPURIOUS;
}

static unsigned long trbe_get_trace_size(struct perf_output_handle *handle,
                                         struct trbe_buf *buf, bool wrap)
{
        u64 write;
        u64 start_off, end_off;
        u64 size;
        u64 overwrite_skip = TRBE_WORKAROUND_OVERWRITE_FILL_MODE_SKIP_BYTES;

        /*
         * If the TRBE has wrapped around the write pointer has
         * wrapped and should be treated as limit.
         *
         * When the TRBE is affected by TRBE_WORKAROUND_WRITE_OUT_OF_RANGE,
         * it may write upto 64bytes beyond the "LIMIT". The driver already
         * keeps a valid page next to the LIMIT and we could potentially
         * consume the trace data that may have been collected there. But we
         * cannot be really sure it is available, and the TRBPTR may not
         * indicate the same. Also, affected cores are also affected by another
         * erratum which forces the PAGE_SIZE alignment on the TRBPTR, and thus
         * could potentially pad an entire PAGE_SIZE - 64bytes, to get those
         * 64bytes. Thus we ignore the potential triggering of the erratum
         * on WRAP and limit the data to LIMIT.
         */
        if (wrap)
                write = get_trbe_limit_pointer();
        else
                write = get_trbe_write_pointer();

        /*
         * TRBE may use a different base address than the base
         * of the ring buffer. Thus use the beginning of the ring
         * buffer to compute the offsets.
         */
        end_off = write - buf->trbe_base;
        start_off = PERF_IDX2OFF(handle->head, buf);

        if (WARN_ON_ONCE(end_off < start_off))
                return 0;

        size = end_off - start_off;
        /*
         * If the TRBE is affected by the following erratum, we must fill
         * the space we skipped with IGNORE packets. And we are always
         * guaranteed to have at least a PAGE_SIZE space in the buffer.
         */
        if (trbe_has_erratum(buf->cpudata, TRBE_WORKAROUND_OVERWRITE_FILL_MODE) &&
            !WARN_ON(size < overwrite_skip))
                __trbe_pad_buf(buf, start_off, overwrite_skip);

        return size;
}

static void *arm_trbe_alloc_buffer(struct coresight_device *csdev,
                                   struct perf_event *event, void **pages,
                                   int nr_pages, bool snapshot)
{
        struct trbe_buf *buf;
        struct page **pglist;
        int i;

        /*
         * TRBE LIMIT and TRBE WRITE pointers must be page aligned. But with
         * just a single page, there would not be any room left while writing
         * into a partially filled TRBE buffer after the page size alignment.
         * Hence restrict the minimum buffer size as two pages.
         */
        if (nr_pages < 2)
                return NULL;

        buf = kzalloc_node(sizeof(*buf), GFP_KERNEL, trbe_alloc_node(event));
        if (!buf)
                return ERR_PTR(-ENOMEM);

        pglist = kcalloc(nr_pages, sizeof(*pglist), GFP_KERNEL);
        if (!pglist) {
                kfree(buf);
                return ERR_PTR(-ENOMEM);
        }

        for (i = 0; i < nr_pages; i++)
                pglist[i] = virt_to_page(pages[i]);

        buf->trbe_base = (unsigned long)vmap(pglist, nr_pages, VM_MAP, PAGE_KERNEL);
        if (!buf->trbe_base) {
                kfree(pglist);
                kfree(buf);
                return ERR_PTR(-ENOMEM);
        }
        buf->trbe_limit = buf->trbe_base + nr_pages * PAGE_SIZE;
        buf->trbe_write = buf->trbe_base;
        buf->snapshot = snapshot;
        buf->nr_pages = nr_pages;
        buf->pages = pages;
        kfree(pglist);
        return buf;
}

static void arm_trbe_free_buffer(void *config)
{
        struct trbe_buf *buf = config;

        vunmap((void *)buf->trbe_base);
        kfree(buf);
}

static unsigned long arm_trbe_update_buffer(struct coresight_device *csdev,
                                            struct perf_output_handle *handle,
                                            void *config)
{
        struct trbe_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
        struct trbe_cpudata *cpudata = dev_get_drvdata(&csdev->dev);
        struct trbe_buf *buf = config;
        enum trbe_fault_action act;
        unsigned long size, status;
        unsigned long flags;
        bool wrap = false;

