| Message ID | 20190917200443.64481-2-sean@poorly.run (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [1/2] drm: Fix kerneldoc and remove unused struct member in self_refresh helper | expand |
On Tue, Sep 17, 2019 at 04:04:33PM -0400, Sean Paul wrote: > From: Sean Paul <seanpaul@chromium.org> > > Currently the self refresh idle timer is a const set by the crtc. This > is fine if the self refresh entry/exit times are well-known for all > panels used on that crtc. However panels and workloads can vary quite a > bit, and a timeout which works well for one doesn't work well for > another. > > In the extreme, if the timeout is too short we could get in a situation > where the self refresh exits are taking so long we queue up a self refresh > entry before the exit commit is even finished. > > This patch changes the idle timeout to a moving average of the entry > times + a moving average of exit times + the crtc constant. > > This patch was tested on rockchip, with a "kevin" CrOS panel the idle > delay averages out to about ~235ms (35 entry + 100 exit + 100 const). On > the same board, the "bob" panel idle delay lands around ~340ms (90 entry > + 150 exit + 100 const). > > Signed-off-by: Sean Paul <seanpaul@chromium.org> > --- > drivers/gpu/drm/drm_atomic_helper.c | 20 +++++++ > drivers/gpu/drm/drm_self_refresh_helper.c | 71 ++++++++++++++++++++++- > include/drm/drm_self_refresh_helper.h | 2 + > 3 files changed, 92 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c > index 9d7e4da6c292..3f13fa9a9e24 100644 > --- a/drivers/gpu/drm/drm_atomic_helper.c > +++ b/drivers/gpu/drm/drm_atomic_helper.c > @@ -26,6 +26,7 @@ > */ > > #include <linux/dma-fence.h> > +#include <linux/ktime.h> > > #include <drm/drm_atomic.h> > #include <drm/drm_atomic_helper.h> > @@ -1570,9 +1571,23 @@ 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; > + ktime_t start; > + s64 commit_time_ms; > > funcs = dev->mode_config.helper_private; > > + /* > + * We're measuring the _entire_ commit, so the time will vary depending > + * on how many fences and objects are involved. For the purposes of self > + * refresh, this is desirable since it'll give us an idea of how > + * congested things are. This will inform our decision on how often we > + * should enter self refresh after idle. > + * > + * These times will be averaged out in the self refresh helpers to avoid > + * overreacting over one outlier frame > + */ > + start = ktime_get(); > + > drm_atomic_helper_wait_for_fences(dev, old_state, false); > > drm_atomic_helper_wait_for_dependencies(old_state); > @@ -1582,6 +1597,11 @@ static void commit_tail(struct drm_atomic_state *old_state) > else > drm_atomic_helper_commit_tail(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); > + > drm_atomic_helper_commit_cleanup_done(old_state); > > drm_atomic_state_put(old_state); > diff --git a/drivers/gpu/drm/drm_self_refresh_helper.c b/drivers/gpu/drm/drm_self_refresh_helper.c > index 9095cebf2147..522430f8eef1 100644 > --- a/drivers/gpu/drm/drm_self_refresh_helper.c > +++ b/drivers/gpu/drm/drm_self_refresh_helper.c > @@ -5,6 +5,7 @@ > * Authors: > * Sean Paul <seanpaul@chromium.org> > */ > +#include <linux/average.h> > #include <linux/bitops.h> > #include <linux/slab.h> > #include <linux/workqueue.h> > @@ -50,10 +51,16 @@ > * atomic_check when &drm_crtc_state.self_refresh_active is true. > */ > > +DECLARE_EWMA(psr_time, 4, 4) > + > struct drm_self_refresh_data { > struct drm_crtc *crtc; > struct delayed_work entry_work; > unsigned int entry_delay_ms; > + > + struct mutex avg_mutex; > + struct ewma_psr_time entry_avg_ms; > + struct ewma_psr_time exit_avg_ms; > }; > > static void drm_self_refresh_helper_entry_work(struct work_struct *work) > @@ -121,6 +128,59 @@ static void drm_self_refresh_helper_entry_work(struct work_struct *work) > drm_modeset_acquire_fini(&ctx); > } > > +/** > + * 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 > + * > + * 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) > +{ > + struct drm_crtc *crtc; > + struct drm_crtc_state *old_crtc_state, *new_crtc_state; > + int i; > + > + for_each_oldnew_crtc_in_state(state, crtc, old_crtc_state, > + new_crtc_state, 