/*
 * Copyright 2016-17 IBM Corp.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#define pr_fmt(fmt) "vas: " fmt

#include <linux/types.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/io.h>
#include <linux/log2.h>
#include <linux/rcupdate.h>
#include <linux/cred.h>
#include <asm/switch_to.h>
#include <asm/ppc-opcode.h>
#include "vas.h"
#include "copy-paste.h"

#define CREATE_TRACE_POINTS
#include "vas-trace.h"

/*
 * Compute the paste address region for the window @window using the
 * ->paste_base_addr and ->paste_win_id_shift we got from device tree.
 */
static void compute_paste_address(struct vas_window *window, u64 *addr, int *len)
{
        int winid;
        u64 base, shift;

        base = window->vinst->paste_base_addr;
        shift = window->vinst->paste_win_id_shift;
        winid = window->winid;

        *addr  = base + (winid << shift);
        if (len)
                *len = PAGE_SIZE;

        pr_debug("Txwin #%d: Paste addr 0x%llx\n", winid, *addr);
}

u64 vas_win_paste_addr(struct vas_window *win)
{
        u64 addr;

        compute_paste_address(win, &addr, NULL);

        return addr;
}
EXPORT_SYMBOL(vas_win_paste_addr);

static inline void get_hvwc_mmio_bar(struct vas_window *window,
                        u64 *start, int *len)
{
        u64 pbaddr;

        pbaddr = window->vinst->hvwc_bar_start;
        *start = pbaddr + window->winid * VAS_HVWC_SIZE;
        *len = VAS_HVWC_SIZE;
}

static inline void get_uwc_mmio_bar(struct vas_window *window,
                        u64 *start, int *len)
{
        u64 pbaddr;

        pbaddr = window->vinst->uwc_bar_start;
        *start = pbaddr + window->winid * VAS_UWC_SIZE;
        *len = VAS_UWC_SIZE;
}

/*
 * Map the paste bus address of the given send window into kernel address
 * space. Unlike MMIO regions (map_mmio_region() below), paste region must
 * be mapped cache-able and is only applicable to send windows.
 */
static void *map_paste_region(struct vas_window *txwin)
{
        int len;
        void *map;
        char *name;
        u64 start;

        name = kasprintf(GFP_KERNEL, "window-v%d-w%d", txwin->vinst->vas_id,
                                txwin->winid);
        if (!name)
                goto free_name;

        txwin->paste_addr_name = name;
        compute_paste_address(txwin, &start, &len);

        if (!request_mem_region(start, len, name)) {
                pr_devel("%s(): request_mem_region(0x%llx, %d) failed\n",
                                __func__, start, len);
                goto free_name;
        }

        map = ioremap_cache(start, len);
        if (!map) {
                pr_devel("%s(): ioremap_cache(0x%llx, %d) failed\n", __func__,
                                start, len);
                goto free_name;
        }

        pr_devel("Mapped paste addr 0x%llx to kaddr 0x%p\n", start, map);
        return map;

free_name:
        kfree(name);
        return ERR_PTR(-ENOMEM);
}

static void *map_mmio_region(char *name, u64 start, int len)
{
        void *map;

        if (!request_mem_region(start, len, name)) {
                pr_devel("%s(): request_mem_region(0x%llx, %d) failed\n",
                                __func__, start, len);
                return NULL;
        }

        map = ioremap(start, len);
        if (!map) {
                pr_devel("%s(): ioremap(0x%llx, %d) failed\n", __func__, start,
                                len);
                return NULL;
        }

        return map;
}

static void unmap_region(void *addr, u64 start, int len)
{
        iounmap(addr);
        release_mem_region((phys_addr_t)start, len);
}

/*
 * Unmap the paste address region for a window.
 */
static void unmap_paste_region(struct vas_window *window)
{
        int len;
        u64 busaddr_start;

        if (window->paste_kaddr) {
                compute_paste_address(window, &busaddr_start, &len);
                unmap_region(window->paste_kaddr, busaddr_start, len);
                window->paste_kaddr = NULL;
                kfree(window->paste_addr_name);
                window->paste_addr_name = NULL;
        }
}

/*
 * Unmap the MMIO regions for a window. Hold the vas_mutex so we don't
 * unmap when the window's debugfs dir is in use. This serializes close
 * of a window even on another VAS instance but since its not a critical
 * path, just minimize the time we hold the mutex for now. We can add
 * a per-instance mutex later if necessary.
 */
static void unmap_winctx_mmio_bars(struct vas_window *window)
{
        int len;
        void *uwc_map;
        void *hvwc_map;
        u64 busaddr_start;

        mutex_lock(&vas_mutex);

        hvwc_map = window->hvwc_map;
        window->hvwc_map = NULL;

        uwc_map = window->uwc_map;
        window->uwc_map = NULL;

        mutex_unlock(&vas_mutex);

        if (hvwc_map) {
                get_hvwc_mmio_bar(window, &busaddr_start, &len);
                unmap_region(hvwc_map, busaddr_start, len);
        }

        if (uwc_map) {
                get_uwc_mmio_bar(window, &busaddr_start, &len);
                unmap_region(uwc_map, busaddr_start, len);
        }
}

