[PATCH v2 15/17] drm/i915: Use vblank workers for gamma updates
Ville Syrjala
ville.syrjala at linux.intel.com
Tue Sep 10 16:08:17 UTC 2019
From: Ville Syrjälä <ville.syrjala at linux.intel.com>
The pipe gamma registers are single buffered so they should only
be updated during the vblank to avoid screen tearing. In fact they
really should only be updated between start of vblank and frame
start because that is the only time the pipe is guaranteed to be
empty. Already at frame start the pipe begins to fill up with
data for the next frame.
Unfortunately frame start happens ~1-4 scanlines after the start
of vblank which in practie doesn't always leave us enough time to
finish the gamma update in time (gamma LUTs can be several KiB of
data we have to bash into the registers). However we must try our
best and so we'll add a vblank work for each pipe from where we
can do the gamma update.
Even though the vblank worker is running on a high prority thread
we still have to contend with C-states. If the CPU happens be in
a deep C-state when the vblank interrupt arrives even the irq
handler gets delayed massively (I've observed dozens of scanlines
worth of latency). To avoid that problem we'll use the qos mechanism
to keep the CPU awake while the vblank work is scheduled.
With all this hooked up we can finally to almost atomic gamma
updates. It even works across several pipes from the same atomic
commit which previously was a total fail because we did the
gamma updates for each pipe serially. In practice we still miss
the frame start easily and so ~100 pixels of the new frame
generally make it through with the old gamma. I don't see any
way to avoid that so we'll just have to live with it. Also it's
possible that high system load etc. could still cause us blow
past the end of vblank, but not much we can do there either
except rewrite the scheduler.
In the future the DSB should take over this responsibility
which will hopefully avoid some of these issues.
v2: Add missing intel_atomic_state fwd declaration
v3: Clean up properly when not scheduling the worker
Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
drivers/gpu/drm/i915/display/intel_atomic.c | 3 +
drivers/gpu/drm/i915/display/intel_display.c | 194 ++++++++++++------
drivers/gpu/drm/i915/display/intel_display.h | 11 +
.../drm/i915/display/intel_display_types.h | 6 +
drivers/gpu/drm/i915/display/intel_sprite.c | 56 ++++-
drivers/gpu/drm/i915/display/intel_sprite.h | 4 +-
drivers/gpu/drm/i915/i915_drv.c | 1 +
7 files changed, 211 insertions(+), 64 deletions(-)
diff --git a/drivers/gpu/drm/i915/display/intel_atomic.c b/drivers/gpu/drm/i915/display/intel_atomic.c
index a8ce0e16a2fa..70f82b696336 100644
--- a/drivers/gpu/drm/i915/display/intel_atomic.c
+++ b/drivers/gpu/drm/i915/display/intel_atomic.c
@@ -205,6 +205,9 @@ intel_crtc_duplicate_state(struct drm_crtc *crtc)
crtc_state->fb_bits = 0;
crtc_state->update_planes = 0;
crtc_state->put_domains = 0;
+ crtc_state->state = NULL;
+ drm_vblank_work_init(&crtc_state->vblank_work,
+ crtc, intel_crtc_vblank_work);
return &crtc_state->base;
}
diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
index 34bca50570b7..8dd9cc1107f3 100644
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -11466,6 +11466,7 @@ static void intel_crtc_destroy(struct drm_crtc *crtc)
struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
drm_crtc_cleanup(crtc);
+ pm_qos_remove_request(&intel_crtc->pm_qos);
kfree(intel_crtc);
}
@@ -12278,6 +12279,7 @@ clear_intel_crtc_state(struct intel_crtc_state *crtc_state)
memcpy(saved_state->icl_port_dplls, crtc_state->icl_port_dplls,
sizeof(saved_state->icl_port_dplls));
saved_state->crc_enabled = crtc_state->crc_enabled;
+ saved_state->vblank_work = crtc_state->vblank_work;