        WARN_ON(buf->cpudata != cpudata);
        WARN_ON(cpudata->cpu != smp_processor_id());
        WARN_ON(cpudata->drvdata != drvdata);
        if (cpudata->mode != CS_MODE_PERF)
                return 0;

        /*
         * We are about to disable the TRBE. And this could in turn
         * fill up the buffer triggering, an IRQ. This could be consumed
         * by the PE asynchronously, causing a race here against
         * the IRQ handler in closing out the handle. So, let us
         * make sure the IRQ can't trigger while we are collecting
         * the buffer. We also make sure that a WRAP event is handled
         * accordingly.
         */
        local_irq_save(flags);

        /*
         * If the TRBE was disabled due to lack of space in the AUX buffer or a
         * spurious fault, the driver leaves it disabled, truncating the buffer.
         * Since the etm_perf driver expects to close out the AUX buffer, the
         * driver skips it. Thus, just pass in 0 size here to indicate that the
         * buffer was truncated.
         */
        if (!is_trbe_enabled()) {
                size = 0;
                goto done;
        }
        /*
         * perf handle structure needs to be shared with the TRBE IRQ handler for
         * capturing trace data and restarting the handle. There is a probability
         * of an undefined reference based crash when etm event is being stopped
         * while a TRBE IRQ also getting processed. This happens due the release
         * of perf handle via perf_aux_output_end() in etm_event_stop(). Stopping
         * the TRBE here will ensure that no IRQ could be generated when the perf
         * handle gets freed in etm_event_stop().
         */
        trbe_drain_and_disable_local();

        /* Check if there is a pending interrupt and handle it here */
        status = read_sysreg_s(SYS_TRBSR_EL1);
        if (is_trbe_irq(status)) {

                /*
                 * Now that we are handling the IRQ here, clear the IRQ
                 * from the status, to let the irq handler know that it
                 * is taken care of.
                 */
                clr_trbe_irq();
                isb();

                act = trbe_get_fault_act(handle, status);
                /*
                 * If this was not due to a WRAP event, we have some
                 * errors and as such buffer is empty.
                 */
                if (act != TRBE_FAULT_ACT_WRAP) {
                        size = 0;
                        goto done;
                }

                trbe_report_wrap_event(handle);
                wrap = true;
        }

        size = trbe_get_trace_size(handle, buf, wrap);

done:
        local_irq_restore(flags);