/*
 * Find the Hypervisor Window Context (HVWC) MMIO Base Address Region and the
 * OS/User Window Context (UWC) MMIO Base Address Region for the given window.
 * Map these bus addresses and save the mapped kernel addresses in @window.
 */
int map_winctx_mmio_bars(struct vas_window *window)
{
        int len;
        u64 start;

        get_hvwc_mmio_bar(window, &start, &len);
        window->hvwc_map = map_mmio_region("HVWCM_Window", start, len);

        get_uwc_mmio_bar(window, &start, &len);
        window->uwc_map = map_mmio_region("UWCM_Window", start, len);

        if (!window->hvwc_map || !window->uwc_map) {
                unmap_winctx_mmio_bars(window);
                return -1;
        }

        return 0;
}

/*
 * Reset all valid registers in the HV and OS/User Window Contexts for
 * the window identified by @window.
 *
 * NOTE: We cannot really use a for loop to reset window context. Not all
 *       offsets in a window context are valid registers and the valid
 *       registers are not sequential. And, we can only write to offsets
 *       with valid registers.
 */
void reset_window_regs(struct vas_window *window)
{
        write_hvwc_reg(window, VREG(LPID), 0ULL);
        write_hvwc_reg(window, VREG(PID), 0ULL);
        write_hvwc_reg(window, VREG(XLATE_MSR), 0ULL);
        write_hvwc_reg(window, VREG(XLATE_LPCR), 0ULL);
        write_hvwc_reg(window, VREG(XLATE_CTL), 0ULL);
        write_hvwc_reg(window, VREG(AMR), 0ULL);
        write_hvwc_reg(window, VREG(SEIDR), 0ULL);
        write_hvwc_reg(window, VREG(FAULT_TX_WIN), 0ULL);
        write_hvwc_reg(window, VREG(OSU_INTR_SRC_RA), 0ULL);
        write_hvwc_reg(window, VREG(HV_INTR_SRC_RA), 0ULL);
        write_hvwc_reg(window, VREG(PSWID), 0ULL);
        write_hvwc_reg(window, VREG(LFIFO_BAR), 0ULL);
        write_hvwc_reg(window, VREG(LDATA_STAMP_CTL), 0ULL);
        write_hvwc_reg(window, VREG(LDMA_CACHE_CTL), 0ULL);
        write_hvwc_reg(window, VREG(LRFIFO_PUSH), 0ULL);
        write_hvwc_reg(window, VREG(CURR_MSG_COUNT), 0ULL);
        write_hvwc_reg(window, VREG(LNOTIFY_AFTER_COUNT), 0ULL);
        write_hvwc_reg(window, VREG(LRX_WCRED), 0ULL);
        write_hvwc_reg(window, VREG(LRX_WCRED_ADDER), 0ULL);
        write_hvwc_reg(window, VREG(TX_WCRED), 0ULL);
        write_hvwc_reg(window, VREG(TX_WCRED_ADDER), 0ULL);
        write_hvwc_reg(window, VREG(LFIFO_SIZE), 0ULL);
        write_hvwc_reg(window, VREG(WINCTL), 0ULL);
        write_hvwc_reg(window, VREG(WIN_STATUS), 0ULL);
        write_hvwc_reg(window, VREG(WIN_CTX_CACHING_CTL), 0ULL);
        write_hvwc_reg(window, VREG(TX_RSVD_BUF_COUNT), 0ULL);
        write_hvwc_reg(window, VREG(LRFIFO_WIN_PTR), 0ULL);
        write_hvwc_reg(window, VREG(LNOTIFY_CTL), 0ULL);
        write_hvwc_reg(window, VREG(LNOTIFY_PID), 0ULL);
        write_hvwc_reg(window, VREG(LNOTIFY_LPID), 0ULL);
        write_hvwc_reg(window, VREG(LNOTIFY_TID), 0ULL);
        write_hvwc_reg(window, VREG(LNOTIFY_SCOPE), 0ULL);
        write_hvwc_reg(window, VREG(NX_UTIL_ADDER), 0ULL);

        /* Skip read-only registers: NX_UTIL and NX_UTIL_SE */

        /*
         * The send and receive window credit adder registers are also
         * accessible from HVWC and have been initialized above. We don't
         * need to initialize from the OS/User Window Context, so skip
         * following calls:
         *
         *      write_uwc_reg(window, VREG(TX_WCRED_ADDER), 0ULL);
         *      write_uwc_reg(window, VREG(LRX_WCRED_ADDER), 0ULL);
         */
}

/*
 * Initialize window context registers related to Address Translation.
 * These registers are common to send/receive windows although they
 * differ for user/kernel windows. As we resolve the TODOs we may
 * want to add fields to vas_winctx and move the initialization to
 * init_vas_winctx_regs().
 */
static void init_xlate_regs(struct vas_window *window, bool user_win)
{
        u64 lpcr, val;

        /*
         * MSR_TA, MSR_US are false for both kernel and user.
         * MSR_DR and MSR_PR are false for kernel.
         */
        val = 0ULL;
        val = SET_FIELD(VAS_XLATE_MSR_HV, val, 1);
        val = SET_FIELD(VAS_XLATE_MSR_SF, val, 1);
        if (user_win) {
                val = SET_FIELD(VAS_XLATE_MSR_DR, val, 1);
                val = SET_FIELD(VAS_XLATE_MSR_PR, val, 1);
        }
        write_hvwc_reg(window, VREG(XLATE_MSR), val);

        lpcr = mfspr(SPRN_LPCR);
        val = 0ULL;
        /*
         * NOTE: From Section 5.7.8.1 Segment Lookaside Buffer of the
         *       Power ISA, v3.0B, Page size encoding is 0 = 4KB, 5 = 64KB.
         *
         * NOTE: From Section 1.3.1, Address Translation Context of the
         *       Nest MMU Workbook, LPCR_SC should be 0 for Power9.
         */
        val = SET_FIELD(VAS_XLATE_LPCR_PAGE_SIZE, val, 5);
        val = SET_FIELD(VAS_XLATE_LPCR_ISL, val, lpcr & LPCR_ISL);
        val = SET_FIELD(VAS_XLATE_LPCR_TC, val, lpcr & LPCR_TC);
        val = SET_FIELD(VAS_XLATE_LPCR_SC, val, 0);
        write_hvwc_reg(window, VREG(XLATE_LPCR), val);

