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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: d4da4e3334 ("drm: Measure Self Refresh Entry/Exit times to avoid thrashing")
Cc: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>
[seanpaul fixed up some checkpatch warns]
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20191104173737.142558-1-robdclark@gmail.com
This commit is contained in:
Rob Clark 2019-11-04 09:37:36 -08:00 committed by Sean Paul
parent b330f3972f
commit 86de88cfeb
3 changed files with 27 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
drivers/gpu/drm/drm_atomic_helper.c
View File

@ -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);

18
drivers/gpu/drm/drm_self_refresh_helper.c
View File

@ -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;

3
include/drm/drm_self_refresh_helper.h
View File

@ -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);