        if (buf->snapshot)
                handle->head += size;
        return size;
}


static int trbe_apply_work_around_before_enable(struct trbe_buf *buf)
{
        /*
         * TRBE_WORKAROUND_OVERWRITE_FILL_MODE causes the TRBE to overwrite a few cache
         * line size from the "TRBBASER_EL1" in the event of a "FILL".
         * Thus, we could loose some amount of the trace at the base.
         *
         * Before Fix:
         *
         *  normal-BASE     head (normal-TRBPTR)         tail (normal-LIMIT)
         *  |                   \/                       /
         *   -------------------------------------------------------------
         *  |   Pg0      |   Pg1       |           |          |  PgN     |
         *   -------------------------------------------------------------
         *
         * In the normal course of action, we would set the TRBBASER to the
         * beginning of the ring-buffer (normal-BASE). But with the erratum,
         * the TRBE could overwrite the contents at the "normal-BASE", after
         * hitting the "normal-LIMIT", since it doesn't stop as expected. And
         * this is wrong. This could result in overwriting trace collected in
         * one of the previous runs, being consumed by the user. So we must
         * always make sure that the TRBBASER is within the region
         * [head, head+size]. Note that TRBBASER must be PAGE aligned,
         *
         *  After moving the BASE:
         *
         *  normal-BASE     head (normal-TRBPTR)         tail (normal-LIMIT)
         *  |                   \/                       /
         *   -------------------------------------------------------------
         *  |         |          |xyzdef.     |..   tuvw|                |
         *   -------------------------------------------------------------
         *                      /
         *              New-BASER
         *
         * Also, we would set the TRBPTR to head (after adjusting for
         * alignment) at normal-PTR. This would mean that the last few bytes
         * of the trace (say, "xyz") might overwrite the first few bytes of
         * trace written ("abc"). More importantly they will appear in what
         * userspace sees as the beginning of the trace, which is wrong. We may
         * not always have space to move the latest trace "xyz" to the correct
         * order as it must appear beyond the LIMIT. (i.e, [head..head+size]).
         * Thus it is easier to ignore those bytes than to complicate the
         * driver to move it, assuming that the erratum was triggered and
         * doing additional checks to see if there is indeed allowed space at
         * TRBLIMITR.LIMIT.
         *
         *  Thus the full workaround will move the BASE and the PTR and would
         *  look like (after padding at the skipped bytes at the end of
         *  session) :
         *
         *  normal-BASE     head (normal-TRBPTR)         tail (normal-LIMIT)
         *  |                   \/                       /
         *   -------------------------------------------------------------
         *  |         |          |///abc..     |..  rst|                |
         *   -------------------------------------------------------------
         *                      /    |
         *              New-BASER    New-TRBPTR
         *
         * To summarize, with the work around:
         *
         *  - We always align the offset for the next session to PAGE_SIZE
         *    (This is to ensure we can program the TRBBASER to this offset
         *    within the region [head...head+size]).
         *
         *  - At TRBE enable:
         *     - Set the TRBBASER to the page aligned offset of the current
         *       proposed write offset. (which is guaranteed to be aligned
         *       as above)
         *     - Move the TRBPTR to skip first 256bytes (that might be
         *       overwritten with the erratum). This ensures that the trace
         *       generated in the session is not re-written.
         *
         *  - At trace collection:
         *     - Pad the 256bytes skipped above again with IGNORE packets.
         */
        if (trbe_has_erratum(buf->cpudata, TRBE_WORKAROUND_OVERWRITE_FILL_MODE)) {
                if (WARN_ON(!IS_ALIGNED(buf->trbe_write, PAGE_SIZE)))
                        return -EINVAL;
                buf->trbe_hw_base = buf->trbe_write;
                buf->trbe_write += TRBE_WORKAROUND_OVERWRITE_FILL_MODE_SKIP_BYTES;
        }

        /*
         * TRBE_WORKAROUND_WRITE_OUT_OF_RANGE could cause the TRBE to write to
         * the next page after the TRBLIMITR.LIMIT. For perf, the "next page"
         * may be:
         *     - The page beyond the ring buffer. This could mean, TRBE could
         *       corrupt another entity (kernel / user)
         *     - A portion of the "ring buffer" consumed by the userspace.
         *       i.e, a page outisde [head, head + size].
         *
         * We work around this by:
         *     - Making sure that we have at least an extra space of PAGE left
         *       in the ring buffer [head, head + size], than we normally do
         *       without the erratum. See trbe_min_trace_buf_size().
         *
         *     - Adjust the TRBLIMITR.LIMIT to leave the extra PAGE outside
         *       the TRBE's range (i.e [TRBBASER, TRBLIMITR.LIMI] ).
         */
        if (trbe_has_erratum(buf->cpudata, TRBE_WORKAROUND_WRITE_OUT_OF_RANGE)) {
                s64 space = buf->trbe_limit - buf->trbe_write;
                /*
                 * We must have more than a PAGE_SIZE worth space in the proposed
                 * range for the TRBE.
                 */
                if (WARN_ON(space <= PAGE_SIZE ||
                            !IS_ALIGNED(buf->trbe_limit, PAGE_SIZE)))
                        return -EINVAL;
                buf->trbe_limit -= PAGE_SIZE;
        }