        /*
         * Section 1.3.1 (Address translation Context) of NMMU workbook.
         *      0b00    Hashed Page Table mode
         *      0b01    Reserved
         *      0b10    Radix on HPT
         *      0b11    Radix on Radix
         */
        val = 0ULL;
        val = SET_FIELD(VAS_XLATE_MODE, val, radix_enabled() ? 3 : 2);
        write_hvwc_reg(window, VREG(XLATE_CTL), val);

        /*
         * TODO: Can we mfspr(AMR) even for user windows?
         */
        val = 0ULL;
        val = SET_FIELD(VAS_AMR, val, mfspr(SPRN_AMR));
        write_hvwc_reg(window, VREG(AMR), val);

        val = 0ULL;
        val = SET_FIELD(VAS_SEIDR, val, 0);
        write_hvwc_reg(window, VREG(SEIDR), val);
}

/*
 * Initialize Reserved Send Buffer Count for the send window. It involves
 * writing to the register, reading it back to confirm that the hardware
 * has enough buffers to reserve. See section 1.3.1.2.1 of VAS workbook.
 *
 * Since we can only make a best-effort attempt to fulfill the request,
 * we don't return any errors if we cannot.
 *
 * TODO: Reserved (aka dedicated) send buffers are not supported yet.
 */
static void init_rsvd_tx_buf_count(struct vas_window *txwin,
                                struct vas_winctx *winctx)
{
        write_hvwc_reg(txwin, VREG(TX_RSVD_BUF_COUNT), 0ULL);
}

/*
 * init_winctx_regs()
 *      Initialize window context registers for a receive window.
 *      Except for caching control and marking window open, the registers
 *      are initialized in the order listed in Section 3.1.4 (Window Context
 *      Cache Register Details) of the VAS workbook although they don't need
 *      to be.
 *
 * Design note: For NX receive windows, NX allocates the FIFO buffer in OPAL
 *      (so that it can get a large contiguous area) and passes that buffer
 *      to kernel via device tree. We now write that buffer address to the
 *      FIFO BAR. Would it make sense to do this all in OPAL? i.e have OPAL
 *      write the per-chip RX FIFO addresses to the windows during boot-up
 *      as a one-time task? That could work for NX but what about other
 *      receivers?  Let the receivers tell us the rx-fifo buffers for now.
 */
int init_winctx_regs(struct vas_window *window, struct vas_winctx *winctx)
{
        u64 val;
        int fifo_size;

        reset_window_regs(window);

        val = 0ULL;
        val = SET_FIELD(VAS_LPID, val, winctx->lpid);
        write_hvwc_reg(window, VREG(LPID), val);

        val = 0ULL;
        val = SET_FIELD(VAS_PID_ID, val, winctx->pidr);
        write_hvwc_reg(window, VREG(PID), val);

        init_xlate_regs(window, winctx->user_win);

        val = 0ULL;
        val = SET_FIELD(VAS_FAULT_TX_WIN, val, 0);
        write_hvwc_reg(window, VREG(FAULT_TX_WIN), val);

        /* In PowerNV, interrupts go to HV. */
        write_hvwc_reg(window, VREG(OSU_INTR_SRC_RA), 0ULL);

        val = 0ULL;
        val = SET_FIELD(VAS_HV_INTR_SRC_RA, val, winctx->irq_port);
        write_hvwc_reg(window, VREG(HV_INTR_SRC_RA), val);

        val = 0ULL;
        val = SET_FIELD(VAS_PSWID_EA_HANDLE, val, winctx->pswid);
        write_hvwc_reg(window, VREG(PSWID), val);

        write_hvwc_reg(window, VREG(SPARE1), 0ULL);
        write_hvwc_reg(window, VREG(SPARE2), 0ULL);
        write_hvwc_reg(window, VREG(SPARE3), 0ULL);

        /*
         * NOTE: VAS expects the FIFO address to be copied into the LFIFO_BAR
         *       register as is - do NOT shift the address into VAS_LFIFO_BAR
         *       bit fields! Ok to set the page migration select fields -
         *       VAS ignores the lower 10+ bits in the address anyway, because
         *       the minimum FIFO size is 1K?
         *
         * See also: Design note in function header.
         */
        val = __pa(winctx->rx_fifo);
        val = SET_FIELD(VAS_PAGE_MIGRATION_SELECT, val, 0);
        write_hvwc_reg(window, VREG(LFIFO_BAR), val);

        val = 0ULL;
        val = SET_FIELD(VAS_LDATA_STAMP, val, winctx->data_stamp);
        write_hvwc_reg(window, VREG(LDATA_STAMP_CTL), val);

        val = 0ULL;
        val = SET_FIELD(VAS_LDMA_TYPE, val, winctx->dma_type);
        val = SET_FIELD(VAS_LDMA_FIFO_DISABLE, val, winctx->fifo_disable);
        write_hvwc_reg(window, VREG(LDMA_CACHE_CTL), val);

        write_hvwc_reg(window, VREG(LRFIFO_PUSH), 0ULL);
        write_hvwc_reg(window, VREG(CURR_MSG_COUNT), 0ULL);
        write_hvwc_reg(window, VREG(LNOTIFY_AFTER_COUNT), 0ULL);

        val = 0ULL;
        val = SET_FIELD(VAS_LRX_WCRED, val, winctx->wcreds_max);
        write_hvwc_reg(window, VREG(LRX_WCRED), val);

        val = 0ULL;
        val = SET_FIELD(VAS_TX_WCRED, val, winctx->wcreds_max);
        write_hvwc_reg(window, VREG(TX_WCRED), val);

        write_hvwc_reg(window, VREG(LRX_WCRED_ADDER), 0ULL);
        write_hvwc_reg(window, VREG(TX_WCRED_ADDER), 0ULL);

        fifo_size = winctx->rx_fifo_size / 1024;

        val = 0ULL;
        val = SET_FIELD(VAS_LFIFO_SIZE, val, ilog2(fifo_size));
        write_hvwc_reg(window, VREG(LFIFO_SIZE), val);

