/*
 * Copyright © 2014 Intel Corporation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 */

/**
 * DOC: Frame Buffer Compression (FBC)
 *
 * FBC tries to save memory bandwidth (and so power consumption) by
 * compressing the amount of memory used by the display. It is total
 * transparent to user space and completely handled in the kernel.
 *
 * The benefits of FBC are mostly visible with solid backgrounds and
 * variation-less patterns. It comes from keeping the memory footprint small
 * and having fewer memory pages opened and accessed for refreshing the display.
 *
 * i915 is responsible to reserve stolen memory for FBC and configure its
 * offset on proper registers. The hardware takes care of all
 * compress/decompress. However there are many known cases where we have to
 * forcibly disable it to allow proper screen updates.
 */

#include <drm/drm_fourcc.h>

#include "i915_drv.h"
#include "i915_trace.h"
#include "i915_vgpu.h"
#include "intel_de.h"
#include "intel_display_types.h"
#include "intel_fbc.h"
#include "intel_frontbuffer.h"

/*
 * For SKL+, the plane source size used by the hardware is based on the value we
 * write to the PLANE_SIZE register. For BDW-, the hardware looks at the value
 * we wrote to PIPESRC.
 */
static void intel_fbc_get_plane_source_size(const struct intel_fbc_state_cache *cache,
                                            int *width, int *height)
{
        if (width)
                *width = cache->plane.src_w;
        if (height)
                *height = cache->plane.src_h;
}

static int intel_fbc_calculate_cfb_size(struct drm_i915_private *dev_priv,
                                        const struct intel_fbc_state_cache *cache)
{
        int lines;

        intel_fbc_get_plane_source_size(cache, NULL, &lines);
        if (DISPLAY_VER(dev_priv) == 7)
                lines = min(lines, 2048);
        else if (DISPLAY_VER(dev_priv) >= 8)
                lines = min(lines, 2560);

        /* Hardware needs the full buffer stride, not just the active area. */
        return lines * cache->fb.stride;
}

static void i8xx_fbc_deactivate(struct drm_i915_private *dev_priv)
{
        u32 fbc_ctl;

        /* Disable compression */
        fbc_ctl = intel_de_read(dev_priv, FBC_CONTROL);
        if ((fbc_ctl & FBC_CTL_EN) == 0)
                return;

        fbc_ctl &= ~FBC_CTL_EN;
        intel_de_write(dev_priv, FBC_CONTROL, fbc_ctl);

        /* Wait for compressing bit to clear */
        if (intel_de_wait_for_clear(dev_priv, FBC_STATUS,
                                    FBC_STAT_COMPRESSING, 10)) {
                drm_dbg_kms(&dev_priv->drm, "FBC idle timed out\n");
                return;
        }
}

static void i8xx_fbc_activate(struct drm_i915_private *dev_priv)
{
        struct intel_fbc_reg_params *params = &dev_priv->fbc.params;
        int cfb_pitch;
        int i;
        u32 fbc_ctl;

        /* Note: fbc.threshold == 1 for i8xx */
        cfb_pitch = params->cfb_size / FBC_LL_SIZE;
        if (params->fb.stride < cfb_pitch)
                cfb_pitch = params->fb.stride;

        /* FBC_CTL wants 32B or 64B units */
        if (DISPLAY_VER(dev_priv) == 2)
                cfb_pitch = (cfb_pitch / 32) - 1;
        else
                cfb_pitch = (cfb_pitch / 64) - 1;

        /* Clear old tags */
        for (i = 0; i < (FBC_LL_SIZE / 32) + 1; i++)
                intel_de_write(dev_priv, FBC_TAG(i), 0);

        if (DISPLAY_VER(dev_priv) == 4) {
                u32 fbc_ctl2;

                /* Set it up... */
                fbc_ctl2 = FBC_CTL_FENCE_DBL | FBC_CTL_IDLE_IMM;
                fbc_ctl2 |= FBC_CTL_PLANE(params->crtc.i9xx_plane);
                if (params->fence_id >= 0)
                        fbc_ctl2 |= FBC_CTL_CPU_FENCE;
                intel_de_write(dev_priv, FBC_CONTROL2, fbc_ctl2);
                intel_de_write(dev_priv, FBC_FENCE_OFF,
                               params->fence_y_offset);
        }

        /* enable it... */
        fbc_ctl = FBC_CTL_INTERVAL(params->interval);
        fbc_ctl |= FBC_CTL_EN | FBC_CTL_PERIODIC;
        if (IS_I945GM(dev_priv))
                fbc_ctl |= FBC_CTL_C3_IDLE; /* 945 needs special SR handling */
        fbc_ctl |= FBC_CTL_STRIDE(cfb_pitch & 0xff);
        if (params->fence_id >= 0)
                fbc_ctl |= FBC_CTL_FENCENO(params->fence_id);
        intel_de_write(dev_priv, FBC_CONTROL, fbc_ctl);
}

static bool i8xx_fbc_is_active(struct drm_i915_private *dev_priv)
{
        return intel_de_read(dev_priv, FBC_CONTROL) & FBC_CTL_EN;
}

static void g4x_fbc_activate(struct drm_i915_private *dev_priv)
{
        struct intel_fbc_reg_params *params = &dev_priv->fbc.params;
        u32 dpfc_ctl;

        dpfc_ctl = DPFC_CTL_PLANE(params->crtc.i9xx_plane) | DPFC_SR_EN;
        if (params->fb.format->cpp[0] == 2)
                dpfc_ctl |= DPFC_CTL_LIMIT_2X;
        else
                dpfc_ctl |= DPFC_CTL_LIMIT_1X;

        if (params->fence_id >= 0) {
                dpfc_ctl |= DPFC_CTL_FENCE_EN | params->fence_id;
                intel_de_write(dev_priv, DPFC_FENCE_YOFF,
                               params->fence_y_offset);
        } else {
                intel_de_write(dev_priv, DPFC_FENCE_YOFF, 0);
        }

        /* enable it... */
        intel_de_write(dev_priv, DPFC_CONTROL, dpfc_ctl | DPFC_CTL_EN);
}

static void g4x_fbc_deactivate(struct drm_i915_private *dev_priv)
{
        u32 dpfc_ctl;