        return 0;
}

static int __arm_trbe_enable(struct trbe_buf *buf,
                             struct perf_output_handle *handle)
{
        int ret = 0;

        perf_aux_output_flag(handle, PERF_AUX_FLAG_CORESIGHT_FORMAT_RAW);
        buf->trbe_limit = compute_trbe_buffer_limit(handle);
        buf->trbe_write = buf->trbe_base + PERF_IDX2OFF(handle->head, buf);
        if (buf->trbe_limit == buf->trbe_base) {
                ret = -ENOSPC;
                goto err;
        }
        /* Set the base of the TRBE to the buffer base */
        buf->trbe_hw_base = buf->trbe_base;

        ret = trbe_apply_work_around_before_enable(buf);
        if (ret)
                goto err;

        *this_cpu_ptr(buf->cpudata->drvdata->handle) = handle;
        trbe_enable_hw(buf);
        return 0;
err:
        trbe_stop_and_truncate_event(handle);
        return ret;
}

static int arm_trbe_enable(struct coresight_device *csdev, u32 mode, void *data)
{
        struct trbe_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
        struct trbe_cpudata *cpudata = dev_get_drvdata(&csdev->dev);
        struct perf_output_handle *handle = data;
        struct trbe_buf *buf = etm_perf_sink_config(handle);

        WARN_ON(cpudata->cpu != smp_processor_id());
        WARN_ON(cpudata->drvdata != drvdata);
        if (mode != CS_MODE_PERF)
                return -EINVAL;

        cpudata->buf = buf;
        cpudata->mode = mode;
        buf->cpudata = cpudata;

        return __arm_trbe_enable(buf, handle);
}

static int arm_trbe_disable(struct coresight_device *csdev)
{
        struct trbe_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
        struct trbe_cpudata *cpudata = dev_get_drvdata(&csdev->dev);
        struct trbe_buf *buf = cpudata->buf;

        WARN_ON(buf->cpudata != cpudata);
        WARN_ON(cpudata->cpu != smp_processor_id());
        WARN_ON(cpudata->drvdata != drvdata);
        if (cpudata->mode != CS_MODE_PERF)
                return -EINVAL;

        trbe_drain_and_disable_local();
        buf->cpudata = NULL;
        cpudata->buf = NULL;
        cpudata->mode = CS_MODE_DISABLED;
        return 0;
}

static void trbe_handle_spurious(struct perf_output_handle *handle)
{
        u64 limitr = read_sysreg_s(SYS_TRBLIMITR_EL1);

        /*

         * If the IRQ was spurious, simply re-enable the TRBE
         * back without modifying the buffer parameters to
         * retain the trace collected so far.
         */
        limitr |= TRBLIMITR_ENABLE;
        write_sysreg_s(limitr, SYS_TRBLIMITR_EL1);
        isb();
}

static int trbe_handle_overflow(struct perf_output_handle *handle)
{
        struct perf_event *event = handle->event;
        struct trbe_buf *buf = etm_perf_sink_config(handle);
        unsigned long size;
        struct etm_event_data *event_data;

        size = trbe_get_trace_size(handle, buf, true);
        if (buf->snapshot)
                handle->head += size;

        trbe_report_wrap_event(handle);
        perf_aux_output_end(handle, size);
        event_data = perf_aux_output_begin(handle, event);
        if (!event_data) {
                /*
                 * We are unable to restart the trace collection,
                 * thus leave the TRBE disabled. The etm-perf driver
                 * is able to detect this with a disconnected handle
                 * (handle->event = NULL).
                 */
                trbe_drain_and_disable_local();
                *this_cpu_ptr(buf->cpudata->drvdata->handle) = NULL;
                return -EINVAL;
        }

        return __arm_trbe_enable(buf, handle);
}

static bool is_perf_trbe(struct perf_output_handle *handle)
{
        struct trbe_buf *buf = etm_perf_sink_config(handle);
        struct trbe_cpudata *cpudata = buf->cpudata;
        struct trbe_drvdata *drvdata = cpudata->drvdata;
        int cpu = smp_processor_id();