        /* Update window control and caching control registers last so
         * we mark the window open only after fully initializing it and
         * pushing context to cache.
         */

        write_hvwc_reg(window, VREG(WIN_STATUS), 0ULL);

        init_rsvd_tx_buf_count(window, winctx);

        /* for a send window, point to the matching receive window */
        val = 0ULL;
        val = SET_FIELD(VAS_LRX_WIN_ID, val, winctx->rx_win_id);
        write_hvwc_reg(window, VREG(LRFIFO_WIN_PTR), val);

        write_hvwc_reg(window, VREG(SPARE4), 0ULL);

        val = 0ULL;
        val = SET_FIELD(VAS_NOTIFY_DISABLE, val, winctx->notify_disable);
        val = SET_FIELD(VAS_INTR_DISABLE, val, winctx->intr_disable);
        val = SET_FIELD(VAS_NOTIFY_EARLY, val, winctx->notify_early);
        val = SET_FIELD(VAS_NOTIFY_OSU_INTR, val, winctx->notify_os_intr_reg);
        write_hvwc_reg(window, VREG(LNOTIFY_CTL), val);

        val = 0ULL;
        val = SET_FIELD(VAS_LNOTIFY_PID, val, winctx->lnotify_pid);
        write_hvwc_reg(window, VREG(LNOTIFY_PID), val);

        val = 0ULL;
        val = SET_FIELD(VAS_LNOTIFY_LPID, val, winctx->lnotify_lpid);
        write_hvwc_reg(window, VREG(LNOTIFY_LPID), val);

        val = 0ULL;
        val = SET_FIELD(VAS_LNOTIFY_TID, val, winctx->lnotify_tid);
        write_hvwc_reg(window, VREG(LNOTIFY_TID), val);

        val = 0ULL;
        val = SET_FIELD(VAS_LNOTIFY_MIN_SCOPE, val, winctx->min_scope);
        val = SET_FIELD(VAS_LNOTIFY_MAX_SCOPE, val, winctx->max_scope);
        write_hvwc_reg(window, VREG(LNOTIFY_SCOPE), val);

        /* Skip read-only registers NX_UTIL and NX_UTIL_SE */

        write_hvwc_reg(window, VREG(SPARE5), 0ULL);
        write_hvwc_reg(window, VREG(NX_UTIL_ADDER), 0ULL);
        write_hvwc_reg(window, VREG(SPARE6), 0ULL);

        /* Finally, push window context to memory and... */
        val = 0ULL;
        val = SET_FIELD(VAS_PUSH_TO_MEM, val, 1);
        write_hvwc_reg(window, VREG(WIN_CTX_CACHING_CTL), val);

        /* ... mark the window open for business */
        val = 0ULL;
        val = SET_FIELD(VAS_WINCTL_REJ_NO_CREDIT, val, winctx->rej_no_credit);
        val = SET_FIELD(VAS_WINCTL_PIN, val, winctx->pin_win);
        val = SET_FIELD(VAS_WINCTL_TX_WCRED_MODE, val, winctx->tx_wcred_mode);
        val = SET_FIELD(VAS_WINCTL_RX_WCRED_MODE, val, winctx->rx_wcred_mode);
        val = SET_FIELD(VAS_WINCTL_TX_WORD_MODE, val, winctx->tx_word_mode);
        val = SET_FIELD(VAS_WINCTL_RX_WORD_MODE, val, winctx->rx_word_mode);
        val = SET_FIELD(VAS_WINCTL_FAULT_WIN, val, winctx->fault_win);
        val = SET_FIELD(VAS_WINCTL_NX_WIN, val, winctx->nx_win);
        val = SET_FIELD(VAS_WINCTL_OPEN, val, 1);
        write_hvwc_reg(window, VREG(WINCTL), val);

        return 0;
}

static void vas_release_window_id(struct ida *ida, int winid)
{
        ida_free(ida, winid);
}

static int vas_assign_window_id(struct ida *ida)
{
        int winid = ida_alloc_max(ida, VAS_WINDOWS_PER_CHIP - 1, GFP_KERNEL);

        if (winid == -ENOSPC) {
                pr_err("Too many (%d) open windows\n", VAS_WINDOWS_PER_CHIP);
                return -EAGAIN;
        }

        return winid;
}

static void vas_window_free(struct vas_window *window)
{
        int winid = window->winid;
        struct vas_instance *vinst = window->vinst;

        unmap_winctx_mmio_bars(window);

        vas_window_free_dbgdir(window);

        kfree(window);

        vas_release_window_id(&vinst->ida, winid);
}

static struct vas_window *vas_window_alloc(struct vas_instance *vinst)
{
        int winid;
        struct vas_window *window;

        winid = vas_assign_window_id(&vinst->ida);
        if (winid < 0)
                return ERR_PTR(winid);

        window = kzalloc(sizeof(*window), GFP_KERNEL);
        if (!window)
                goto out_free;

        window->vinst = vinst;
        window->winid = winid;

        if (map_winctx_mmio_bars(window))
                goto out_free;

        vas_window_init_dbgdir(window);

        return window;

out_free:
        kfree(window);
        vas_release_window_id(&vinst->ida, winid);
        return ERR_PTR(-ENOMEM);
}

static void put_rx_win(struct vas_window *rxwin)
{
        /* Better not be a send window! */
        WARN_ON_ONCE(rxwin->tx_win);

        atomic_dec(&rxwin->num_txwins);
}

/*
 * Find the user space receive window given the @pswid.
 *      - We must have a valid vasid and it must belong to this instance.
 *        (so both send and receive windows are on the same VAS instance)
 *      - The window must refer to an OPEN, FTW, RECEIVE window.
 *
 * NOTE: We access ->windows[] table and assume that vinst->mutex is held.
 */
static struct vas_window *get_user_rxwin(struct vas_instance *vinst, u32 pswid)
{
        int vasid, winid;
        struct vas_window *rxwin;