if (IS_G4X(dev_priv) ||
IS_VALLEYVIEW(dev_priv) || IS_CHERRYVIEW(dev_priv))
saved_state->wm = crtc_state->wm;
@@ -14025,6 +14027,84 @@ static void intel_atomic_cleanup_work(struct work_struct *work)
intel_atomic_helper_free_state(i915);
}
+static void intel_atomic_commit_done(struct intel_atomic_state *state)
+{
+ struct drm_i915_private *i915 = to_i915(state->base.dev);
+
+ drm_atomic_helper_wait_for_flip_done(&i915->drm, &state->base);
+
+ if (state->modeset)
+ intel_set_cdclk_post_plane_update(i915, &state->cdclk.actual,
+ &i915->cdclk.actual,
+ state->cdclk.pipe);
+
+ if (intel_can_enable_sagv(state))
+ intel_enable_sagv(i915);
+
+ queue_work(system_highpri_wq, &state->base.commit_work);
+}
+
+bool intel_crtc_need_lut_load(const struct intel_crtc_state *crtc_state)
+{
+ return !needs_modeset(crtc_state) &&
+ (crtc_state->base.color_mgmt_changed ||
+ crtc_state->update_pipe);
+}
+
+static void intel_crtc_do_vblank_work(struct intel_atomic_state *state,
+ struct intel_crtc_state *new_crtc_state,
+ u64 count)
+{
+ struct intel_crtc *crtc = to_intel_crtc(new_crtc_state->base.crtc);
+ struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
+ struct intel_crtc_state *old_crtc_state =
+ intel_atomic_get_old_crtc_state(state, crtc);
+
+ if (new_crtc_state->base.active &&
+ intel_crtc_need_lut_load(new_crtc_state))
+ intel_color_load_luts(new_crtc_state);
+
+ /*
+ * Now that the vblank has passed, we can go ahead and program the
+ * optimal watermarks on platforms that need two-step watermark
+ * programming.
+ */
+ if (dev_priv->display.optimize_watermarks)
+ dev_priv->display.optimize_watermarks(state, new_crtc_state);
+
+ intel_post_plane_update(old_crtc_state);
+
+ if (new_crtc_state->put_domains)
+ modeset_put_power_domains(dev_priv, new_crtc_state->put_domains);
+
+ pm_qos_update_request(&dev_priv->pm_qos, PM_QOS_DEFAULT_VALUE);
+}
+
+void intel_crtc_vblank_work(struct drm_vblank_work *work,
+ u64 count)
+{
+ struct intel_crtc_state *new_crtc_state =
+ container_of(work, struct intel_crtc_state, vblank_work);
+ struct intel_atomic_state *state = new_crtc_state->state;
+
+ intel_crtc_do_vblank_work(state, new_crtc_state, count);
+
+ new_crtc_state->state = NULL;
+
+ if (atomic_dec_and_test(&state->cleanup_count))
+ intel_atomic_commit_done(state);
+}
+
+static void intel_atomic_flush_vblank_works(struct intel_atomic_state *state)
+{
+ struct intel_crtc_state *old_crtc_state;
+ struct intel_crtc *crtc;
+ int i;
+
+ for_each_old_intel_crtc_in_state(state, crtc, old_crtc_state, i)
+ drm_vblank_work_flush(&old_crtc_state->vblank_work);
+}
+
static void intel_atomic_commit_tail(struct intel_atomic_state *state)
{
struct drm_device *dev = state->base.dev;
@@ -14034,6 +14114,8 @@ static void intel_atomic_commit_tail(struct intel_atomic_state *state)
intel_wakeref_t wakeref = 0;
int i;
+ intel_atomic_flush_vblank_works(state);
+
intel_atomic_commit_fence_wait(state);
drm_atomic_helper_wait_for_dependencies(&state->base);
@@ -14045,7 +14127,6 @@ static void intel_atomic_commit_tail(struct intel_atomic_state *state)
new_crtc_state, i) {
if (needs_modeset(new_crtc_state) ||
new_crtc_state->update_pipe) {
-
new_crtc_state->put_domains =
modeset_get_crtc_power_domains(new_crtc_state);
}
@@ -14075,6 +14156,17 @@ static void intel_atomic_commit_tail(struct intel_atomic_state *state)
intel_modeset_verify_disabled(dev_priv, state);
}
+ /*
+ * Defer the cleanup of the old state to a separate worker to not
+ * impede the current task (userspace for blocking modesets) that
+ * are executed inline. For out-of-line asynchronous modesets/flips,
+ * deferring to a new worker seems overkill, but we would place a
+ * schedule point (cond_resched()) here anyway to keep latencies
+ * down.