        WARN_ON(buf->trbe_hw_base != get_trbe_base_pointer());
        WARN_ON(buf->trbe_limit != get_trbe_limit_pointer());

        if (cpudata->mode != CS_MODE_PERF)
                return false;

        if (cpudata->cpu != cpu)
                return false;

        if (!cpumask_test_cpu(cpu, &drvdata->supported_cpus))
                return false;

        return true;
}

static irqreturn_t arm_trbe_irq_handler(int irq, void *dev)
{
        struct perf_output_handle **handle_ptr = dev;
        struct perf_output_handle *handle = *handle_ptr;
        enum trbe_fault_action act;
        u64 status;
        bool truncated = false;
        u64 trfcr;

        /* Reads to TRBSR_EL1 is fine when TRBE is active */
        status = read_sysreg_s(SYS_TRBSR_EL1);
        /*
         * If the pending IRQ was handled by update_buffer callback
         * we have nothing to do here.
         */
        if (!is_trbe_irq(status))
                return IRQ_NONE;

        /* Prohibit the CPU from tracing before we disable the TRBE */
        trfcr = cpu_prohibit_trace();
        /*
         * Ensure the trace is visible to the CPUs and
         * any external aborts have been resolved.
         */
        trbe_drain_and_disable_local();
        clr_trbe_irq();
        isb();

        if (WARN_ON_ONCE(!handle) || !perf_get_aux(handle))
                return IRQ_NONE;

        if (!is_perf_trbe(handle))
                return IRQ_NONE;

        act = trbe_get_fault_act(handle, status);
        switch (act) {
        case TRBE_FAULT_ACT_WRAP:
                truncated = !!trbe_handle_overflow(handle);
                break;
        case TRBE_FAULT_ACT_SPURIOUS:
                trbe_handle_spurious(handle);
                break;
        case TRBE_FAULT_ACT_FATAL:
                trbe_stop_and_truncate_event(handle);
                truncated = true;
                break;
        }

        /*
         * If the buffer was truncated, ensure perf callbacks
         * have completed, which will disable the event.
         *
         * Otherwise, restore the trace filter controls to
         * allow the tracing.
         */
        if (truncated)
                irq_work_run();
        else
                write_trfcr(trfcr);

        return IRQ_HANDLED;
}

static const struct coresight_ops_sink arm_trbe_sink_ops = {
        .enable         = arm_trbe_enable,
        .disable        = arm_trbe_disable,
        .alloc_buffer   = arm_trbe_alloc_buffer,
        .free_buffer    = arm_trbe_free_buffer,
        .update_buffer  = arm_trbe_update_buffer,
};

static const struct coresight_ops arm_trbe_cs_ops = {
        .sink_ops       = &arm_trbe_sink_ops,
};

static ssize_t align_show(struct device *dev, struct device_attribute *attr, char *buf)
{
        struct trbe_cpudata *cpudata = dev_get_drvdata(dev);

        return sprintf(buf, "%llx\n", cpudata->trbe_hw_align);
}
static DEVICE_ATTR_RO(align);

static ssize_t flag_show(struct device *dev, struct device_attribute *attr, char *buf)
{
        struct trbe_cpudata *cpudata = dev_get_drvdata(dev);

        return sprintf(buf, "%d\n", cpudata->trbe_flag);
}
static DEVICE_ATTR_RO(flag);

static struct attribute *arm_trbe_attrs[] = {
        &dev_attr_align.attr,
        &dev_attr_flag.attr,
        NULL,
};

static const struct attribute_group arm_trbe_group = {
        .attrs = arm_trbe_attrs,
};

static const struct attribute_group *arm_trbe_groups[] = {
        &arm_trbe_group,
        NULL,
};

static void arm_trbe_enable_cpu(void *info)
{
        struct trbe_drvdata *drvdata = info;

        trbe_reset_local();
        enable_percpu_irq(drvdata->irq, IRQ_TYPE_NONE);
}

static void arm_trbe_register_coresight_cpu(struct trbe_drvdata *drvdata, int cpu)
{
        struct trbe_cpudata *cpudata = per_cpu_ptr(drvdata->cpudata, cpu);
        struct coresight_device *trbe_csdev = coresight_get_percpu_sink(cpu);
        struct coresight_desc desc = { 0 };
        struct device *dev;

        if (WARN_ON(trbe_csdev))
                return;