        /* Disable compression */
        dpfc_ctl = intel_de_read(dev_priv, DPFC_CONTROL);
        if (dpfc_ctl & DPFC_CTL_EN) {
                dpfc_ctl &= ~DPFC_CTL_EN;
                intel_de_write(dev_priv, DPFC_CONTROL, dpfc_ctl);
        }
}

static bool g4x_fbc_is_active(struct drm_i915_private *dev_priv)
{
        return intel_de_read(dev_priv, DPFC_CONTROL) & DPFC_CTL_EN;
}

static void i8xx_fbc_recompress(struct drm_i915_private *dev_priv)
{
        struct intel_fbc_reg_params *params = &dev_priv->fbc.params;
        enum i9xx_plane_id i9xx_plane = params->crtc.i9xx_plane;

        spin_lock_irq(&dev_priv->uncore.lock);
        intel_de_write_fw(dev_priv, DSPADDR(i9xx_plane),
                          intel_de_read_fw(dev_priv, DSPADDR(i9xx_plane)));
        spin_unlock_irq(&dev_priv->uncore.lock);
}

static void i965_fbc_recompress(struct drm_i915_private *dev_priv)
{
        struct intel_fbc_reg_params *params = &dev_priv->fbc.params;
        enum i9xx_plane_id i9xx_plane = params->crtc.i9xx_plane;

        spin_lock_irq(&dev_priv->uncore.lock);
        intel_de_write_fw(dev_priv, DSPSURF(i9xx_plane),
                          intel_de_read_fw(dev_priv, DSPSURF(i9xx_plane)));
        spin_unlock_irq(&dev_priv->uncore.lock);
}

/* This function forces a CFB recompression through the nuke operation. */
static void snb_fbc_recompress(struct drm_i915_private *dev_priv)
{
        struct intel_fbc *fbc = &dev_priv->fbc;

        trace_intel_fbc_nuke(fbc->crtc);

        intel_de_write(dev_priv, MSG_FBC_REND_STATE, FBC_REND_NUKE);
        intel_de_posting_read(dev_priv, MSG_FBC_REND_STATE);
}

static void intel_fbc_recompress(struct drm_i915_private *dev_priv)
{
        if (DISPLAY_VER(dev_priv) >= 6)
                snb_fbc_recompress(dev_priv);
        else if (DISPLAY_VER(dev_priv) >= 4)
                i965_fbc_recompress(dev_priv);
        else
                i8xx_fbc_recompress(dev_priv);
}

static void ilk_fbc_activate(struct drm_i915_private *dev_priv)
{
        struct intel_fbc_reg_params *params = &dev_priv->fbc.params;
        u32 dpfc_ctl;
        int threshold = dev_priv->fbc.threshold;

        dpfc_ctl = DPFC_CTL_PLANE(params->crtc.i9xx_plane);
        if (params->fb.format->cpp[0] == 2)
                threshold++;

        switch (threshold) {
        case 4:
        case 3:
                dpfc_ctl |= DPFC_CTL_LIMIT_4X;
                break;
        case 2:
                dpfc_ctl |= DPFC_CTL_LIMIT_2X;
                break;
        case 1:
                dpfc_ctl |= DPFC_CTL_LIMIT_1X;
                break;
        }

        if (params->fence_id >= 0) {
                dpfc_ctl |= DPFC_CTL_FENCE_EN;
                if (IS_IRONLAKE(dev_priv))
                        dpfc_ctl |= params->fence_id;
                if (IS_SANDYBRIDGE(dev_priv)) {
                        intel_de_write(dev_priv, SNB_DPFC_CTL_SA,
                                       SNB_CPU_FENCE_ENABLE | params->fence_id);
                        intel_de_write(dev_priv, DPFC_CPU_FENCE_OFFSET,
                                       params->fence_y_offset);
                }
        } else {
                if (IS_SANDYBRIDGE(dev_priv)) {
                        intel_de_write(dev_priv, SNB_DPFC_CTL_SA, 0);
                        intel_de_write(dev_priv, DPFC_CPU_FENCE_OFFSET, 0);
                }
        }

        intel_de_write(dev_priv, ILK_DPFC_FENCE_YOFF,
                       params->fence_y_offset);
        /* enable it... */
        intel_de_write(dev_priv, ILK_DPFC_CONTROL, dpfc_ctl | DPFC_CTL_EN);

        intel_fbc_recompress(dev_priv);
}

static void ilk_fbc_deactivate(struct drm_i915_private *dev_priv)
{
        u32 dpfc_ctl;

        /* Disable compression */
        dpfc_ctl = intel_de_read(dev_priv, ILK_DPFC_CONTROL);
        if (dpfc_ctl & DPFC_CTL_EN) {
                dpfc_ctl &= ~DPFC_CTL_EN;
                intel_de_write(dev_priv, ILK_DPFC_CONTROL, dpfc_ctl);
        }
}

static bool ilk_fbc_is_active(struct drm_i915_private *dev_priv)
{
        return intel_de_read(dev_priv, ILK_DPFC_CONTROL) & DPFC_CTL_EN;
}

static void gen7_fbc_activate(struct drm_i915_private *dev_priv)
{
        struct intel_fbc_reg_params *params = &dev_priv->fbc.params;
        u32 dpfc_ctl;
        int threshold = dev_priv->fbc.threshold;

        /* Display WA #0529: skl, kbl, bxt. */
        if (DISPLAY_VER(dev_priv) == 9) {
                u32 val = intel_de_read(dev_priv, CHICKEN_MISC_4);

                val &= ~(FBC_STRIDE_OVERRIDE | FBC_STRIDE_MASK);

                if (params->gen9_wa_cfb_stride)
                        val |= FBC_STRIDE_OVERRIDE | params->gen9_wa_cfb_stride;

                intel_de_write(dev_priv, CHICKEN_MISC_4, val);
        }

        dpfc_ctl = 0;
        if (IS_IVYBRIDGE(dev_priv))
                dpfc_ctl |= IVB_DPFC_CTL_PLANE(params->crtc.i9xx_plane);

        if (params->fb.format->cpp[0] == 2)
                threshold++;

        switch (threshold) {
        case 4:
        case 3:
                dpfc_ctl |= DPFC_CTL_LIMIT_4X;
                break;
        case 2:
                dpfc_ctl |= DPFC_CTL_LIMIT_2X;
                break;
        case 1:
                dpfc_ctl |= DPFC_CTL_LIMIT_1X;
                break;
        }

        if (params->fence_id >= 0) {
                dpfc_ctl |= IVB_DPFC_CTL_FENCE_EN;
                intel_de_write(dev_priv, SNB_DPFC_CTL_SA,
                               SNB_CPU_FENCE_ENABLE | params->fence_id);
                intel_de_write(dev_priv, DPFC_CPU_FENCE_OFFSET,
                               params->fence_y_offset);
        } else if (dev_priv->ggtt.num_fences) {
                intel_de_write(dev_priv, SNB_DPFC_CTL_SA, 0);
                intel_de_write(dev_priv, DPFC_CPU_FENCE_OFFSET, 0);
        }

        if (dev_priv->fbc.false_color)
                dpfc_ctl |= FBC_CTL_FALSE_COLOR;

        intel_de_write(dev_priv, ILK_DPFC_CONTROL, dpfc_ctl | DPFC_CTL_EN);