        decode_pswid(pswid, &vasid, &winid);

        if (vinst->vas_id != vasid)
                return ERR_PTR(-EINVAL);

        rxwin = vinst->windows[winid];

        if (!rxwin || rxwin->tx_win || rxwin->cop != VAS_COP_TYPE_FTW)
                return ERR_PTR(-EINVAL);

        return rxwin;
}

/*
 * Get the VAS receive window associated with NX engine identified
 * by @cop and if applicable, @pswid.
 *
 * See also function header of set_vinst_win().
 */
static struct vas_window *get_vinst_rxwin(struct vas_instance *vinst,
                        enum vas_cop_type cop, u32 pswid)
{
        struct vas_window *rxwin;

        mutex_lock(&vinst->mutex);

        if (cop == VAS_COP_TYPE_FTW)
                rxwin = get_user_rxwin(vinst, pswid);
        else
                rxwin = vinst->rxwin[cop] ?: ERR_PTR(-EINVAL);

        if (!IS_ERR(rxwin))
                atomic_inc(&rxwin->num_txwins);

        mutex_unlock(&vinst->mutex);

        return rxwin;
}

/*
 * We have two tables of windows in a VAS instance. The first one,
 * ->windows[], contains all the windows in the instance and allows
 * looking up a window by its id. It is used to look up send windows
 * during fault handling and receive windows when pairing user space
 * send/receive windows.
 *
 * The second table, ->rxwin[], contains receive windows that are
 * associated with NX engines. This table has VAS_COP_TYPE_MAX
 * entries and is used to look up a receive window by its
 * coprocessor type.
 *
 * Here, we save @window in the ->windows[] table. If it is a receive
 * window, we also save the window in the ->rxwin[] table.
 */
static void set_vinst_win(struct vas_instance *vinst,
                        struct vas_window *window)
{
        int id = window->winid;

        mutex_lock(&vinst->mutex);

        /*
         * There should only be one receive window for a coprocessor type
         * unless its a user (FTW) window.
         */
        if (!window->user_win && !window->tx_win) {
                WARN_ON_ONCE(vinst->rxwin[window->cop]);
                vinst->rxwin[window->cop] = window;
        }

        WARN_ON_ONCE(vinst->windows[id] != NULL);
        vinst->windows[id] = window;

        mutex_unlock(&vinst->mutex);
}

/*
 * Clear this window from the table(s) of windows for this VAS instance.
 * See also function header of set_vinst_win().
 */
static void clear_vinst_win(struct vas_window *window)
{
        int id = window->winid;
        struct vas_instance *vinst = window->vinst;

        mutex_lock(&vinst->mutex);

        if (!window->user_win && !window->tx_win) {
                WARN_ON_ONCE(!vinst->rxwin[window->cop]);
                vinst->rxwin[window->cop] = NULL;
        }

        WARN_ON_ONCE(vinst->windows[id] != window);
        vinst->windows[id] = NULL;

        mutex_unlock(&vinst->mutex);
}

static void init_winctx_for_rxwin(struct vas_window *rxwin,
                        struct vas_rx_win_attr *rxattr,
                        struct vas_winctx *winctx)
{
        /*
         * We first zero (memset()) all fields and only set non-zero fields.
         * Following fields are 0/false but maybe deserve a comment:
         *
         *      ->notify_os_intr_reg    In powerNV, send intrs to HV
         *      ->notify_disable        False for NX windows
         *      ->intr_disable          False for Fault Windows
         *      ->xtra_write            False for NX windows
         *      ->notify_early          NA for NX windows
         *      ->rsvd_txbuf_count      NA for Rx windows
         *      ->lpid, ->pid, ->tid    NA for Rx windows
         */

        memset(winctx, 0, sizeof(struct vas_winctx));

        winctx->rx_fifo = rxattr->rx_fifo;
        winctx->rx_fifo_size = rxattr->rx_fifo_size;
        winctx->wcreds_max = rxwin->wcreds_max;
        winctx->pin_win = rxattr->pin_win;

        winctx->nx_win = rxattr->nx_win;
        winctx->fault_win = rxattr->fault_win;
        winctx->user_win = rxattr->user_win;
        winctx->rej_no_credit = rxattr->rej_no_credit;
        winctx->rx_word_mode = rxattr->rx_win_ord_mode;
        winctx->tx_word_mode = rxattr->tx_win_ord_mode;
        winctx->rx_wcred_mode = rxattr->rx_wcred_mode;
        winctx->tx_wcred_mode = rxattr->tx_wcred_mode;
        winctx->notify_early = rxattr->notify_early;

        if (winctx->nx_win) {
                winctx->data_stamp = true;
                winctx->intr_disable = true;
                winctx->pin_win = true;

                WARN_ON_ONCE(winctx->fault_win);
                WARN_ON_ONCE(!winctx->rx_word_mode);
                WARN_ON_ONCE(!winctx->tx_word_mode);
                WARN_ON_ONCE(winctx->notify_after_count);
        } else if (winctx->fault_win) {
                winctx->notify_disable = true;
        } else if (winctx->user_win) {
                /*
                 * Section 1.8.1 Low Latency Core-Core Wake up of
                 * the VAS workbook:
                 *
                 *      - disable credit checks ([tr]x_wcred_mode = false)
                 *      - disable FIFO writes
                 *      - enable ASB_Notify, disable interrupt
                 */
                winctx->fifo_disable = true;
                winctx->intr_disable = true;
                winctx->rx_fifo = NULL;
        }

        winctx->lnotify_lpid = rxattr->lnotify_lpid;
        winctx->lnotify_pid = rxattr->lnotify_pid;
        winctx->lnotify_tid = rxattr->lnotify_tid;
        winctx->pswid = rxattr->pswid;
        winctx->dma_type = VAS_DMA_TYPE_INJECT;
        winctx->tc_mode = rxattr->tc_mode;