        /* If the TRBE was not probed on the CPU, we shouldn't be here */
        if (WARN_ON(!cpudata->drvdata))
                return;

        dev = &cpudata->drvdata->pdev->dev;
        desc.name = devm_kasprintf(dev, GFP_KERNEL, "trbe%d", cpu);
        if (!desc.name)
                goto cpu_clear;

        desc.type = CORESIGHT_DEV_TYPE_SINK;
        desc.subtype.sink_subtype = CORESIGHT_DEV_SUBTYPE_SINK_PERCPU_SYSMEM;
        desc.ops = &arm_trbe_cs_ops;
        desc.pdata = dev_get_platdata(dev);
        desc.groups = arm_trbe_groups;
        desc.dev = dev;
        trbe_csdev = coresight_register(&desc);
        if (IS_ERR(trbe_csdev))
                goto cpu_clear;

        dev_set_drvdata(&trbe_csdev->dev, cpudata);
        coresight_set_percpu_sink(cpu, trbe_csdev);
        return;
cpu_clear:
        cpumask_clear_cpu(cpu, &drvdata->supported_cpus);
}

/*
 * Must be called with preemption disabled, for trbe_check_errata().
 */
static void arm_trbe_probe_cpu(void *info)
{
        struct trbe_drvdata *drvdata = info;
        int cpu = smp_processor_id();
        struct trbe_cpudata *cpudata = per_cpu_ptr(drvdata->cpudata, cpu);
        u64 trbidr;

        if (WARN_ON(!cpudata))
                goto cpu_clear;

        if (!is_trbe_available()) {
                pr_err("TRBE is not implemented on cpu %d\n", cpu);
                goto cpu_clear;
        }

        trbidr = read_sysreg_s(SYS_TRBIDR_EL1);
        if (!is_trbe_programmable(trbidr)) {
                pr_err("TRBE is owned in higher exception level on cpu %d\n", cpu);
                goto cpu_clear;
        }

        cpudata->trbe_hw_align = 1ULL << get_trbe_address_align(trbidr);
        if (cpudata->trbe_hw_align > SZ_2K) {
                pr_err("Unsupported alignment on cpu %d\n", cpu);
                goto cpu_clear;
        }

        /*
         * Run the TRBE erratum checks, now that we know
         * this instance is about to be registered.
         */
        trbe_check_errata(cpudata);

        /*
         * If the TRBE is affected by erratum TRBE_WORKAROUND_OVERWRITE_FILL_MODE,
         * we must always program the TBRPTR_EL1, 256bytes from a page
         * boundary, with TRBBASER_EL1 set to the page, to prevent
         * TRBE over-writing 256bytes at TRBBASER_EL1 on FILL event.
         *
         * Thus make sure we always align our write pointer to a PAGE_SIZE,
         * which also guarantees that we have at least a PAGE_SIZE space in
         * the buffer (TRBLIMITR is PAGE aligned) and thus we can skip
         * the required bytes at the base.
         */
        if (trbe_may_overwrite_in_fill_mode(cpudata))
                cpudata->trbe_align = PAGE_SIZE;
        else
                cpudata->trbe_align = cpudata->trbe_hw_align;

        cpudata->trbe_flag = get_trbe_flag_update(trbidr);
        cpudata->cpu = cpu;
        cpudata->drvdata = drvdata;
        return;
cpu_clear:
        cpumask_clear_cpu(cpu, &drvdata->supported_cpus);
}