        intel_fbc_recompress(dev_priv);
}

static bool intel_fbc_hw_is_active(struct drm_i915_private *dev_priv)
{
        if (DISPLAY_VER(dev_priv) >= 5)
                return ilk_fbc_is_active(dev_priv);
        else if (IS_GM45(dev_priv))
                return g4x_fbc_is_active(dev_priv);
        else
                return i8xx_fbc_is_active(dev_priv);
}

static void intel_fbc_hw_activate(struct drm_i915_private *dev_priv)
{
        struct intel_fbc *fbc = &dev_priv->fbc;

        trace_intel_fbc_activate(fbc->crtc);

        fbc->active = true;
        fbc->activated = true;

        if (DISPLAY_VER(dev_priv) >= 7)
                gen7_fbc_activate(dev_priv);
        else if (DISPLAY_VER(dev_priv) >= 5)
                ilk_fbc_activate(dev_priv);
        else if (IS_GM45(dev_priv))
                g4x_fbc_activate(dev_priv);
        else
                i8xx_fbc_activate(dev_priv);
}

static void intel_fbc_hw_deactivate(struct drm_i915_private *dev_priv)
{
        struct intel_fbc *fbc = &dev_priv->fbc;

        trace_intel_fbc_deactivate(fbc->crtc);

        fbc->active = false;

        if (DISPLAY_VER(dev_priv) >= 5)
                ilk_fbc_deactivate(dev_priv);
        else if (IS_GM45(dev_priv))
                g4x_fbc_deactivate(dev_priv);
        else
                i8xx_fbc_deactivate(dev_priv);
}

/**
 * intel_fbc_is_active - Is FBC active?
 * @dev_priv: i915 device instance
 *
 * This function is used to verify the current state of FBC.
 *
 * FIXME: This should be tracked in the plane config eventually
 * instead of queried at runtime for most callers.
 */
bool intel_fbc_is_active(struct drm_i915_private *dev_priv)
{
        return dev_priv->fbc.active;
}

static void intel_fbc_deactivate(struct drm_i915_private *dev_priv,
                                 const char *reason)
{
        struct intel_fbc *fbc = &dev_priv->fbc;

        drm_WARN_ON(&dev_priv->drm, !mutex_is_locked(&fbc->lock));

        if (fbc->active)
                intel_fbc_hw_deactivate(dev_priv);

        fbc->no_fbc_reason = reason;
}

static u64 intel_fbc_cfb_base_max(struct drm_i915_private *i915)
{
        if (DISPLAY_VER(i915) >= 5 || IS_G4X(i915))
                return BIT_ULL(28);
        else
                return BIT_ULL(32);
}

static int find_compression_threshold(struct drm_i915_private *dev_priv,
                                      struct drm_mm_node *node,
                                      unsigned int size,
                                      unsigned int fb_cpp)
{
        int compression_threshold = 1;
        int ret;
        u64 end;

        /* The FBC hardware for BDW/SKL doesn't have access to the stolen
         * reserved range size, so it always assumes the maximum (8mb) is used.
         * If we enable FBC using a CFB on that memory range we'll get FIFO
         * underruns, even if that range is not reserved by the BIOS. */
        if (IS_BROADWELL(dev_priv) || (DISPLAY_VER(dev_priv) == 9 &&
                                       !IS_BROXTON(dev_priv)))
                end = resource_size(&dev_priv->dsm) - 8 * 1024 * 1024;
        else
                end = U64_MAX;

        end = min(end, intel_fbc_cfb_base_max(dev_priv));

        /* HACK: This code depends on what we will do in *_enable_fbc. If that
         * code changes, this code needs to change as well.
         *
         * The enable_fbc code will attempt to use one of our 2 compression
         * thresholds, therefore, in that case, we only have 1 resort.
         */

        /* Try to over-allocate to reduce reallocations and fragmentation. */
        ret = i915_gem_stolen_insert_node_in_range(dev_priv, node, size <<= 1,
                                                   4096, 0, end);
        if (ret == 0)
                return compression_threshold;

again:
        /* HW's ability to limit the CFB is 1:4 */
        if (compression_threshold > 4 ||
            (fb_cpp == 2 && compression_threshold == 2))
                return 0;

        ret = i915_gem_stolen_insert_node_in_range(dev_priv, node, size >>= 1,
                                                   4096, 0, end);
        if (ret && DISPLAY_VER(dev_priv) <= 4) {
                return 0;
        } else if (ret) {
                compression_threshold <<= 1;
                goto again;
        } else {
                return compression_threshold;
        }
}

static int intel_fbc_alloc_cfb(struct drm_i915_private *dev_priv,
                               unsigned int size, unsigned int fb_cpp)
{
        struct intel_fbc *fbc = &dev_priv->fbc;
        struct drm_mm_node *compressed_llb;
        int ret;

        drm_WARN_ON(&dev_priv->drm,
                    drm_mm_node_allocated(&fbc->compressed_fb));

        ret = find_compression_threshold(dev_priv, &fbc->compressed_fb,
                                         size, fb_cpp);
        if (!ret)
                goto err_llb;
        else if (ret > 1) {
                drm_info_once(&dev_priv->drm,
                              "Reducing the compressed framebuffer size. This may lead to less power savings than a non-reduced-size. Try to increase stolen memory size if available in BIOS.\n");
        }

        fbc->threshold = ret;

        if (DISPLAY_VER(dev_priv) >= 5)
                intel_de_write(dev_priv, ILK_DPFC_CB_BASE,
                               fbc->compressed_fb.start);
        else if (IS_GM45(dev_priv)) {
                intel_de_write(dev_priv, DPFC_CB_BASE,
                               fbc->compressed_fb.start);
        } else {
                compressed_llb = kzalloc(sizeof(*compressed_llb), GFP_KERNEL);
                if (!compressed_llb)
                        goto err_fb;

                ret = i915_gem_stolen_insert_node(dev_priv, compressed_llb,
                                                  4096, 4096);
                if (ret)
                        goto err_fb;

                fbc->compressed_llb = compressed_llb;