        winctx->min_scope = VAS_SCOPE_LOCAL;
        winctx->max_scope = VAS_SCOPE_VECTORED_GROUP;
}

static bool rx_win_args_valid(enum vas_cop_type cop,
                        struct vas_rx_win_attr *attr)
{
        pr_debug("Rxattr: fault %d, notify %d, intr %d, early %d, fifo %d\n",
                        attr->fault_win, attr->notify_disable,
                        attr->intr_disable, attr->notify_early,
                        attr->rx_fifo_size);

        if (cop >= VAS_COP_TYPE_MAX)
                return false;

        if (cop != VAS_COP_TYPE_FTW &&
                                attr->rx_fifo_size < VAS_RX_FIFO_SIZE_MIN)
                return false;

        if (attr->rx_fifo_size > VAS_RX_FIFO_SIZE_MAX)
                return false;

        if (attr->wcreds_max > VAS_RX_WCREDS_MAX)
                return false;

        if (attr->nx_win) {
                /* cannot be fault or user window if it is nx */
                if (attr->fault_win || attr->user_win)
                        return false;
                /*
                 * Section 3.1.4.32: NX Windows must not disable notification,
                 *      and must not enable interrupts or early notification.
                 */
                if (attr->notify_disable || !attr->intr_disable ||
                                attr->notify_early)
                        return false;
        } else if (attr->fault_win) {
                /* cannot be both fault and user window */
                if (attr->user_win)
                        return false;

                /*
                 * Section 3.1.4.32: Fault windows must disable notification
                 *      but not interrupts.
                 */
                if (!attr->notify_disable || attr->intr_disable)
                        return false;

        } else if (attr->user_win) {
                /*
                 * User receive windows are only for fast-thread-wakeup
                 * (FTW). They don't need a FIFO and must disable interrupts
                 */
                if (attr->rx_fifo || attr->rx_fifo_size || !attr->intr_disable)
                        return false;
        } else {
                /* Rx window must be one of NX or Fault or User window. */
                return false;
        }

        return true;
}

void vas_init_rx_win_attr(struct vas_rx_win_attr *rxattr, enum vas_cop_type cop)
{
        memset(rxattr, 0, sizeof(*rxattr));

        if (cop == VAS_COP_TYPE_842 || cop == VAS_COP_TYPE_842_HIPRI) {
                rxattr->pin_win = true;
                rxattr->nx_win = true;
                rxattr->fault_win = false;
                rxattr->intr_disable = true;
                rxattr->rx_wcred_mode = true;
                rxattr->tx_wcred_mode = true;
                rxattr->rx_win_ord_mode = true;
                rxattr->tx_win_ord_mode = true;
        } else if (cop == VAS_COP_TYPE_FAULT) {
                rxattr->pin_win = true;
                rxattr->fault_win = true;
                rxattr->notify_disable = true;
                rxattr->rx_wcred_mode = true;
                rxattr->tx_wcred_mode = true;
                rxattr->rx_win_ord_mode = true;
                rxattr->tx_win_ord_mode = true;
        } else if (cop == VAS_COP_TYPE_FTW) {
                rxattr->user_win = true;
                rxattr->intr_disable = true;

                /*
                 * As noted in the VAS Workbook we disable credit checks.
                 * If we enable credit checks in the future, we must also
                 * implement a mechanism to return the user credits or new
                 * paste operations will fail.
                 */
        }
}
EXPORT_SYMBOL_GPL(vas_init_rx_win_attr);

struct vas_window *vas_rx_win_open(int vasid, enum vas_cop_type cop,
                        struct vas_rx_win_attr *rxattr)
{
        struct vas_window *rxwin;
        struct vas_winctx winctx;
        struct vas_instance *vinst;

        trace_vas_rx_win_open(current, vasid, cop, rxattr);

        if (!rx_win_args_valid(cop, rxattr))
                return ERR_PTR(-EINVAL);

        vinst = find_vas_instance(vasid);
        if (!vinst) {
                pr_devel("vasid %d not found!\n", vasid);
                return ERR_PTR(-EINVAL);
        }
        pr_devel("Found instance %d\n", vasid);

        rxwin = vas_window_alloc(vinst);
        if (IS_ERR(rxwin)) {
                pr_devel("Unable to allocate memory for Rx window\n");
                return rxwin;
        }

        rxwin->tx_win = false;
        rxwin->nx_win = rxattr->nx_win;
        rxwin->user_win = rxattr->user_win;
        rxwin->cop = cop;
        rxwin->wcreds_max = rxattr->wcreds_max ?: VAS_WCREDS_DEFAULT;
        if (rxattr->user_win)
                rxwin->pid = task_pid_vnr(current);

        init_winctx_for_rxwin(rxwin, rxattr, &winctx);
        init_winctx_regs(rxwin, &winctx);

        set_vinst_win(vinst, rxwin);

        return rxwin;
}
EXPORT_SYMBOL_GPL(vas_rx_win_open);

void vas_init_tx_win_attr(struct vas_tx_win_attr *txattr, enum vas_cop_type cop)
{
        memset(txattr, 0, sizeof(*txattr));

        if (cop == VAS_COP_TYPE_842 || cop == VAS_COP_TYPE_842_HIPRI) {
                txattr->rej_no_credit = false;
                txattr->rx_wcred_mode = true;
                txattr->tx_wcred_mode = true;
                txattr->rx_win_ord_mode = true;
                txattr->tx_win_ord_mode = true;
        } else if (cop == VAS_COP_TYPE_FTW) {
                txattr->user_win = true;
        }
}
EXPORT_SYMBOL_GPL(vas_init_tx_win_attr);

