/*
 * Copyright (c) 2017 Linaro Limited. All rights reserved.
 *
 * Author: Leo Yan <leo.yan@linaro.org>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published by
 * the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */
#include <linux/amba/bus.h>
#include <linux/coresight.h>
#include <linux/cpu.h>
#include <linux/debugfs.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/iopoll.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/pm_qos.h>
#include <linux/slab.h>
#include <linux/smp.h>
#include <linux/types.h>
#include <linux/uaccess.h>

#include "coresight-priv.h"

#define EDPCSR                          0x0A0
#define EDCIDSR                         0x0A4
#define EDVIDSR                         0x0A8
#define EDPCSR_HI                       0x0AC
#define EDOSLAR                         0x300
#define EDPRCR                          0x310
#define EDPRSR                          0x314
#define EDDEVID1                        0xFC4
#define EDDEVID                         0xFC8

#define EDPCSR_PROHIBITED               0xFFFFFFFF

/* bits definition for EDPCSR */
#define EDPCSR_THUMB                    BIT(0)
#define EDPCSR_ARM_INST_MASK            GENMASK(31, 2)
#define EDPCSR_THUMB_INST_MASK          GENMASK(31, 1)

/* bits definition for EDPRCR */
#define EDPRCR_COREPURQ                 BIT(3)
#define EDPRCR_CORENPDRQ                BIT(0)

/* bits definition for EDPRSR */
#define EDPRSR_DLK                      BIT(6)
#define EDPRSR_PU                       BIT(0)

/* bits definition for EDVIDSR */
#define EDVIDSR_NS                      BIT(31)
#define EDVIDSR_E2                      BIT(30)
#define EDVIDSR_E3                      BIT(29)
#define EDVIDSR_HV                      BIT(28)
#define EDVIDSR_VMID                    GENMASK(7, 0)

/*
 * bits definition for EDDEVID1:PSCROffset
 *
 * NOTE: armv8 and armv7 have different definition for the register,
 * so consolidate the bits definition as below:
 *
 * 0b0000 - Sample offset applies based on the instruction state, we
 *          rely on EDDEVID to check if EDPCSR is implemented or not
 * 0b0001 - No offset applies.
 * 0b0010 - No offset applies, but do not use in AArch32 mode
 *
 */
#define EDDEVID1_PCSR_OFFSET_MASK       GENMASK(3, 0)
#define EDDEVID1_PCSR_OFFSET_INS_SET    (0x0)
#define EDDEVID1_PCSR_NO_OFFSET_DIS_AARCH32     (0x2)

/* bits definition for EDDEVID */
#define EDDEVID_PCSAMPLE_MODE           GENMASK(3, 0)
#define EDDEVID_IMPL_EDPCSR             (0x1)
#define EDDEVID_IMPL_EDPCSR_EDCIDSR     (0x2)
#define EDDEVID_IMPL_FULL               (0x3)

#define DEBUG_WAIT_SLEEP                1000
#define DEBUG_WAIT_TIMEOUT              32000

struct debug_drvdata {
        void __iomem    *base;
        struct device   *dev;
        int             cpu;

        bool            edpcsr_present;
        bool            edcidsr_present;
        bool            edvidsr_present;
        bool            pc_has_offset;

        u32             edpcsr;
        u32             edpcsr_hi;
        u32             edprsr;
        u32             edvidsr;
        u32             edcidsr;
};

static DEFINE_MUTEX(debug_lock);
static DEFINE_PER_CPU(struct debug_drvdata *, debug_drvdata);
static int debug_count;
static struct dentry *debug_debugfs_dir;

static bool debug_enable;
module_param_named(enable, debug_enable, bool, 0600);
MODULE_PARM_DESC(enable, "Control to enable coresight CPU debug functionality");

static void debug_os_unlock(struct debug_drvdata *drvdata)
{
        /* Unlocks the debug registers */
        writel_relaxed(0x0, drvdata->base + EDOSLAR);

        /* Make sure the registers are unlocked before accessing */
        wmb();
}

/*
 * According to ARM DDI 0487A.k, before access external debug
 * registers should firstly check the access permission; if any
 * below condition has been met then cannot access debug
 * registers to avoid lockup issue:
 *
 * - CPU power domain is powered off;
 * - The OS Double Lock is locked;
 *
 * By checking EDPRSR can get to know if meet these conditions.
 */
static bool debug_access_permitted(struct debug_drvdata *drvdata)
{
        /* CPU is powered off */
        if (!(drvdata->edprsr & EDPRSR_PU))
                return false;