                GEM_BUG_ON(range_overflows_end_t(u64, dev_priv->dsm.start,
                                                 fbc->compressed_fb.start,
                                                 U32_MAX));
                GEM_BUG_ON(range_overflows_end_t(u64, dev_priv->dsm.start,
                                                 fbc->compressed_llb->start,
                                                 U32_MAX));
                intel_de_write(dev_priv, FBC_CFB_BASE,
                               dev_priv->dsm.start + fbc->compressed_fb.start);
                intel_de_write(dev_priv, FBC_LL_BASE,
                               dev_priv->dsm.start + compressed_llb->start);
        }

        drm_dbg_kms(&dev_priv->drm,
                    "reserved %llu bytes of contiguous stolen space for FBC, threshold: %d\n",
                    fbc->compressed_fb.size, fbc->threshold);

        return 0;

err_fb:
        kfree(compressed_llb);
        i915_gem_stolen_remove_node(dev_priv, &fbc->compressed_fb);
err_llb:
        if (drm_mm_initialized(&dev_priv->mm.stolen))
                drm_info_once(&dev_priv->drm, "not enough stolen space for compressed buffer (need %d more bytes), disabling. Hint: you may be able to increase stolen memory size in the BIOS to avoid this.\n", size);
        return -ENOSPC;
}

static void __intel_fbc_cleanup_cfb(struct drm_i915_private *dev_priv)
{
        struct intel_fbc *fbc = &dev_priv->fbc;

        if (WARN_ON(intel_fbc_hw_is_active(dev_priv)))
                return;

        if (!drm_mm_node_allocated(&fbc->compressed_fb))
                return;

        if (fbc->compressed_llb) {
                i915_gem_stolen_remove_node(dev_priv, fbc->compressed_llb);
                kfree(fbc->compressed_llb);
        }

        i915_gem_stolen_remove_node(dev_priv, &fbc->compressed_fb);
}

void intel_fbc_cleanup_cfb(struct drm_i915_private *dev_priv)
{
        struct intel_fbc *fbc = &dev_priv->fbc;

        if (!HAS_FBC(dev_priv))
                return;

        mutex_lock(&fbc->lock);
        __intel_fbc_cleanup_cfb(dev_priv);
        mutex_unlock(&fbc->lock);
}

static bool stride_is_valid(struct drm_i915_private *dev_priv,
                            u64 modifier, unsigned int stride)
{
        /* This should have been caught earlier. */
        if (drm_WARN_ON_ONCE(&dev_priv->drm, (stride & (64 - 1)) != 0))
                return false;

        /* Below are the additional FBC restrictions. */
        if (stride < 512)
                return false;

        if (DISPLAY_VER(dev_priv) == 2 || DISPLAY_VER(dev_priv) == 3)
                return stride == 4096 || stride == 8192;

        if (DISPLAY_VER(dev_priv) == 4 && !IS_G4X(dev_priv) && stride < 2048)
                return false;

        /* Display WA #1105: skl,bxt,kbl,cfl,glk */
        if ((DISPLAY_VER(dev_priv) == 9 || IS_GEMINILAKE(dev_priv)) &&
            modifier == DRM_FORMAT_MOD_LINEAR && stride & 511)
                return false;

        if (stride > 16384)
                return false;

        return true;
}

static bool pixel_format_is_valid(struct drm_i915_private *dev_priv,
                                  u32 pixel_format)
{
        switch (pixel_format) {
        case DRM_FORMAT_XRGB8888:
        case DRM_FORMAT_XBGR8888:
                return true;
        case DRM_FORMAT_XRGB1555:
        case DRM_FORMAT_RGB565:
                /* 16bpp not supported on gen2 */
                if (DISPLAY_VER(dev_priv) == 2)
                        return false;
                /* WaFbcOnly1to1Ratio:ctg */
                if (IS_G4X(dev_priv))
                        return false;
                return true;
        default:
                return false;
        }
}

static bool rotation_is_valid(struct drm_i915_private *dev_priv,
                              u32 pixel_format, unsigned int rotation)
{
        if (DISPLAY_VER(dev_priv) >= 9 && pixel_format == DRM_FORMAT_RGB565 &&
            drm_rotation_90_or_270(rotation))
                return false;
        else if (DISPLAY_VER(dev_priv) <= 4 && !IS_G4X(dev_priv) &&
                 rotation != DRM_MODE_ROTATE_0)
                return false;

        return true;
}

/*
 * For some reason, the hardware tracking starts looking at whatever we
 * programmed as the display plane base address register. It does not look at
 * the X and Y offset registers. That's why we include the src x/y offsets
 * instead of just looking at the plane size.
 */
static bool intel_fbc_hw_tracking_covers_screen(struct intel_crtc *crtc)
{
        struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
        struct intel_fbc *fbc = &dev_priv->fbc;
        unsigned int effective_w, effective_h, max_w, max_h;

        if (DISPLAY_VER(dev_priv) >= 10) {
                max_w = 5120;
                max_h = 4096;
        } else if (DISPLAY_VER(dev_priv) >= 8 || IS_HASWELL(dev_priv)) {
                max_w = 4096;
                max_h = 4096;
        } else if (IS_G4X(dev_priv) || DISPLAY_VER(dev_priv) >= 5) {
                max_w = 4096;
                max_h = 2048;
        } else {
                max_w = 2048;
                max_h = 1536;
        }

        intel_fbc_get_plane_source_size(&fbc->state_cache, &effective_w,
                                        &effective_h);
        effective_w += fbc->state_cache.plane.adjusted_x;
        effective_h += fbc->state_cache.plane.adjusted_y;

        return effective_w <= max_w && effective_h <= max_h;
}

static bool tiling_is_valid(struct drm_i915_private *dev_priv,
                            u64 modifier)
{
        switch (modifier) {
        case DRM_FORMAT_MOD_LINEAR:
                if (DISPLAY_VER(dev_priv) >= 9)
                        return true;
                return false;
        case I915_FORMAT_MOD_X_TILED:
        case I915_FORMAT_MOD_Y_TILED:
                return true;
        default:
                return false;
        }
}

static void intel_fbc_update_state_cache(struct intel_crtc *crtc,
                                         const struct intel_crtc_state *crtc_state,
                                         const struct intel_plane_state *plane_state)
{
        struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
        struct intel_fbc *fbc = &dev_priv->fbc;
        struct intel_fbc_state_cache *cache = &fbc->state_cache;
        struct drm_framebuffer *fb = plane_state->hw.fb;

        cache->plane.visible = plane_state->uapi.visible;
        if (!cache->plane.visible)
                return;

        cache->crtc.mode_flags = crtc_state->hw.adjusted_mode.flags;
        if (IS_HASWELL(dev_priv) || IS_BROADWELL(dev_priv))
                cache->crtc.hsw_bdw_pixel_rate = crtc_state->pixel_rate;

        cache->plane.rotation = plane_state->hw.rotation;
        /*
         * Src coordinates are already rotated by 270 degrees for
         * the 90/270 degree plane rotation cases (to match the
         * GTT mapping), hence no need to account for rotation here.
         */
        cache->plane.src_w = drm_rect_width(&plane_state->uapi.src) >> 16;
        cache->plane.src_h = drm_rect_height(&plane_state->uapi.src) >> 16;
        cache->plane.adjusted_x = plane_state->view.color_plane[0].x;
        cache->plane.adjusted_y = plane_state->view.color_plane[0].y;

        cache->plane.pixel_blend_mode = plane_state->hw.pixel_blend_mode;

        cache->fb.format = fb->format;
        cache->fb.modifier = fb->modifier;