static void init_winctx_for_txwin(struct vas_window *txwin,
                        struct vas_tx_win_attr *txattr,
                        struct vas_winctx *winctx)
{
        /*
         * We first zero all fields and only set non-zero ones. Following
         * are some fields set to 0/false for the stated reason:
         *
         *      ->notify_os_intr_reg    In powernv, send intrs to HV
         *      ->rsvd_txbuf_count      Not supported yet.
         *      ->notify_disable        False for NX windows
         *      ->xtra_write            False for NX windows
         *      ->notify_early          NA for NX windows
         *      ->lnotify_lpid          NA for Tx windows
         *      ->lnotify_pid           NA for Tx windows
         *      ->lnotify_tid           NA for Tx windows
         *      ->tx_win_cred_mode      Ignore for now for NX windows
         *      ->rx_win_cred_mode      Ignore for now for NX windows
         */
        memset(winctx, 0, sizeof(struct vas_winctx));

        winctx->wcreds_max = txwin->wcreds_max;

        winctx->user_win = txattr->user_win;
        winctx->nx_win = txwin->rxwin->nx_win;
        winctx->pin_win = txattr->pin_win;
        winctx->rej_no_credit = txattr->rej_no_credit;
        winctx->rsvd_txbuf_enable = txattr->rsvd_txbuf_enable;

        winctx->rx_wcred_mode = txattr->rx_wcred_mode;
        winctx->tx_wcred_mode = txattr->tx_wcred_mode;
        winctx->rx_word_mode = txattr->rx_win_ord_mode;
        winctx->tx_word_mode = txattr->tx_win_ord_mode;
        winctx->rsvd_txbuf_count = txattr->rsvd_txbuf_count;

        winctx->intr_disable = true;
        if (winctx->nx_win)
                winctx->data_stamp = true;

        winctx->lpid = txattr->lpid;
        winctx->pidr = txattr->pidr;
        winctx->rx_win_id = txwin->rxwin->winid;

        winctx->dma_type = VAS_DMA_TYPE_INJECT;
        winctx->tc_mode = txattr->tc_mode;
        winctx->min_scope = VAS_SCOPE_LOCAL;
        winctx->max_scope = VAS_SCOPE_VECTORED_GROUP;

        winctx->pswid = 0;
}

static bool tx_win_args_valid(enum vas_cop_type cop,
                        struct vas_tx_win_attr *attr)
{
        if (attr->tc_mode != VAS_THRESH_DISABLED)
                return false;

        if (cop > VAS_COP_TYPE_MAX)
                return false;

        if (attr->wcreds_max > VAS_TX_WCREDS_MAX)
                return false;

        if (attr->user_win &&
                        (cop != VAS_COP_TYPE_FTW || attr->rsvd_txbuf_count))
                return false;

        return true;
}

struct vas_window *vas_tx_win_open(int vasid, enum vas_cop_type cop,
                        struct vas_tx_win_attr *attr)
{
        int rc;
        struct vas_window *txwin;
        struct vas_window *rxwin;
        struct vas_winctx winctx;
        struct vas_instance *vinst;

        trace_vas_tx_win_open(current, vasid, cop, attr);

        if (!tx_win_args_valid(cop, attr))

                return ERR_PTR(-EINVAL);

        /*
         * If caller did not specify a vasid but specified the PSWID of a
         * receive window (applicable only to FTW windows), use the vasid
         * from that receive window.
         */
        if (vasid == -1 && attr->pswid)
                decode_pswid(attr->pswid, &vasid, NULL);

        vinst = find_vas_instance(vasid);
        if (!vinst) {
                pr_devel("vasid %d not found!\n", vasid);
                return ERR_PTR(-EINVAL);
        }

        rxwin = get_vinst_rxwin(vinst, cop, attr->pswid);
        if (IS_ERR(rxwin)) {
                pr_devel("No RxWin for vasid %d, cop %d\n", vasid, cop);
                return rxwin;
        }

        txwin = vas_window_alloc(vinst);
        if (IS_ERR(txwin)) {
                rc = PTR_ERR(txwin);
                goto put_rxwin;
        }

        txwin->cop = cop;
        txwin->tx_win = 1;
        txwin->rxwin = rxwin;
        txwin->nx_win = txwin->rxwin->nx_win;
        txwin->pid = attr->pid;
        txwin->user_win = attr->user_win;
        txwin->wcreds_max = attr->wcreds_max ?: VAS_WCREDS_DEFAULT;

        init_winctx_for_txwin(txwin, attr, &winctx);

        init_winctx_regs(txwin, &winctx);

        /*
         * If its a kernel send window, map the window address into the
         * kernel's address space. For user windows, user must issue an
         * mmap() to map the window into their address space.
         *
         * NOTE: If kernel ever resubmits a user CRB after handling a page
         *       fault, we will need to map this into kernel as well.
         */
        if (!txwin->user_win) {
                txwin->paste_kaddr = map_paste_region(txwin);
                if (IS_ERR(txwin->paste_kaddr)) {
                        rc = PTR_ERR(txwin->paste_kaddr);
                        goto free_window;
                }
        } else {
                /*
                 * A user mapping must ensure that context switch issues
                 * CP_ABORT for this thread.
                 */
                rc = set_thread_uses_vas();
                if (rc)
                        goto free_window;
        }

        set_vinst_win(vinst, txwin);

        return txwin;

free_window:
        vas_window_free(txwin);

put_rxwin:
        put_rx_win(rxwin);
        return ERR_PTR(rc);

}
EXPORT_SYMBOL_GPL(vas_tx_win_open);

int vas_copy_crb(void *crb, int offset)
{
        return vas_copy(crb, offset);
}
EXPORT_SYMBOL_GPL(vas_copy_crb);

#define RMA_LSMP_REPORT_ENABLE PPC_BIT(53)
int vas_paste_crb(struct vas_window *txwin, int offset, bool re)
{
        int rc;
        void *addr;
        uint64_t val;

        trace_vas_paste_crb(current, txwin);