static void arm_trbe_remove_coresight_cpu(void *info)
{
        int cpu = smp_processor_id();
        struct trbe_drvdata *drvdata = info;
        struct trbe_cpudata *cpudata = per_cpu_ptr(drvdata->cpudata, cpu);
        struct coresight_device *trbe_csdev = coresight_get_percpu_sink(cpu);

        disable_percpu_irq(drvdata->irq);
        trbe_reset_local();
        if (trbe_csdev) {
                coresight_unregister(trbe_csdev);
                cpudata->drvdata = NULL;
                coresight_set_percpu_sink(cpu, NULL);
        }
}

static int arm_trbe_probe_coresight(struct trbe_drvdata *drvdata)
{
        int cpu;

        drvdata->cpudata = alloc_percpu(typeof(*drvdata->cpudata));
        if (!drvdata->cpudata)
                return -ENOMEM;

        for_each_cpu(cpu, &drvdata->supported_cpus) {
                /* If we fail to probe the CPU, let us defer it to hotplug callbacks */
                if (smp_call_function_single(cpu, arm_trbe_probe_cpu, drvdata, 1))
                        continue;
                if (cpumask_test_cpu(cpu, &drvdata->supported_cpus))
                        arm_trbe_register_coresight_cpu(drvdata, cpu);
                if (cpumask_test_cpu(cpu, &drvdata->supported_cpus))
                        smp_call_function_single(cpu, arm_trbe_enable_cpu, drvdata, 1);
        }
        return 0;
}

static int arm_trbe_remove_coresight(struct trbe_drvdata *drvdata)
{
        int cpu;

        for_each_cpu(cpu, &drvdata->supported_cpus)
                smp_call_function_single(cpu, arm_trbe_remove_coresight_cpu, drvdata, 1);
        free_percpu(drvdata->cpudata);
        return 0;
}

static void arm_trbe_probe_hotplugged_cpu(struct trbe_drvdata *drvdata)
{
        preempt_disable();
        arm_trbe_probe_cpu(drvdata);
        preempt_enable();
}

static int arm_trbe_cpu_startup(unsigned int cpu, struct hlist_node *node)
{
        struct trbe_drvdata *drvdata = hlist_entry_safe(node, struct trbe_drvdata, hotplug_node);

        if (cpumask_test_cpu(cpu, &drvdata->supported_cpus)) {

                /*
                 * If this CPU was not probed for TRBE,
                 * initialize it now.
                 */
                if (!coresight_get_percpu_sink(cpu)) {
                        arm_trbe_probe_hotplugged_cpu(drvdata);
                        if (cpumask_test_cpu(cpu, &drvdata->supported_cpus))
                                arm_trbe_register_coresight_cpu(drvdata, cpu);
                        if (cpumask_test_cpu(cpu, &drvdata->supported_cpus))
                                arm_trbe_enable_cpu(drvdata);
                } else {
                        arm_trbe_enable_cpu(drvdata);
                }
        }
        return 0;
}

static int arm_trbe_cpu_teardown(unsigned int cpu, struct hlist_node *node)
{
        struct trbe_drvdata *drvdata = hlist_entry_safe(node, struct trbe_drvdata, hotplug_node);

        if (cpumask_test_cpu(cpu, &drvdata->supported_cpus)) {
                disable_percpu_irq(drvdata->irq);
                trbe_reset_local();
        }
        return 0;
}

static int arm_trbe_probe_cpuhp(struct trbe_drvdata *drvdata)
{
        enum cpuhp_state trbe_online;
        int ret;

        trbe_online = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN, DRVNAME,
                                              arm_trbe_cpu_startup, arm_trbe_cpu_teardown);
        if (trbe_online < 0)
                return trbe_online;

        ret = cpuhp_state_add_instance(trbe_online, &drvdata->hotplug_node);
        if (ret) {
                cpuhp_remove_multi_state(trbe_online);
                return ret;
        }
        drvdata->trbe_online = trbe_online;
        return 0;
}

static void arm_trbe_remove_cpuhp(struct trbe_drvdata *drvdata)
{
        cpuhp_remove_multi_state(drvdata->trbe_online);
}