        /* FIXME is this correct? */
        cache->fb.stride = plane_state->view.color_plane[0].mapping_stride;
        if (drm_rotation_90_or_270(plane_state->hw.rotation))
                cache->fb.stride *= fb->format->cpp[0];

        /* FBC1 compression interval: arbitrary choice of 1 second */
        cache->interval = drm_mode_vrefresh(&crtc_state->hw.adjusted_mode);

        cache->fence_y_offset = intel_plane_fence_y_offset(plane_state);

        drm_WARN_ON(&dev_priv->drm, plane_state->flags & PLANE_HAS_FENCE &&
                    !plane_state->ggtt_vma->fence);

        if (plane_state->flags & PLANE_HAS_FENCE &&
            plane_state->ggtt_vma->fence)
                cache->fence_id = plane_state->ggtt_vma->fence->id;
        else
                cache->fence_id = -1;

        cache->psr2_active = crtc_state->has_psr2;
}

static bool intel_fbc_cfb_size_changed(struct drm_i915_private *dev_priv)
{
        struct intel_fbc *fbc = &dev_priv->fbc;

        return intel_fbc_calculate_cfb_size(dev_priv, &fbc->state_cache) >
                fbc->compressed_fb.size * fbc->threshold;
}

static u16 intel_fbc_gen9_wa_cfb_stride(struct drm_i915_private *dev_priv)
{
        struct intel_fbc *fbc = &dev_priv->fbc;
        struct intel_fbc_state_cache *cache = &fbc->state_cache;

        if ((DISPLAY_VER(dev_priv) == 9) &&
            cache->fb.modifier != I915_FORMAT_MOD_X_TILED)
                return DIV_ROUND_UP(cache->plane.src_w, 32 * fbc->threshold) * 8;
        else
                return 0;
}

static bool intel_fbc_gen9_wa_cfb_stride_changed(struct drm_i915_private *dev_priv)
{
        struct intel_fbc *fbc = &dev_priv->fbc;

        return fbc->params.gen9_wa_cfb_stride != intel_fbc_gen9_wa_cfb_stride(dev_priv);
}

static bool intel_fbc_can_enable(struct drm_i915_private *dev_priv)
{
        struct intel_fbc *fbc = &dev_priv->fbc;

        if (intel_vgpu_active(dev_priv)) {
                fbc->no_fbc_reason = "VGPU is active";
                return false;
        }

        if (!dev_priv->params.enable_fbc) {
                fbc->no_fbc_reason = "disabled per module param or by default";
                return false;
        }

        if (fbc->underrun_detected) {
                fbc->no_fbc_reason = "underrun detected";
                return false;
        }

        return true;
}

static bool intel_fbc_can_activate(struct intel_crtc *crtc)
{
        struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
        struct intel_fbc *fbc = &dev_priv->fbc;
        struct intel_fbc_state_cache *cache = &fbc->state_cache;

        if (!intel_fbc_can_enable(dev_priv))
                return false;

        if (!cache->plane.visible) {
                fbc->no_fbc_reason = "primary plane not visible";
                return false;
        }

        /* We don't need to use a state cache here since this information is
         * global for all CRTC.
         */
        if (fbc->underrun_detected) {
                fbc->no_fbc_reason = "underrun detected";
                return false;
        }

        if (cache->crtc.mode_flags & DRM_MODE_FLAG_INTERLACE) {
                fbc->no_fbc_reason = "incompatible mode";
                return false;
        }

        if (!intel_fbc_hw_tracking_covers_screen(crtc)) {
                fbc->no_fbc_reason = "mode too large for compression";
                return false;
        }

        /* The use of a CPU fence is one of two ways to detect writes by the
         * CPU to the scanout and trigger updates to the FBC.
         *
         * The other method is by software tracking (see
         * intel_fbc_invalidate/flush()), it will manually notify FBC and nuke
         * the current compressed buffer and recompress it.
         *
         * Note that is possible for a tiled surface to be unmappable (and
         * so have no fence associated with it) due to aperture constraints
         * at the time of pinning.
         *
         * FIXME with 90/270 degree rotation we should use the fence on
         * the normal GTT view (the rotated view doesn't even have a
         * fence). Would need changes to the FBC fence Y offset as well.
         * For now this will effectively disable FBC with 90/270 degree
         * rotation.
         */
        if (DISPLAY_VER(dev_priv) < 9 && cache->fence_id < 0) {
                fbc->no_fbc_reason = "framebuffer not tiled or fenced";
                return false;
        }

        if (!pixel_format_is_valid(dev_priv, cache->fb.format->format)) {
                fbc->no_fbc_reason = "pixel format is invalid";
                return false;
        }

        if (!rotation_is_valid(dev_priv, cache->fb.format->format,
                               cache->plane.rotation)) {
                fbc->no_fbc_reason = "rotation unsupported";
                return false;
        }

        if (!tiling_is_valid(dev_priv, cache->fb.modifier)) {
                fbc->no_fbc_reason = "tiling unsupported";
                return false;
        }

        if (!stride_is_valid(dev_priv, cache->fb.modifier, cache->fb.stride)) {
                fbc->no_fbc_reason = "framebuffer stride not supported";
                return false;
        }

        if (cache->plane.pixel_blend_mode != DRM_MODE_BLEND_PIXEL_NONE &&
            cache->fb.format->has_alpha) {
                fbc->no_fbc_reason = "per-pixel alpha blending is incompatible with FBC";
                return false;
        }

        /* WaFbcExceedCdClockThreshold:hsw,bdw */
        if ((IS_HASWELL(dev_priv) || IS_BROADWELL(dev_priv)) &&
            cache->crtc.hsw_bdw_pixel_rate >= dev_priv->cdclk.hw.cdclk * 95 / 100) {
                fbc->no_fbc_reason = "pixel rate is too big";
                return false;
        }

        /* It is possible for the required CFB size change without a
         * crtc->disable + crtc->enable since it is possible to change the
         * stride without triggering a full modeset. Since we try to
         * over-allocate the CFB, there's a chance we may keep FBC enabled even
         * if this happens, but if we exceed the current CFB size we'll have to
         * disable FBC. Notice that it would be possible to disable FBC, wait
         * for a frame, free the stolen node, then try to reenable FBC in case
         * we didn't get any invalidate/deactivate calls, but this would require
         * a lot of tracking just for a specific case. If we conclude it's an
         * important case, we can implement it later. */
        if (intel_fbc_cfb_size_changed(dev_priv)) {
                fbc->no_fbc_reason = "CFB requirements changed";
                return false;
        }

        /*
         * Work around a problem on GEN9+ HW, where enabling FBC on a plane
         * having a Y offset that isn't divisible by 4 causes FIFO underrun
         * and screen flicker.
         */
        if (DISPLAY_VER(dev_priv) >= 9 &&
            (fbc->state_cache.plane.adjusted_y & 3)) {
                fbc->no_fbc_reason = "plane Y offset is misaligned";
                return false;
        }