+ */
+ INIT_WORK(&state->base.commit_work, intel_atomic_cleanup_work);
+ atomic_set(&state->cleanup_count, 1);
+
/* Complete the events for pipes that have now been disabled */
for_each_new_intel_crtc_in_state(state, crtc, new_crtc_state, i) {
bool modeset = needs_modeset(new_crtc_state);
@@ -14087,6 +14179,10 @@ static void intel_atomic_commit_tail(struct intel_atomic_state *state)
new_crtc_state->base.event = NULL;
}
+
+ /* FIXME should we do this before or after update_crtcs()? */
+ if (!new_crtc_state->base.active)
+ intel_crtc_do_vblank_work(state, new_crtc_state, 0);
}
if (state->modeset)
@@ -14095,63 +14191,25 @@ static void intel_atomic_commit_tail(struct intel_atomic_state *state)
/* Now enable the clocks, plane, pipe, and connectors that we set up. */
dev_priv->display.commit_modeset_enables(state);
- if (state->modeset) {
+ if (state->modeset)
intel_encoders_update_complete(state);
- intel_set_cdclk_post_plane_update(dev_priv,
- &state->cdclk.actual,
- &dev_priv->cdclk.actual,
- state->cdclk.pipe);
- }
-
- /* FIXME: We should call drm_atomic_helper_commit_hw_done() here
- * already, but still need the state for the delayed optimization. To
- * fix this:
- * - wrap the optimization/post_plane_update stuff into a per-crtc work.
- * - schedule that vblank worker _before_ calling hw_done
- * - at the start of commit_tail, cancel it _synchrously
- * - switch over to the vblank wait helper in the core after that since
- * we don't need out special handling any more.
- */
- drm_atomic_helper_wait_for_flip_done(dev, &state->base);
-
- for_each_new_intel_crtc_in_state(state, crtc, new_crtc_state, i) {
- if (new_crtc_state->base.active &&
- !needs_modeset(new_crtc_state) &&
- (new_crtc_state->base.color_mgmt_changed ||
- new_crtc_state->update_pipe))
- intel_color_load_luts(new_crtc_state);
- }
+ drm_atomic_helper_commit_hw_done(&state->base);
/*
- * Now that the vblank has passed, we can go ahead and program the
- * optimal watermarks on platforms that need two-step watermark
- * programming.
+ * FIXME intel_modeset_verify_crtc() clobbers
+ * old_crtc_state->commit which causes explosions
+ * int the parallel works.
*
- * TODO: Move this (and other cleanup) to an async worker eventually.
+ * FIXME how does this even work in the
+ * pre-vblank work era?
*/
- for_each_new_intel_crtc_in_state(state, crtc, new_crtc_state, i) {
- if (dev_priv->display.optimize_watermarks)
- dev_priv->display.optimize_watermarks(state,
- new_crtc_state);
- }
-
- for_each_oldnew_intel_crtc_in_state(state, crtc, old_crtc_state, new_crtc_state, i) {
- intel_post_plane_update(old_crtc_state);
-
- if (new_crtc_state->put_domains)
- modeset_put_power_domains(dev_priv, new_crtc_state->put_domains);
-
- intel_modeset_verify_crtc(crtc, state, new_crtc_state);
- }
+ if (state->modeset) {
+ for_each_new_intel_crtc_in_state(state, crtc, new_crtc_state, i)
+ intel_modeset_verify_crtc(crtc, state, new_crtc_state);
- if (state->modeset)
intel_verify_planes(state);
-
- if (state->modeset && intel_can_enable_sagv(state))
- intel_enable_sagv(dev_priv);
-
- drm_atomic_helper_commit_hw_done(&state->base);
+ }
if (state->modeset) {
/* As one of the primary mmio accessors, KMS has a high
@@ -14165,16 +14223,8 @@ static void intel_atomic_commit_tail(struct intel_atomic_state *state)
}
intel_runtime_pm_put(&dev_priv->runtime_pm, state->wakeref);
- /*
- * Defer the cleanup of the old state to a separate worker to not
- * impede the current task (userspace for blocking modesets) that
- * are executed inline. For out-of-line asynchronous modesets/flips,
- * deferring to a new worker seems overkill, but we would place a
- * schedule point (cond_resched()) here anyway to keep latencies
- * down.
