Commit 86de88cf authored by Rob Clark's avatar Rob Clark Committed by Sean Paul
Browse files

drm/atomic: fix self-refresh helpers crtc state dereference 



drm_self_refresh_helper_update_avg_times() was incorrectly accessing the
new incoming state after drm_atomic_helper_commit_hw_done().  But this
state might have already been superceeded by an !nonblock atomic update
resulting in dereferencing an already free'd crtc_state.

TODO I *think* this will more or less do the right thing.. althought I'm
not 100% sure if, for example, we enter psr in a nonblock commit, and
then leave psr in a !nonblock commit that overtakes the completion of
the nonblock commit.  Not sure if this sort of scenario can happen in
practice.  But not crashing is better than crashing, so I guess we
should either take this patch or rever the self-refresh helpers until
Sean can figure out a better solution.

Fixes: d4da4e33 ("drm: Measure Self Refresh Entry/Exit times to avoid thrashing")
Cc: Sean Paul <seanpaul@chromium.org>
Signed-off-by: default avatarRob Clark <robdclark@chromium.org>
[seanpaul fixed up some checkpatch warns]
Signed-off-by: default avatarSean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20191104173737.142558-1-robdclark@gmail.com
parent b330f397

drivers/gpu/drm/drm_atomic_helper.c

+14 −1
Original line number Diff line number Diff line
@@ -1581,8 +1581,11 @@ static void commit_tail(struct drm_atomic_state *old_state) 
{

	struct drm_device *dev = old_state->dev;

	const struct drm_mode_config_helper_funcs *funcs;

	struct drm_crtc_state *new_crtc_state;

	struct drm_crtc *crtc;

	ktime_t start;

	s64 commit_time_ms;

	unsigned int i, new_self_refresh_mask = 0;



	funcs = dev->mode_config.helper_private;
@@ -1602,6 +1605,15 @@ static void commit_tail(struct drm_atomic_state *old_state) 


	drm_atomic_helper_wait_for_dependencies(old_state);



	/*

	 * We cannot safely access new_crtc_state after

	 * drm_atomic_helper_commit_hw_done() so figure out which crtc's have

	 * self-refresh active beforehand:

	 */

	for_each_new_crtc_in_state(old_state, crtc, new_crtc_state, i)

		if (new_crtc_state->self_refresh_active)

			new_self_refresh_mask |= BIT(i);



	if (funcs && funcs->atomic_commit_tail)

		funcs->atomic_commit_tail(old_state);

	else
@@ -1610,7 +1622,8 @@ static void commit_tail(struct drm_atomic_state *old_state) 
	commit_time_ms = ktime_ms_delta(ktime_get(), start);

	if (commit_time_ms > 0)

		drm_self_refresh_helper_update_avg_times(old_state,

						 (unsigned long)commit_time_ms);

						 (unsigned long)commit_time_ms,

						 new_self_refresh_mask);



	drm_atomic_helper_commit_cleanup_done(old_state);

drivers/gpu/drm/drm_self_refresh_helper.c

+11 −7
Original line number Diff line number Diff line
@@ -133,29 +133,33 @@ out_drop_locks: 
 * drm_self_refresh_helper_update_avg_times - Updates a crtc's SR time averages

 * @state: the state which has just been applied to hardware

 * @commit_time_ms: the amount of time in ms that this commit took to complete

 * @new_self_refresh_mask: bitmask of crtc's that have self_refresh_active in

 *    new state

 *

 * Called after &drm_mode_config_funcs.atomic_commit_tail, this function will

 * update the average entry/exit self refresh times on self refresh transitions.

 * These averages will be used when calculating how long to delay before

 * entering self refresh mode after activity.

 */

void drm_self_refresh_helper_update_avg_times(struct drm_atomic_state *state,

					      unsigned int commit_time_ms)

void

drm_self_refresh_helper_update_avg_times(struct drm_atomic_state *state,

					 unsigned int commit_time_ms,

					 unsigned int new_self_refresh_mask)

{

	struct drm_crtc *crtc;

	struct drm_crtc_state *old_crtc_state, *new_crtc_state;

	struct drm_crtc_state *old_crtc_state;

	int i;



	for_each_oldnew_crtc_in_state(state, crtc, old_crtc_state,

				      new_crtc_state, i) {

	for_each_old_crtc_in_state(state, crtc, old_crtc_state, i) {

		bool new_self_refresh_active = new_self_refresh_mask & BIT(i);

		struct drm_self_refresh_data *sr_data = crtc->self_refresh_data;

		struct ewma_psr_time *time;



		if (old_crtc_state->self_refresh_active ==

		    new_crtc_state->self_refresh_active)

		    new_self_refresh_active)

			continue;



		if (new_crtc_state->self_refresh_active)

		if (new_self_refresh_active)

			time = &sr_data->entry_avg_ms;

		else

			time = &sr_data->exit_avg_ms;

include/drm/drm_self_refresh_helper.h

+2 −1
Original line number Diff line number Diff line
@@ -13,7 +13,8 @@ struct drm_crtc; 


void drm_self_refresh_helper_alter_state(struct drm_atomic_state *state);

void drm_self_refresh_helper_update_avg_times(struct drm_atomic_state *state,

					      unsigned int commit_time_ms);

					unsigned int commit_time_ms,

					unsigned int new_self_refresh_mask);



int drm_self_refresh_helper_init(struct drm_crtc *crtc);

void drm_self_refresh_helper_cleanup(struct drm_crtc *crtc);

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