        /* Wa_22010751166: icl, ehl, tgl, dg1, rkl */
        if (DISPLAY_VER(dev_priv) >= 11 &&
            (cache->plane.src_h + cache->plane.adjusted_y) % 4) {
                fbc->no_fbc_reason = "plane height + offset is non-modulo of 4";
                return false;
        }

        /*
         * Tigerlake is not supporting FBC with PSR2.
         * Recommendation is to keep this combination disabled
         * Bspec: 50422 HSD: 14010260002
         */
        if (fbc->state_cache.psr2_active && IS_TIGERLAKE(dev_priv)) {
                fbc->no_fbc_reason = "not supported with PSR2";
                return false;
        }

        return true;
}

static void intel_fbc_get_reg_params(struct intel_crtc *crtc,
                                     struct intel_fbc_reg_params *params)
{
        struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
        struct intel_fbc *fbc = &dev_priv->fbc;
        struct intel_fbc_state_cache *cache = &fbc->state_cache;

        /* Since all our fields are integer types, use memset here so the
         * comparison function can rely on memcmp because the padding will be
         * zero. */
        memset(params, 0, sizeof(*params));

        params->fence_id = cache->fence_id;
        params->fence_y_offset = cache->fence_y_offset;

        params->interval = cache->interval;

        params->crtc.pipe = crtc->pipe;
        params->crtc.i9xx_plane = to_intel_plane(crtc->base.primary)->i9xx_plane;

        params->fb.format = cache->fb.format;
        params->fb.modifier = cache->fb.modifier;
        params->fb.stride = cache->fb.stride;

        params->cfb_size = intel_fbc_calculate_cfb_size(dev_priv, cache);

        params->gen9_wa_cfb_stride = cache->gen9_wa_cfb_stride;

        params->plane_visible = cache->plane.visible;
}

static bool intel_fbc_can_flip_nuke(const struct intel_crtc_state *crtc_state)
{
        struct intel_crtc *crtc = to_intel_crtc(crtc_state->uapi.crtc);
        struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
        const struct intel_fbc *fbc = &dev_priv->fbc;
        const struct intel_fbc_state_cache *cache = &fbc->state_cache;
        const struct intel_fbc_reg_params *params = &fbc->params;

        if (drm_atomic_crtc_needs_modeset(&crtc_state->uapi))
                return false;

        if (!params->plane_visible)
                return false;

        if (!intel_fbc_can_activate(crtc))
                return false;

        if (params->fb.format != cache->fb.format)
                return false;

        if (params->fb.modifier != cache->fb.modifier)
                return false;

        if (params->fb.stride != cache->fb.stride)
                return false;

        if (params->cfb_size != intel_fbc_calculate_cfb_size(dev_priv, cache))
                return false;

        if (params->gen9_wa_cfb_stride != cache->gen9_wa_cfb_stride)
                return false;

        return true;
}

bool intel_fbc_pre_update(struct intel_atomic_state *state,

                          struct intel_crtc *crtc)
{
        struct intel_plane *plane = to_intel_plane(crtc->base.primary);
        const struct intel_crtc_state *crtc_state =
                intel_atomic_get_new_crtc_state(state, crtc);
        const struct intel_plane_state *plane_state =
                intel_atomic_get_new_plane_state(state, plane);
        struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
        struct intel_fbc *fbc = &dev_priv->fbc;
        const char *reason = "update pending";
        bool need_vblank_wait = false;

        if (!plane->has_fbc || !plane_state)
                return need_vblank_wait;

        mutex_lock(&fbc->lock);

        if (fbc->crtc != crtc)
                goto unlock;

        intel_fbc_update_state_cache(crtc, crtc_state, plane_state);
        fbc->flip_pending = true;

        if (!intel_fbc_can_flip_nuke(crtc_state)) {
                intel_fbc_deactivate(dev_priv, reason);

                /*
                 * Display WA #1198: glk+
                 * Need an extra vblank wait between FBC disable and most plane
                 * updates. Bspec says this is only needed for plane disable, but
                 * that is not true. Touching most plane registers will cause the
                 * corruption to appear. Also SKL/derivatives do not seem to be
                 * affected.
                 *
                 * TODO: could optimize this a bit by sampling the frame
                 * counter when we disable FBC (if it was already done earlier)
                 * and skipping the extra vblank wait before the plane update
                 * if at least one frame has already passed.
                 */
                if (fbc->activated &&
                    DISPLAY_VER(dev_priv) >= 10)
                        need_vblank_wait = true;
                fbc->activated = false;
        }
unlock:
        mutex_unlock(&fbc->lock);

        return need_vblank_wait;
}

/**
 * __intel_fbc_disable - disable FBC
 * @dev_priv: i915 device instance
 *
 * This is the low level function that actually disables FBC. Callers should
 * grab the FBC lock.
 */
static void __intel_fbc_disable(struct drm_i915_private *dev_priv)
{
        struct intel_fbc *fbc = &dev_priv->fbc;
        struct intel_crtc *crtc = fbc->crtc;

        drm_WARN_ON(&dev_priv->drm, !mutex_is_locked(&fbc->lock));
        drm_WARN_ON(&dev_priv->drm, !fbc->crtc);
        drm_WARN_ON(&dev_priv->drm, fbc->active);

        drm_dbg_kms(&dev_priv->drm, "Disabling FBC on pipe %c\n",
                    pipe_name(crtc->pipe));

        __intel_fbc_cleanup_cfb(dev_priv);

        fbc->crtc = NULL;
}

static void __intel_fbc_post_update(struct intel_crtc *crtc)
{
        struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
        struct intel_fbc *fbc = &dev_priv->fbc;

        drm_WARN_ON(&dev_priv->drm, !mutex_is_locked(&fbc->lock));

        if (fbc->crtc != crtc)
                return;

        fbc->flip_pending = false;

        if (!dev_priv->params.enable_fbc) {
                intel_fbc_deactivate(dev_priv, "disabled at runtime per module param");
                __intel_fbc_disable(dev_priv);

                return;
        }

        intel_fbc_get_reg_params(crtc, &fbc->params);

        if (!intel_fbc_can_activate(crtc))
                return;

        if (!fbc->busy_bits)
                intel_fbc_hw_activate(dev_priv);
        else
                intel_fbc_deactivate(dev_priv, "frontbuffer write");
}

void intel_fbc_post_update(struct intel_atomic_state *state,
                           struct intel_crtc *crtc)
{
        struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
        struct intel_plane *plane = to_intel_plane(crtc->base.primary);
        const struct intel_plane_state *plane_state =
                intel_atomic_get_new_plane_state(state, plane);
        struct intel_fbc *fbc = &dev_priv->fbc;