        /* The OS Double Lock is locked */
        if (drvdata->edprsr & EDPRSR_DLK)
                return false;

        return true;
}

static void debug_force_cpu_powered_up(struct debug_drvdata *drvdata)
{
        u32 edprcr;

try_again:

        /*
         * Send request to power management controller and assert
         * DBGPWRUPREQ signal; if power management controller has
         * sane implementation, it should enable CPU power domain
         * in case CPU is in low power state.
         */
        edprcr = readl_relaxed(drvdata->base + EDPRCR);
        edprcr |= EDPRCR_COREPURQ;
        writel_relaxed(edprcr, drvdata->base + EDPRCR);

        /* Wait for CPU to be powered up (timeout~=32ms) */
        if (readx_poll_timeout_atomic(readl_relaxed, drvdata->base + EDPRSR,
                        drvdata->edprsr, (drvdata->edprsr & EDPRSR_PU),
                        DEBUG_WAIT_SLEEP, DEBUG_WAIT_TIMEOUT)) {
                /*
                 * Unfortunately the CPU cannot be powered up, so return
                 * back and later has no permission to access other
                 * registers. For this case, should disable CPU low power
                 * states to ensure CPU power domain is enabled!
                 */
                dev_err(drvdata->dev, "%s: power up request for CPU%d failed\n",
                        __func__, drvdata->cpu);
                return;
        }

        /*
         * At this point the CPU is powered up, so set the no powerdown
         * request bit so we don't lose power and emulate power down.
         */
        edprcr = readl_relaxed(drvdata->base + EDPRCR);
        edprcr |= EDPRCR_COREPURQ | EDPRCR_CORENPDRQ;
        writel_relaxed(edprcr, drvdata->base + EDPRCR);

        drvdata->edprsr = readl_relaxed(drvdata->base + EDPRSR);

        /* The core power domain got switched off on use, try again */
        if (unlikely(!(drvdata->edprsr & EDPRSR_PU)))
                goto try_again;
}

static void debug_read_regs(struct debug_drvdata *drvdata)
{
        u32 save_edprcr;

        CS_UNLOCK(drvdata->base);

        /* Unlock os lock */
        debug_os_unlock(drvdata);

        /* Save EDPRCR register */
        save_edprcr = readl_relaxed(drvdata->base + EDPRCR);

        /*
         * Ensure CPU power domain is enabled to let registers
         * are accessiable.
         */
        debug_force_cpu_powered_up(drvdata);

        if (!debug_access_permitted(drvdata))
                goto out;

        drvdata->edpcsr = readl_relaxed(drvdata->base + EDPCSR);

        /*
         * As described in ARM DDI 0487A.k, if the processing
         * element (PE) is in debug state, or sample-based
         * profiling is prohibited, EDPCSR reads as 0xFFFFFFFF;
         * EDCIDSR, EDVIDSR and EDPCSR_HI registers also become
         * UNKNOWN state. So directly bail out for this case.
         */
        if (drvdata->edpcsr == EDPCSR_PROHIBITED)
                goto out;

        /*
         * A read of the EDPCSR normally has the side-effect of
         * indirectly writing to EDCIDSR, EDVIDSR and EDPCSR_HI;
         * at this point it's safe to read value from them.
         */
        if (IS_ENABLED(CONFIG_64BIT))
                drvdata->edpcsr_hi = readl_relaxed(drvdata->base + EDPCSR_HI);

        if (drvdata->edcidsr_present)
                drvdata->edcidsr = readl_relaxed(drvdata->base + EDCIDSR);

        if (drvdata->edvidsr_present)
                drvdata->edvidsr = readl_relaxed(drvdata->base + EDVIDSR);

out:
        /* Restore EDPRCR register */
        writel_relaxed(save_edprcr, drvdata->base + EDPRCR);

        CS_LOCK(drvdata->base);
}

#ifdef CONFIG_64BIT
static unsigned long debug_adjust_pc(struct debug_drvdata *drvdata)
{
        return (unsigned long)drvdata->edpcsr_hi << 32 |
               (unsigned long)drvdata->edpcsr;
}
#else
static unsigned long debug_adjust_pc(struct debug_drvdata *drvdata)
{
        unsigned long arm_inst_offset = 0, thumb_inst_offset = 0;
        unsigned long pc;

        pc = (unsigned long)drvdata->edpcsr;

        if (drvdata->pc_has_offset) {
                arm_inst_offset = 8;
                thumb_inst_offset = 4;
        }