- */
- INIT_WORK(&state->base.commit_work, intel_atomic_cleanup_work);
- queue_work(system_highpri_wq, &state->base.commit_work);
+ if (atomic_dec_and_test(&state->cleanup_count))
+ intel_atomic_commit_done(state);
}
static void intel_atomic_commit_work(struct work_struct *work)
@@ -14311,6 +14361,7 @@ static int intel_atomic_commit(struct drm_device *dev,
if (state->modeset)
flush_workqueue(dev_priv->modeset_wq);
intel_atomic_commit_tail(state);
+ drm_atomic_helper_wait_for_flip_done(dev, &state->base);
}
return 0;
@@ -14614,6 +14665,15 @@ static void intel_begin_crtc_commit(struct intel_atomic_state *state,
intel_atomic_get_new_crtc_state(state, crtc);
bool modeset = needs_modeset(new_crtc_state);
+ /*
+ * Make sure we wake up as quickly as possible when
+ * irq fires. Otherwise we risk the single buffered
+ * regiser update can get delayed until we're already
+ * in the active portion of the new frame.
+ */
+ if (intel_crtc_need_lut_load(new_crtc_state))
+ pm_qos_update_request(&crtc->pm_qos, 0);
+
/* Perform vblank evasion around commit operation */
intel_pipe_update_start(new_crtc_state);
@@ -14661,13 +14721,17 @@ static void intel_finish_crtc_commit(struct intel_atomic_state *state,
intel_atomic_get_old_crtc_state(state, crtc);
struct intel_crtc_state *new_crtc_state =
intel_atomic_get_new_crtc_state(state, crtc);
+ int ret;
- intel_pipe_update_end(new_crtc_state);
+ ret = intel_pipe_update_end(state, new_crtc_state);
if (new_crtc_state->update_pipe &&
!needs_modeset(new_crtc_state) &&
old_crtc_state->base.mode.private_flags & I915_MODE_FLAG_INHERITED)
intel_crtc_arm_fifo_underrun(crtc, new_crtc_state);
+
+ if (WARN_ON_ONCE(ret < 0) || ret != 0)
+ intel_crtc_do_vblank_work(state, new_crtc_state, 0);
}
/**
@@ -15272,6 +15336,11 @@ static int intel_crtc_init(struct drm_i915_private *dev_priv, enum pipe pipe)
intel_color_init(intel_crtc);
+ pm_qos_add_request(&intel_crtc->pm_qos, PM_QOS_CPU_DMA_LATENCY,
+ PM_QOS_DEFAULT_VALUE);
+ drm_vblank_work_init(&crtc_state->vblank_work,
+ &intel_crtc->base, intel_crtc_vblank_work);
+
WARN_ON(drm_crtc_index(&intel_crtc->base) != intel_crtc->pipe);
return 0;
@@ -16799,10 +16868,13 @@ static void intel_modeset_readout_hw_state(struct drm_device *dev)
for_each_intel_crtc(dev, crtc) {
struct intel_crtc_state *crtc_state =
to_intel_crtc_state(crtc->base.state);
+ struct drm_vblank_work save_vblank_work =
+ crtc_state->vblank_work;
__drm_atomic_helper_crtc_destroy_state(&crtc_state->base);
memset(crtc_state, 0, sizeof(*crtc_state));
__drm_atomic_helper_crtc_reset(&crtc->base, &crtc_state->base);
+ crtc_state->vblank_work = save_vblank_work;
crtc_state->base.active = crtc_state->base.enable =
dev_priv->display.get_pipe_config(crtc, crtc_state);
diff --git a/drivers/gpu/drm/i915/display/intel_display.h b/drivers/gpu/drm/i915/display/intel_display.h
index 33fd523c4622..8529687c59d6 100644
--- a/drivers/gpu/drm/i915/display/intel_display.h
+++ b/drivers/gpu/drm/i915/display/intel_display.h
@@ -41,6 +41,7 @@ struct drm_i915_private;
struct drm_modeset_acquire_ctx;
struct drm_plane;
struct drm_plane_state;
+struct drm_vblank_work;
struct i915_ggtt_view;
struct intel_crtc;
struct intel_crtc_state;
@@ -403,6 +404,14 @@ enum phy_fia {
(__i)++) \
for_each_if(plane)
+#define for_each_old_intel_crtc_in_state(__state, crtc, old_crtc_state, __i) \
+ for ((__i) = 0; \