        if (!plane->has_fbc || !plane_state)
                return;

        mutex_lock(&fbc->lock);
        __intel_fbc_post_update(crtc);
        mutex_unlock(&fbc->lock);
}

static unsigned int intel_fbc_get_frontbuffer_bit(struct intel_fbc *fbc)
{
        if (fbc->crtc)
                return to_intel_plane(fbc->crtc->base.primary)->frontbuffer_bit;
        else
                return fbc->possible_framebuffer_bits;
}

void intel_fbc_invalidate(struct drm_i915_private *dev_priv,
                          unsigned int frontbuffer_bits,
                          enum fb_op_origin origin)
{
        struct intel_fbc *fbc = &dev_priv->fbc;

        if (!HAS_FBC(dev_priv))
                return;

        if (origin == ORIGIN_GTT || origin == ORIGIN_FLIP || origin == ORIGIN_CURSOR_UPDATE)
                return;

        mutex_lock(&fbc->lock);

        fbc->busy_bits |= intel_fbc_get_frontbuffer_bit(fbc) & frontbuffer_bits;

        if (fbc->crtc && fbc->busy_bits)
                intel_fbc_deactivate(dev_priv, "frontbuffer write");

        mutex_unlock(&fbc->lock);
}

void intel_fbc_flush(struct drm_i915_private *dev_priv,
                     unsigned int frontbuffer_bits, enum fb_op_origin origin)
{
        struct intel_fbc *fbc = &dev_priv->fbc;

        if (!HAS_FBC(dev_priv))
                return;

        /*
         * GTT tracking does not nuke the entire cfb
         * so don't clear busy_bits set for some other
         * reason.
         */
        if (origin == ORIGIN_GTT)
                return;

        mutex_lock(&fbc->lock);

        fbc->busy_bits &= ~frontbuffer_bits;

        if (origin == ORIGIN_FLIP || origin == ORIGIN_CURSOR_UPDATE)
                goto out;

        if (!fbc->busy_bits && fbc->crtc &&
            (frontbuffer_bits & intel_fbc_get_frontbuffer_bit(fbc))) {
                if (fbc->active)
                        intel_fbc_recompress(dev_priv);
                else if (!fbc->flip_pending)
                        __intel_fbc_post_update(fbc->crtc);
        }

out:
        mutex_unlock(&fbc->lock);
}

/**
 * intel_fbc_choose_crtc - select a CRTC to enable FBC on
 * @dev_priv: i915 device instance
 * @state: the atomic state structure
 *
 * This function looks at the proposed state for CRTCs and planes, then chooses
 * which pipe is going to have FBC by setting intel_crtc_state->enable_fbc to
 * true.
 *
 * Later, intel_fbc_enable is going to look for state->enable_fbc and then maybe
 * enable FBC for the chosen CRTC. If it does, it will set dev_priv->fbc.crtc.
 */
void intel_fbc_choose_crtc(struct drm_i915_private *dev_priv,
                           struct intel_atomic_state *state)
{
        struct intel_fbc *fbc = &dev_priv->fbc;
        struct intel_plane *plane;
        struct intel_plane_state *plane_state;
        bool crtc_chosen = false;
        int i;

        mutex_lock(&fbc->lock);

        /* Does this atomic commit involve the CRTC currently tied to FBC? */
        if (fbc->crtc &&
            !intel_atomic_get_new_crtc_state(state, fbc->crtc))
                goto out;

        if (!intel_fbc_can_enable(dev_priv))
                goto out;

        /* Simply choose the first CRTC that is compatible and has a visible
         * plane. We could go for fancier schemes such as checking the plane
         * size, but this would just affect the few platforms that don't tie FBC
         * to pipe or plane A. */
        for_each_new_intel_plane_in_state(state, plane, plane_state, i) {
                struct intel_crtc_state *crtc_state;
                struct intel_crtc *crtc = to_intel_crtc(plane_state->hw.crtc);

                if (!plane->has_fbc)
                        continue;

                if (!plane_state->uapi.visible)
                        continue;

                crtc_state = intel_atomic_get_new_crtc_state(state, crtc);

                crtc_state->enable_fbc = true;
                crtc_chosen = true;
                break;
        }

        if (!crtc_chosen)
                fbc->no_fbc_reason = "no suitable CRTC for FBC";

out:
        mutex_unlock(&fbc->lock);
}

/**
 * intel_fbc_enable: tries to enable FBC on the CRTC
 * @crtc: the CRTC
 * @state: corresponding &drm_crtc_state for @crtc
 *
 * This function checks if the given CRTC was chosen for FBC, then enables it if
 * possible. Notice that it doesn't activate FBC. It is valid to call
 * intel_fbc_enable multiple times for the same pipe without an
 * intel_fbc_disable in the middle, as long as it is deactivated.
 */
void intel_fbc_enable(struct intel_atomic_state *state,
                      struct intel_crtc *crtc)
{
        struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
        struct intel_plane *plane = to_intel_plane(crtc->base.primary);
        const struct intel_crtc_state *crtc_state =
                intel_atomic_get_new_crtc_state(state, crtc);
        const struct intel_plane_state *plane_state =
                intel_atomic_get_new_plane_state(state, plane);
        struct intel_fbc *fbc = &dev_priv->fbc;
        struct intel_fbc_state_cache *cache = &fbc->state_cache;

        if (!plane->has_fbc || !plane_state)
                return;

        mutex_lock(&fbc->lock);

        if (fbc->crtc) {
                if (fbc->crtc != crtc ||
                    (!intel_fbc_cfb_size_changed(dev_priv) &&
                     !intel_fbc_gen9_wa_cfb_stride_changed(dev_priv)))
                        goto out;

                __intel_fbc_disable(dev_priv);
        }

        drm_WARN_ON(&dev_priv->drm, fbc->active);

        intel_fbc_update_state_cache(crtc, crtc_state, plane_state);

        /* FIXME crtc_state->enable_fbc lies :( */
        if (!cache->plane.visible)
                goto out;

        if (intel_fbc_alloc_cfb(dev_priv,
                                intel_fbc_calculate_cfb_size(dev_priv, cache),
                                plane_state->hw.fb->format->cpp[0])) {
                cache->plane.visible = false;
                fbc->no_fbc_reason = "not enough stolen memory";
                goto out;
        }

        cache->gen9_wa_cfb_stride = intel_fbc_gen9_wa_cfb_stride(dev_priv);

        drm_dbg_kms(&dev_priv->drm, "Enabling FBC on pipe %c\n",
                    pipe_name(crtc->pipe));
        fbc->no_fbc_reason = "FBC enabled but not active yet\n";

        fbc->crtc = crtc;
out:
        mutex_unlock(&fbc->lock);
}

/**
 * intel_fbc_disable - disable FBC if it's associated with crtc
 * @crtc: the CRTC
 *
 * This function disables FBC if it's associated with the provided CRTC.
 */
void intel_fbc_disable(struct intel_crtc *crtc)
{
        struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
        struct intel_plane *plane = to_intel_plane(crtc->base.primary);
        struct intel_fbc *fbc = &dev_priv->fbc;

        if (!plane->has_fbc)
                return;

        mutex_lock(&fbc->lock);
        if (fbc->crtc == crtc)
                __intel_fbc_disable(dev_priv);
        mutex_unlock(&fbc->lock);
}