        /* Handle thumb instruction */
        if (pc & EDPCSR_THUMB) {
                pc = (pc & EDPCSR_THUMB_INST_MASK) - thumb_inst_offset;
                return pc;
        }

        /*
         * Handle arm instruction offset, if the arm instruction
         * is not 4 byte alignment then it's possible the case
         * for implementation defined; keep original value for this
         * case and print info for notice.
         */
        if (pc & BIT(1))
                dev_emerg(drvdata->dev,
                          "Instruction offset is implementation defined\n");
        else
                pc = (pc & EDPCSR_ARM_INST_MASK) - arm_inst_offset;

        return pc;
}
#endif

static void debug_dump_regs(struct debug_drvdata *drvdata)
{
        struct device *dev = drvdata->dev;
        unsigned long pc;

        dev_emerg(dev, " EDPRSR:  %08x (Power:%s DLK:%s)\n",
                  drvdata->edprsr,
                  drvdata->edprsr & EDPRSR_PU ? "On" : "Off",
                  drvdata->edprsr & EDPRSR_DLK ? "Lock" : "Unlock");

        if (!debug_access_permitted(drvdata)) {
                dev_emerg(dev, "No permission to access debug registers!\n");
                return;
        }

        if (drvdata->edpcsr == EDPCSR_PROHIBITED) {
                dev_emerg(dev, "CPU is in Debug state or profiling is prohibited!\n");
                return;
        }

        pc = debug_adjust_pc(drvdata);
        dev_emerg(dev, " EDPCSR:  [<%px>] %pS\n", (void *)pc, (void *)pc);

        if (drvdata->edcidsr_present)
                dev_emerg(dev, " EDCIDSR: %08x\n", drvdata->edcidsr);

        if (drvdata->edvidsr_present)
                dev_emerg(dev, " EDVIDSR: %08x (State:%s Mode:%s Width:%dbits VMID:%x)\n",
                          drvdata->edvidsr,
                          drvdata->edvidsr & EDVIDSR_NS ?
                          "Non-secure" : "Secure",
                          drvdata->edvidsr & EDVIDSR_E3 ? "EL3" :
                                (drvdata->edvidsr & EDVIDSR_E2 ?
                                 "EL2" : "EL1/0"),
                          drvdata->edvidsr & EDVIDSR_HV ? 64 : 32,
                          drvdata->edvidsr & (u32)EDVIDSR_VMID);
}

static void debug_init_arch_data(void *info)
{
        struct debug_drvdata *drvdata = info;
        u32 mode, pcsr_offset;
        u32 eddevid, eddevid1;

        CS_UNLOCK(drvdata->base);

        /* Read device info */
        eddevid  = readl_relaxed(drvdata->base + EDDEVID);
        eddevid1 = readl_relaxed(drvdata->base + EDDEVID1);

        CS_LOCK(drvdata->base);

        /* Parse implementation feature */
        mode = eddevid & EDDEVID_PCSAMPLE_MODE;
        pcsr_offset = eddevid1 & EDDEVID1_PCSR_OFFSET_MASK;

        drvdata->edpcsr_present  = false;
        drvdata->edcidsr_present = false;
        drvdata->edvidsr_present = false;
        drvdata->pc_has_offset   = false;

        switch (mode) {
        case EDDEVID_IMPL_FULL:
                drvdata->edvidsr_present = true;
                /* Fall through */
        case EDDEVID_IMPL_EDPCSR_EDCIDSR:
                drvdata->edcidsr_present = true;
                /* Fall through */
        case EDDEVID_IMPL_EDPCSR:
                /*
                 * In ARM DDI 0487A.k, the EDDEVID1.PCSROffset is used to
                 * define if has the offset for PC sampling value; if read
                 * back EDDEVID1.PCSROffset == 0x2, then this means the debug
                 * module does not sample the instruction set state when
                 * armv8 CPU in AArch32 state.
                 */
                drvdata->edpcsr_present =
                        ((IS_ENABLED(CONFIG_64BIT) && pcsr_offset != 0) ||
                         (pcsr_offset != EDDEVID1_PCSR_NO_OFFSET_DIS_AARCH32));

                drvdata->pc_has_offset =
                        (pcsr_offset == EDDEVID1_PCSR_OFFSET_INS_SET);
                break;
        default:
                break;
        }
}