+ (__i) < (__state)->base.dev->mode_config.num_crtc && \
+ ((crtc) = to_intel_crtc((__state)->base.crtcs[__i].ptr), \
+ (old_crtc_state) = to_intel_crtc_state((__state)->base.crtcs[__i].old_state), 1); \
+ (__i)++) \
+ for_each_if(crtc)
+
#define for_each_new_intel_crtc_in_state(__state, crtc, new_crtc_state, __i) \
for ((__i) = 0; \
(__i) < (__state)->base.dev->mode_config.num_crtc && \
@@ -564,6 +573,8 @@ unsigned int i9xx_plane_max_stride(struct intel_plane *plane,
u32 pixel_format, u64 modifier,
unsigned int rotation);
int bdw_get_pipemisc_bpp(struct intel_crtc *crtc);
+void intel_crtc_vblank_work(struct drm_vblank_work *work,
+ u64 count);
struct intel_display_error_state *
intel_display_capture_error_state(struct drm_i915_private *dev_priv);
diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
index 36da0bbe99f1..9117f0a51dde 100644
--- a/drivers/gpu/drm/i915/display/intel_display_types.h
+++ b/drivers/gpu/drm/i915/display/intel_display_types.h
@@ -512,6 +512,8 @@ struct intel_atomic_state {
struct i915_sw_fence commit_ready;
struct llist_node freed;
+
+ atomic_t cleanup_count;
};
struct intel_plane_state {
@@ -992,6 +994,8 @@ struct intel_crtc_state {
/* Forward Error correction State */
bool fec_enable;
+ struct drm_vblank_work vblank_work;
+ struct intel_atomic_state *state;
u64 put_domains;
};
@@ -1035,6 +1039,8 @@ struct intel_crtc {
/* scalers available on this crtc */
int num_scalers;
+
+ struct pm_qos_request pm_qos;
};
struct intel_plane {
diff --git a/drivers/gpu/drm/i915/display/intel_sprite.c b/drivers/gpu/drm/i915/display/intel_sprite.c
index ef18649e15a0..9a6e07512a40 100644
--- a/drivers/gpu/drm/i915/display/intel_sprite.c
+++ b/drivers/gpu/drm/i915/display/intel_sprite.c
@@ -72,6 +72,44 @@ int intel_usecs_to_scanlines(const struct drm_display_mode *adjusted_mode,
1000 * adjusted_mode->crtc_htotal);
}
+bool intel_crtc_need_lut_load(const struct intel_crtc_state *crtc_state);
+
+static bool intel_crtc_need_vblank_work(struct intel_atomic_state *state,
+ const struct intel_crtc_state *crtc_state)
+{
+ if (!crtc_state->base.active)
+ return false;
+
+ return intel_crtc_need_lut_load(crtc_state) ||
+ crtc_state->wm.need_postvbl_update;
+}
+
+static int intel_crtc_schedule_vblank_work(struct intel_atomic_state *state,
+ struct intel_crtc_state *new_crtc_state,
+ u64 vbl_count)
+{
+ int ret;
+
+ if (WARN_ON(!new_crtc_state->base.active))
+ return -EBUSY;
+
+ /*
+ * drm_atomic_helper_swap_state() has already made
+ * new_crtc_state->base.state NULL hence we need our own pointer.
+ */
+ new_crtc_state->state = state;
+ atomic_inc(&state->cleanup_count);
+
+ ret = drm_vblank_work_schedule(&new_crtc_state->vblank_work,
+ vbl_count, false);
+ if (ret) {
+ new_crtc_state->state = NULL;
+ atomic_dec(&state->cleanup_count);
+ }
+
+ return ret;
+}
+
/* FIXME: We should instead only take spinlocks once for the entire update
* instead of once per mmio. */
#if IS_ENABLED(CONFIG_PROVE_LOCKING)
@@ -195,13 +233,15 @@ void intel_pipe_update_start(const struct intel_crtc_state *new_crtc_state)
/**
* intel_pipe_update_end() - end update of a set of display registers
+ * @state: the atomic state
* @new_crtc_state: the new crtc state
*
* Mark the end of an update started with intel_pipe_update_start(). This
* re-enables interrupts and verifies the update was actually completed
* before a vblank.