/**
 * intel_fbc_global_disable - globally disable FBC
 * @dev_priv: i915 device instance
 *
 * This function disables FBC regardless of which CRTC is associated with it.
 */
void intel_fbc_global_disable(struct drm_i915_private *dev_priv)
{
        struct intel_fbc *fbc = &dev_priv->fbc;

        if (!HAS_FBC(dev_priv))
                return;

        mutex_lock(&fbc->lock);
        if (fbc->crtc) {
                drm_WARN_ON(&dev_priv->drm, fbc->crtc->active);
                __intel_fbc_disable(dev_priv);
        }
        mutex_unlock(&fbc->lock);
}

static void intel_fbc_underrun_work_fn(struct work_struct *work)
{
        struct drm_i915_private *dev_priv =
                container_of(work, struct drm_i915_private, fbc.underrun_work);
        struct intel_fbc *fbc = &dev_priv->fbc;

        mutex_lock(&fbc->lock);

        /* Maybe we were scheduled twice. */
        if (fbc->underrun_detected || !fbc->crtc)
                goto out;

        drm_dbg_kms(&dev_priv->drm, "Disabling FBC due to FIFO underrun.\n");
        fbc->underrun_detected = true;

        intel_fbc_deactivate(dev_priv, "FIFO underrun");
out:
        mutex_unlock(&fbc->lock);
}

/*
 * intel_fbc_reset_underrun - reset FBC fifo underrun status.
 * @dev_priv: i915 device instance
 *
 * See intel_fbc_handle_fifo_underrun_irq(). For automated testing we
 * want to re-enable FBC after an underrun to increase test coverage.
 */
int intel_fbc_reset_underrun(struct drm_i915_private *dev_priv)
{
        int ret;

        cancel_work_sync(&dev_priv->fbc.underrun_work);

        ret = mutex_lock_interruptible(&dev_priv->fbc.lock);
        if (ret)
                return ret;

        if (dev_priv->fbc.underrun_detected) {
                drm_dbg_kms(&dev_priv->drm,
                            "Re-allowing FBC after fifo underrun\n");
                dev_priv->fbc.no_fbc_reason = "FIFO underrun cleared";
        }

        dev_priv->fbc.underrun_detected = false;
        mutex_unlock(&dev_priv->fbc.lock);

        return 0;
}

/**
 * intel_fbc_handle_fifo_underrun_irq - disable FBC when we get a FIFO underrun
 * @dev_priv: i915 device instance
 *
 * Without FBC, most underruns are harmless and don't really cause too many
 * problems, except for an annoying message on dmesg. With FBC, underruns can
 * become black screens or even worse, especially when paired with bad
 * watermarks. So in order for us to be on the safe side, completely disable FBC
 * in case we ever detect a FIFO underrun on any pipe. An underrun on any pipe
 * already suggests that watermarks may be bad, so try to be as safe as
 * possible.
 *
 * This function is called from the IRQ handler.
 */
void intel_fbc_handle_fifo_underrun_irq(struct drm_i915_private *dev_priv)
{
        struct intel_fbc *fbc = &dev_priv->fbc;

        if (!HAS_FBC(dev_priv))
                return;

        /* There's no guarantee that underrun_detected won't be set to true
         * right after this check and before the work is scheduled, but that's
         * not a problem since we'll check it again under the work function
         * while FBC is locked. This check here is just to prevent us from
         * unnecessarily scheduling the work, and it relies on the fact that we
         * never switch underrun_detect back to false after it's true. */
        if (READ_ONCE(fbc->underrun_detected))
                return;

        schedule_work(&fbc->underrun_work);
}

/*
 * The DDX driver changes its behavior depending on the value it reads from
 * i915.enable_fbc, so sanitize it by translating the default value into either
 * 0 or 1 in order to allow it to know what's going on.
 *
 * Notice that this is done at driver initialization and we still allow user
 * space to change the value during runtime without sanitizing it again. IGT
 * relies on being able to change i915.enable_fbc at runtime.
 */
static int intel_sanitize_fbc_option(struct drm_i915_private *dev_priv)
{
        if (dev_priv->params.enable_fbc >= 0)
                return !!dev_priv->params.enable_fbc;

        if (!HAS_FBC(dev_priv))
                return 0;

        if (IS_BROADWELL(dev_priv) || DISPLAY_VER(dev_priv) >= 9)
                return 1;

        return 0;
}

static bool need_fbc_vtd_wa(struct drm_i915_private *dev_priv)
{
        /* WaFbcTurnOffFbcWhenHyperVisorIsUsed:skl,bxt */
        if (intel_vtd_active() &&
            (IS_SKYLAKE(dev_priv) || IS_BROXTON(dev_priv))) {
                drm_info(&dev_priv->drm,
                         "Disabling framebuffer compression (FBC) to prevent screen flicker with VT-d enabled\n");
                return true;
        }

        return false;
}

/**
 * intel_fbc_init - Initialize FBC
 * @dev_priv: the i915 device
 *
 * This function might be called during PM init process.
 */
void intel_fbc_init(struct drm_i915_private *dev_priv)
{
        struct intel_fbc *fbc = &dev_priv->fbc;

        INIT_WORK(&fbc->underrun_work, intel_fbc_underrun_work_fn);
        mutex_init(&fbc->lock);
        fbc->active = false;

        if (!drm_mm_initialized(&dev_priv->mm.stolen))
                mkwrite_device_info(dev_priv)->display.has_fbc = false;

        if (need_fbc_vtd_wa(dev_priv))
                mkwrite_device_info(dev_priv)->display.has_fbc = false;

        dev_priv->params.enable_fbc = intel_sanitize_fbc_option(dev_priv);
        drm_dbg_kms(&dev_priv->drm, "Sanitized enable_fbc value: %d\n",
                    dev_priv->params.enable_fbc);

        if (!HAS_FBC(dev_priv)) {
                fbc->no_fbc_reason = "unsupported by this chipset";
                return;
        }

        /* We still don't have any sort of hardware state readout for FBC, so
         * deactivate it in case the BIOS activated it to make sure software
         * matches the hardware state. */
        if (intel_fbc_hw_is_active(dev_priv))
                intel_fbc_hw_deactivate(dev_priv);
}