        /*
         * Only NX windows are supported for now and hardware assumes
         * report-enable flag is set for NX windows. Ensure software
         * complies too.
         */
        WARN_ON_ONCE(txwin->nx_win && !re);

        addr = txwin->paste_kaddr;
        if (re) {
                /*
                 * Set the REPORT_ENABLE bit (equivalent to writing
                 * to 1K offset of the paste address)
                 */
                val = SET_FIELD(RMA_LSMP_REPORT_ENABLE, 0ULL, 1);
                addr += val;
        }

        /*
         * Map the raw CR value from vas_paste() to an error code (there
         * is just pass or fail for now though).
         */
        rc = vas_paste(addr, offset);
        if (rc == 2)
                rc = 0;
        else
                rc = -EINVAL;

        pr_debug("Txwin #%d: Msg count %llu\n", txwin->winid,
                        read_hvwc_reg(txwin, VREG(LRFIFO_PUSH)));

        return rc;
}
EXPORT_SYMBOL_GPL(vas_paste_crb);

/*
 * If credit checking is enabled for this window, poll for the return
 * of window credits (i.e for NX engines to process any outstanding CRBs).
 * Since NX-842 waits for the CRBs to be processed before closing the
 * window, we should not have to wait for too long.
 *
 * TODO: We retry in 10ms intervals now. We could/should probably peek at
 *      the VAS_LRFIFO_PUSH_OFFSET register to get an estimate of pending
 *      CRBs on the FIFO and compute the delay dynamically on each retry.
 *      But that is not really needed until we support NX-GZIP access from
 *      user space. (NX-842 driver waits for CSB and Fast thread-wakeup
 *      doesn't use credit checking).
 */
static void poll_window_credits(struct vas_window *window)
{
        u64 val;
        int creds, mode;

        val = read_hvwc_reg(window, VREG(WINCTL));
        if (window->tx_win)
                mode = GET_FIELD(VAS_WINCTL_TX_WCRED_MODE, val);
        else
                mode = GET_FIELD(VAS_WINCTL_RX_WCRED_MODE, val);

        if (!mode)
                return;
retry:
        if (window->tx_win) {
                val = read_hvwc_reg(window, VREG(TX_WCRED));
                creds = GET_FIELD(VAS_TX_WCRED, val);
        } else {
                val = read_hvwc_reg(window, VREG(LRX_WCRED));
                creds = GET_FIELD(VAS_LRX_WCRED, val);
        }

        if (creds < window->wcreds_max) {
                val = 0;
                set_current_state(TASK_UNINTERRUPTIBLE);
                schedule_timeout(msecs_to_jiffies(10));
                goto retry;
        }
}

/*
 * Wait for the window to go to "not-busy" state. It should only take a
 * short time to queue a CRB, so window should not be busy for too long.
 * Trying 5ms intervals.
 */
static void poll_window_busy_state(struct vas_window *window)
{
        int busy;
        u64 val;

retry:
        val = read_hvwc_reg(window, VREG(WIN_STATUS));
        busy = GET_FIELD(VAS_WIN_BUSY, val);
        if (busy) {
                val = 0;
                set_current_state(TASK_UNINTERRUPTIBLE);
                schedule_timeout(msecs_to_jiffies(5));
                goto retry;
        }
}

/*
 * Have the hardware cast a window out of cache and wait for it to
 * be completed.
 *
 * NOTE: It can take a relatively long time to cast the window context
 *      out of the cache. It is not strictly necessary to cast out if:
 *
 *      - we clear the "Pin Window" bit (so hardware is free to evict)
 *
 *      - we re-initialize the window context when it is reassigned.
 *
 *      We do the former in vas_win_close() and latter in vas_win_open().
 *      So, ignoring the cast-out for now. We can add it as needed. If
 *      casting out becomes necessary we should consider offloading the
 *      job to a worker thread, so the window close can proceed quickly.
 */
static void poll_window_castout(struct vas_window *window)
{
        /* stub for now */
}

/*
 * Unpin and close a window so no new requests are accepted and the
 * hardware can evict this window from cache if necessary.
 */
static void unpin_close_window(struct vas_window *window)
{
        u64 val;

        val = read_hvwc_reg(window, VREG(WINCTL));
        val = SET_FIELD(VAS_WINCTL_PIN, val, 0);
        val = SET_FIELD(VAS_WINCTL_OPEN, val, 0);
        write_hvwc_reg(window, VREG(WINCTL), val);
}

/*
 * Close a window.
 *
 * See Section 1.12.1 of VAS workbook v1.05 for details on closing window:
 *      - Disable new paste operations (unmap paste address)
 *      - Poll for the "Window Busy" bit to be cleared
 *      - Clear the Open/Enable bit for the Window.
 *      - Poll for return of window Credits (implies FIFO empty for Rx win?)
 *      - Unpin and cast window context out of cache
 *
 * Besides the hardware, kernel has some bookkeeping of course.
 */
int vas_win_close(struct vas_window *window)
{
        if (!window)
                return 0;

        if (!window->tx_win && atomic_read(&window->num_txwins) != 0) {
                pr_devel("Attempting to close an active Rx window!\n");
                WARN_ON_ONCE(1);
                return -EBUSY;
        }

        unmap_paste_region(window);

        clear_vinst_win(window);

        poll_window_busy_state(window);

        unpin_close_window(window);

        poll_window_credits(window);

        poll_window_castout(window);

        /* if send window, drop reference to matching receive window */
        if (window->tx_win)
                put_rx_win(window->rxwin);

        vas_window_free(window);

        return 0;
}
EXPORT_SYMBOL_GPL(vas_win_close);

/*
 * Return a system-wide unique window id for the window @win.
 */
u32 vas_win_id(struct vas_window *win)
{
        return encode_pswid(win->vinst->vas_id, win->winid);
}
EXPORT_SYMBOL_GPL(vas_win_id);