static int arm_trbe_probe_irq(struct platform_device *pdev,
                              struct trbe_drvdata *drvdata)
{
        int ret;

        drvdata->irq = platform_get_irq(pdev, 0);
        if (drvdata->irq < 0) {
                pr_err("IRQ not found for the platform device\n");
                return drvdata->irq;
        }

        if (!irq_is_percpu(drvdata->irq)) {
                pr_err("IRQ is not a PPI\n");
                return -EINVAL;
        }

        if (irq_get_percpu_devid_partition(drvdata->irq, &drvdata->supported_cpus))
                return -EINVAL;

        drvdata->handle = alloc_percpu(struct perf_output_handle *);
        if (!drvdata->handle)
                return -ENOMEM;

        ret = request_percpu_irq(drvdata->irq, arm_trbe_irq_handler, DRVNAME, drvdata->handle);
        if (ret) {
                free_percpu(drvdata->handle);
                return ret;
        }
        return 0;
}

static void arm_trbe_remove_irq(struct trbe_drvdata *drvdata)
{
        free_percpu_irq(drvdata->irq, drvdata->handle);
        free_percpu(drvdata->handle);
}

static int arm_trbe_device_probe(struct platform_device *pdev)
{
        struct coresight_platform_data *pdata;
        struct trbe_drvdata *drvdata;
        struct device *dev = &pdev->dev;
        int ret;

        drvdata = devm_kzalloc(dev, sizeof(*drvdata), GFP_KERNEL);
        if (!drvdata)
                return -ENOMEM;

        pdata = coresight_get_platform_data(dev);
        if (IS_ERR(pdata))
                return PTR_ERR(pdata);

        dev_set_drvdata(dev, drvdata);
        dev->platform_data = pdata;
        drvdata->pdev = pdev;
        ret = arm_trbe_probe_irq(pdev, drvdata);
        if (ret)
                return ret;

        ret = arm_trbe_probe_coresight(drvdata);
        if (ret)
                goto probe_failed;

        ret = arm_trbe_probe_cpuhp(drvdata);
        if (ret)
                goto cpuhp_failed;

        return 0;
cpuhp_failed:
        arm_trbe_remove_coresight(drvdata);
probe_failed:
        arm_trbe_remove_irq(drvdata);
        return ret;
}

static int arm_trbe_device_remove(struct platform_device *pdev)
{
        struct trbe_drvdata *drvdata = platform_get_drvdata(pdev);

        arm_trbe_remove_cpuhp(drvdata);
        arm_trbe_remove_coresight(drvdata);
        arm_trbe_remove_irq(drvdata);
        return 0;
}

static const struct of_device_id arm_trbe_of_match[] = {
        { .compatible = "arm,trace-buffer-extension"},
        {},
};
MODULE_DEVICE_TABLE(of, arm_trbe_of_match);

static struct platform_driver arm_trbe_driver = {
        .driver = {
                .name = DRVNAME,
                .of_match_table = of_match_ptr(arm_trbe_of_match),
                .suppress_bind_attrs = true,
        },
        .probe  = arm_trbe_device_probe,
        .remove = arm_trbe_device_remove,
};

static int __init arm_trbe_init(void)
{
        int ret;

        if (arm64_kernel_unmapped_at_el0()) {
                pr_err("TRBE wouldn't work if kernel gets unmapped at EL0\n");
                return -EOPNOTSUPP;
        }

        ret = platform_driver_register(&arm_trbe_driver);
        if (!ret)
                return 0;

        pr_err("Error registering %s platform driver\n", DRVNAME);
        return ret;
}

static void __exit arm_trbe_exit(void)
{
        platform_driver_unregister(&arm_trbe_driver);
}
module_init(arm_trbe_init);
module_exit(arm_trbe_exit);

MODULE_AUTHOR("Anshuman Khandual <anshuman.khandual@arm.com>");
MODULE_DESCRIPTION("Arm Trace Buffer Extension (TRBE) driver");
MODULE_LICENSE("GPL v2");