*/
-void intel_pipe_update_end(struct intel_crtc_state *new_crtc_state)
+int intel_pipe_update_end(struct intel_atomic_state *state,
+ struct intel_crtc_state *new_crtc_state)
{
struct intel_crtc *crtc = to_intel_crtc(new_crtc_state->base.crtc);
enum pipe pipe = crtc->pipe;
@@ -209,6 +249,8 @@ void intel_pipe_update_end(struct intel_crtc_state *new_crtc_state)
u32 end_vbl_count = intel_crtc_get_vblank_counter(crtc);
ktime_t end_vbl_time = ktime_get();
struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
+ u64 vbl_count;
+ int ret;
trace_i915_pipe_update_end(crtc, end_vbl_count, scanline_end);
@@ -221,15 +263,24 @@ void intel_pipe_update_end(struct intel_crtc_state *new_crtc_state)
spin_lock(&crtc->base.dev->event_lock);
drm_crtc_arm_vblank_event(&crtc->base, new_crtc_state->base.event);
+ vbl_count = new_crtc_state->base.event->sequence;
spin_unlock(&crtc->base.dev->event_lock);
new_crtc_state->base.event = NULL;
+ } else if (intel_crtc_need_vblank_work(state, new_crtc_state)) {
+ vbl_count = drm_crtc_accurate_vblank_count(&crtc->base) + 1;
}
+ if (intel_crtc_need_vblank_work(state, new_crtc_state))
+ ret = intel_crtc_schedule_vblank_work(state, new_crtc_state,
+ vbl_count);
+ else
+ ret = 1;
+
local_irq_enable();
if (intel_vgpu_active(dev_priv))
- return;
+ return ret;
if (crtc->debug.start_vbl_count &&
crtc->debug.start_vbl_count != end_vbl_count) {
@@ -248,6 +299,7 @@ void intel_pipe_update_end(struct intel_crtc_state *new_crtc_state)
ktime_us_delta(end_vbl_time, crtc->debug.start_vbl_time),
VBLANK_EVASION_TIME_US);
#endif
+ return ret;
}
int intel_plane_check_stride(const struct intel_plane_state *plane_state)
diff --git a/drivers/gpu/drm/i915/display/intel_sprite.h b/drivers/gpu/drm/i915/display/intel_sprite.h
index 093a2d156f1e..58816087b010 100644
--- a/drivers/gpu/drm/i915/display/intel_sprite.h
+++ b/drivers/gpu/drm/i915/display/intel_sprite.h
@@ -14,6 +14,7 @@ struct drm_device;
struct drm_display_mode;
struct drm_file;
struct drm_i915_private;
+struct intel_atomic_state;
struct intel_crtc_state;
struct intel_plane_state;
@@ -25,7 +26,8 @@ struct intel_plane *intel_sprite_plane_create(struct drm_i915_private *dev_priv,
int intel_sprite_set_colorkey_ioctl(struct drm_device *dev, void *data,
struct drm_file *file_priv);
void intel_pipe_update_start(const struct intel_crtc_state *new_crtc_state);
-void intel_pipe_update_end(struct intel_crtc_state *new_crtc_state);
+int intel_pipe_update_end(struct intel_atomic_state *state,
+ struct intel_crtc_state *new_crtc_state);
int intel_plane_check_stride(const struct intel_plane_state *plane_state);
int intel_plane_check_src_coordinates(struct intel_plane_state *plane_state);
int chv_plane_check_rotation(const struct intel_plane_state *plane_state);
diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 1af4eba968c0..3b046088d2b2 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -1752,6 +1752,7 @@ static int i915_drm_suspend(struct drm_device *dev)
pci_save_state(pdev);
intel_display_suspend(dev);
+ msleep(500);
intel_dp_mst_suspend(dev_priv);
--
2.21.0
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