/*
 * Dump out information on panic.
 */
static int debug_notifier_call(struct notifier_block *self,
                               unsigned long v, void *p)
{
        int cpu;
        struct debug_drvdata *drvdata;

        mutex_lock(&debug_lock);

        /* Bail out if the functionality is disabled */
        if (!debug_enable)
                goto skip_dump;

        pr_emerg("ARM external debug module:\n");

        for_each_possible_cpu(cpu) {
                drvdata = per_cpu(debug_drvdata, cpu);
                if (!drvdata)
                        continue;

                dev_emerg(drvdata->dev, "CPU[%d]:\n", drvdata->cpu);

                debug_read_regs(drvdata);
                debug_dump_regs(drvdata);
        }

skip_dump:
        mutex_unlock(&debug_lock);
        return 0;
}

static struct notifier_block debug_notifier = {
        .notifier_call = debug_notifier_call,
};

static int debug_enable_func(void)
{
        struct debug_drvdata *drvdata;
        int cpu, ret = 0;
        cpumask_t mask;

        /*
         * Use cpumask to track which debug power domains have
         * been powered on and use it to handle failure case.
         */
        cpumask_clear(&mask);

        for_each_possible_cpu(cpu) {
                drvdata = per_cpu(debug_drvdata, cpu);
                if (!drvdata)
                        continue;

                ret = pm_runtime_get_sync(drvdata->dev);
                if (ret < 0)
                        goto err;
                else
                        cpumask_set_cpu(cpu, &mask);
        }

        return 0;

err:
        /*
         * If pm_runtime_get_sync() has failed, need rollback on
         * all the other CPUs that have been enabled before that.
         */
        for_each_cpu(cpu, &mask) {
                drvdata = per_cpu(debug_drvdata, cpu);
                pm_runtime_put_noidle(drvdata->dev);
        }

        return ret;
}

static int debug_disable_func(void)
{
        struct debug_drvdata *drvdata;
        int cpu, ret, err = 0;

        /*
         * Disable debug power domains, records the error and keep
         * circling through all other CPUs when an error has been
         * encountered.
         */
        for_each_possible_cpu(cpu) {
                drvdata = per_cpu(debug_drvdata, cpu);
                if (!drvdata)
                        continue;

                ret = pm_runtime_put(drvdata->dev);
                if (ret < 0)
                        err = ret;
        }

        return err;
}

static ssize_t debug_func_knob_write(struct file *f,
                const char __user *buf, size_t count, loff_t *ppos)
{
        u8 val;
        int ret;

        ret = kstrtou8_from_user(buf, count, 2, &val);
        if (ret)
                return ret;

        mutex_lock(&debug_lock);

        if (val == debug_enable)
                goto out;

        if (val)
                ret = debug_enable_func();
        else
                ret = debug_disable_func();

        if (ret) {
                pr_err("%s: unable to %s debug function: %d\n",
                       __func__, val ? "enable" : "disable", ret);
                goto err;
        }

        debug_enable = val;
out:
        ret = count;
err:
        mutex_unlock(&debug_lock);
        return ret;
}

static ssize_t debug_func_knob_read(struct file *f,
                char __user *ubuf, size_t count, loff_t *ppos)
{
        ssize_t ret;
        char buf[3];

        mutex_lock(&debug_lock);
        snprintf(buf, sizeof(buf), "%d\n", debug_enable);
        mutex_unlock(&debug_lock);

        ret = simple_read_from_buffer(ubuf, count, ppos, buf, sizeof(buf));
        return ret;
}

static const struct file_operations debug_func_knob_fops = {
        .open   = simple_open,
        .read   = debug_func_knob_read,
        .write  = debug_func_knob_write,
};

static int debug_func_init(void)
{
        struct dentry *file;
        int ret;

        /* Create debugfs node */
        debug_debugfs_dir = debugfs_create_dir("coresight_cpu_debug", NULL);
        if (!debug_debugfs_dir) {
                pr_err("%s: unable to create debugfs directory\n", __func__);
                return -ENOMEM;
        }

        file = debugfs_create_file("enable", 0644, debug_debugfs_dir, NULL,
                                   &debug_func_knob_fops);
        if (!file) {
                pr_err("%s: unable to create enable knob file\n", __func__);
                ret = -ENOMEM;
                goto err;
        }

        /* Register function to be called for panic */
        ret = atomic_notifier_chain_register(&panic_notifier_list,
                                             &debug_notifier);
        if (ret) {
                pr_err("%s: unable to register notifier: %d\n",
                       __func__, ret);
                goto err;
        }

        return 0;

err:
        debugfs_remove_recursive(debug_debugfs_dir);
        return ret;
}

static void debug_func_exit(void)
{
        atomic_notifier_chain_unregister(&panic_notifier_list,
                                         &debug_notifier);
        debugfs_remove_recursive(debug_debugfs_dir);
}

static int debug_probe(struct amba_device *adev, const struct amba_id *id)
{
        void __iomem *base;
        struct device *dev = &adev->dev;
        struct debug_drvdata *drvdata;
        struct resource *res = &adev->res;
        struct device_node *np = adev->dev.of_node;
        int ret;

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

        drvdata->cpu = np ? of_coresight_get_cpu(np) : 0;
        if (per_cpu(debug_drvdata, drvdata->cpu)) {
                dev_err(dev, "CPU%d drvdata has already been initialized\n",
                        drvdata->cpu);
                return -EBUSY;
        }

        drvdata->dev = &adev->dev;
        amba_set_drvdata(adev, drvdata);

        /* Validity for the resource is already checked by the AMBA core */
        base = devm_ioremap_resource(dev, res);
        if (IS_ERR(base))
                return PTR_ERR(base);

        drvdata->base = base;

        get_online_cpus();
        per_cpu(debug_drvdata, drvdata->cpu) = drvdata;
        ret = smp_call_function_single(drvdata->cpu, debug_init_arch_data,
                                       drvdata, 1);
        put_online_cpus();

        if (ret) {
                dev_err(dev, "CPU%d debug arch init failed\n", drvdata->cpu);
                goto err;
        }

        if (!drvdata->edpcsr_present) {
                dev_err(dev, "CPU%d sample-based profiling isn't implemented\n",
                        drvdata->cpu);
                ret = -ENXIO;
                goto err;
        }

        if (!debug_count++) {
                ret = debug_func_init();
                if (ret)
                        goto err_func_init;
        }

        mutex_lock(&debug_lock);
        /* Turn off debug power domain if debugging is disabled */
        if (!debug_enable)
                pm_runtime_put(dev);
        mutex_unlock(&debug_lock);

        dev_info(dev, "Coresight debug-CPU%d initialized\n", drvdata->cpu);
        return 0;

err_func_init:
        debug_count--;
err:
        per_cpu(debug_drvdata, drvdata->cpu) = NULL;
        return ret;
}

static int debug_remove(struct amba_device *adev)
{
        struct device *dev = &adev->dev;
        struct debug_drvdata *drvdata = amba_get_drvdata(adev);

        per_cpu(debug_drvdata, drvdata->cpu) = NULL;

        mutex_lock(&debug_lock);
        /* Turn off debug power domain before rmmod the module */
        if (debug_enable)
                pm_runtime_put(dev);
        mutex_unlock(&debug_lock);

        if (!--debug_count)
                debug_func_exit();

        return 0;
}

static const struct amba_id debug_ids[] = {
        {       /* Debug for Cortex-A53 */
                .id     = 0x000bbd03,
                .mask   = 0x000fffff,
        },
        {       /* Debug for Cortex-A57 */
                .id     = 0x000bbd07,
                .mask   = 0x000fffff,
        },
        {       /* Debug for Cortex-A72 */
                .id     = 0x000bbd08,
                .mask   = 0x000fffff,
        },
        { 0, 0 },
};

static struct amba_driver debug_driver = {
        .drv = {
                .name   = "coresight-cpu-debug",
                .suppress_bind_attrs = true,
        },
        .probe          = debug_probe,
        .remove         = debug_remove,
        .id_table       = debug_ids,
};

module_amba_driver(debug_driver);

MODULE_AUTHOR("Leo Yan <leo.yan@linaro.org>");
MODULE_DESCRIPTION("ARM Coresight CPU Debug Driver");
MODULE_LICENSE("GPL");