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) > + continue; > + > + if (new_crtc_state->self_refresh_active) > + time = &sr_data->entry_avg_ms; > + else > + time = &sr_data->exit_avg_ms; > + > + /* > + * It might be nice if we could rely on &drm_crtc.mutex to > + * protect &drm_self_refresh_data.exit_avg_ms, as we do with > + * &drm_self_refresh_data.entry_avg_ms, but there are a few > + * reasons why a separate lock is a better choice: > + * - We can't rely on &drm_crtc.mutex being held here if we're > + * doing a nonblocking commit > + * - We can't grab &drm_crtc.mutex here since drm_modeset_lock() > + * doesn't tell us whether the lock was already held in the > + * acquire context (it eats -EALREADY), so we can't tell if we > + * should drop it or not > + * - We don't need such a heavy-handed lock for what we're > + * trying to do here, commit ordering doesn't matter, so a > + * point-of-use lock will be less contentious > + */ This comment here feels rather misplaced, I think better to put that into the commit message. Elaborate locking analysis in code comments tends to not age well ime. > + mutex_lock(&sr_data->avg_mutex); > + ewma_psr_time_add(time, commit_time_ms); > + mutex_unlock(&sr_data->avg_mutex); > + } > +} > +EXPORT_SYMBOL(drm_self_refresh_helper_update_avg_times); > + > /** > * drm_self_refresh_helper_alter_state - Alters the atomic state for SR exit > * @state: the state currently being checked > @@ -152,6 +212,7 @@ void drm_self_refresh_helper_alter_state(struct drm_atomic_state *state) > > for_each_new_crtc_in_state(state, crtc, crtc_state, i) { > struct drm_self_refresh_data *sr_data; > + unsigned int delay; > > /* Don't trigger the entry timer when we're already in SR */ > if (crtc_state->self_refresh_active) > @@ -161,8 +222,13 @@ void drm_self_refresh_helper_alter_state(struct drm_atomic_state *state) > if (!sr_data) > continue; > > + mutex_lock(&sr_data->avg_mutex); > + delay = ewma_psr_time_read(&sr_data->entry_avg_ms) + > + ewma_psr_time_read(&sr_data->exit_avg_ms) + > + sr_data->entry_delay_ms; Since you auto-tune now, I'd remove the entry_delay_ms thing outright, and just use 2x the entry+exit times for this. That would scale lot better from real quick panels that take only 1 frame to enter/exit (i.e. no real delay) ot real horrrors that might take even longer than the panels you have. Adding a constant 100ms still assumes that entry+exit aren't too far away from that 100ms value you hardcoded in drivers. Should we have a debug print somewhere that tells us the self-refresh delay? I'd expect a "why am I not entering sr?" moment with this otherwise. > + mutex_unlock(&sr_data->avg_mutex); > mod_delayed_work(system_wq, &sr_data->entry_work, > - msecs_to_jiffies(sr_data->entry_delay_ms)); > + msecs_to_jiffies(delay)); > } > } > EXPORT_SYMBOL(drm_self_refresh_helper_alter_state); > @@ -191,6 +257,9 @@ int drm_self_refresh_helper_init(struct drm_crtc *crtc, > drm_self_refresh_helper_entry_work); > sr_data->entry_delay_ms = entry_delay_ms; > sr_data->crtc = crtc; > + mutex_init(&sr_data->avg_mutex); > + ewma_psr_time_init(&sr_data->entry_avg_ms); > + ewma_psr_time_init(&sr_data->exit_avg_ms); > > crtc->self_refresh_data = sr_data; > return 0; > diff --git a/include/drm/drm_self_refresh_helper.h b/include/drm/drm_self_refresh_helper.h > index 397a583ccca7..ff777690c564 100644 > --- a/include/drm/drm_self_refresh_helper.h > +++ b/include/drm/drm_self_refresh_helper.h > @@ -12,6 +12,8 @@ struct drm_atomic_state; > 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); > > int drm_self_refresh_helper_init(struct drm_crtc *crtc, > unsigned int entry_delay_ms); With the bikesheds addressed somehow: Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> > -- > Sean Paul, Software Engineer, Google / Chromium OS >
diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c index 9d7e4da6c292..3f13fa9a9e24 100644 --- a/drivers/gpu/drm/drm_atomic_helper.c +++ b/drivers/gpu/drm/drm_atomic_helper.c @@ -26,6 +26,7 @@ */ #include <linux/dma-fence.h> +#include <linux/ktime.h> #include <drm/drm_atomic.h> #include <drm/drm_atomic_helper.h> @@ -1570,9 +1571,23 @@ 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; + ktime_t start; + s64 commit_time_ms; funcs = dev->mode_config.helper_private; + /* + * We're measuring the _entire_ commit, so the time will vary depending + * on how many fences and objects are involved. For the purposes of self + * refresh, this is desirable since it'll give us an idea of how + * congested things are. This will inform our decision on how often we + * should enter self refresh after idle. + * + * These times will be averaged out in the self refresh helpers to avoid + * overreacting over one outlier frame + */ + start = ktime_get(); + drm_atomic_helper_wait_for_fences(dev, old_state, false); drm_atomic_helper_wait_for_dependencies(old_state); @@ -1582,6 +1597,11 @@ static void commit_tail(struct drm_atomic_state *old_state) else drm_atomic_helper_commit_tail(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); + drm_atomic_helper_commit_cleanup_done(old_state); drm_atomic_state_put(old_state); diff --git a/drivers/gpu/drm/drm_self_refresh_helper.c b/drivers/gpu/drm/drm_self_refresh_helper.c index 9095cebf2147..522430f8eef1 100644 --- a/drivers/gpu/drm/drm_self_refresh_helper.c +++ b/drivers/gpu/drm/drm_self_refresh_helper.c @@ -5,6 +5,7 @@ * Authors: * Sean Paul <seanpaul@chromium.org> */ +#include <linux/average.h> #include <linux/bitops.h> #include <linux/slab.h> #include <linux/workqueue.h> @@ -50,10 +51,16 @@ * atomic_check when &drm_crtc_state.self_refresh_active is true. */ +DECLARE_EWMA(psr_time, 4, 4) + struct drm_self_refresh_data { struct drm_crtc *crtc; struct delayed_work entry_work; unsigned int entry_delay_ms; + + struct mutex avg_mutex; + struct ewma_psr_time entry_avg_ms; + struct ewma_psr_time exit_avg_ms; }; static void drm_self_refresh_helper_entry_work(struct work_struct *work) @@ -121,6 +128,59 @@ static void drm_self_refresh_helper_entry_work(struct work_struct *work) drm_modeset_acquire_fini(&ctx); } +/** + * 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 + * + * 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) +{ + struct drm_crtc *crtc; + struct drm_crtc_state *old_crtc_state, *new_crtc_state; + int i; + + for_each_oldnew_crtc_in_state(state, crtc, old_crtc_state, + new_crtc_state, 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) + continue; + + if (new_crtc_state->self_refresh_active) + time = &sr_data->entry_avg_ms; + else + time = &sr_data->exit_avg_ms; + + /* + * It might be nice if we could rely on &drm_crtc.mutex to + * protect &drm_self_refresh_data.exit_avg_ms, as we do with + * &drm_self_refresh_data.entry_avg_ms, but there are a few + * reasons why a separate lock is a better choice: + * - We can't rely on &drm_crtc.mutex being held here if we're + * doing a nonblocking commit + * - We can't grab &drm_crtc.mutex here since drm_modeset_lock() + * doesn't tell us whether the lock was already held in the + * acquire context (it eats -EALREADY), so we can't tell if we + * should drop it or not + * - We don't need such a heavy-handed lock for what we're + * trying to do here, commit ordering doesn't matter, so a + * point-of-use lock will be less contentious + */ + mutex_lock(&sr_data->avg_mutex); + ewma_psr_time_add(time, commit_time_ms); + mutex_unlock(&sr_data->avg_mutex); + } +} +EXPORT_SYMBOL(drm_self_refresh_helper_update_avg_times); + /** * drm_self_refresh_helper_alter_state - Alters the atomic state for SR exit * @state: the state currently being checked @@ -152,6 +212,7 @@ void drm_self_refresh_helper_alter_state(struct drm_atomic_state *state) for_each_new_crtc_in_state(state, crtc, crtc_state, i) { struct drm_self_refresh_data *sr_data; + unsigned int delay; /* Don't trigger the entry timer when we're already in SR */ if (crtc_state->self_refresh_active) @@ -161,8 +222,13 @@ void drm_self_refresh_helper_alter_state(struct drm_atomic_state *state) if (!sr_data) continue; + mutex_lock(&sr_data->avg_mutex); + delay = ewma_psr_time_read(&sr_data->entry_avg_ms) + + ewma_psr_time_read(&sr_data->exit_avg_ms) + + sr_data->entry_delay_ms; + mutex_unlock(&sr_data->avg_mutex); mod_delayed_work(system_wq, &sr_data->entry_work, - msecs_to_jiffies(sr_data->entry_delay_ms)); + msecs_to_jiffies(delay)); } } EXPORT_SYMBOL(drm_self_refresh_helper_alter_state); @@ -191,6 +257,9 @@ int drm_self_refresh_helper_init(struct drm_crtc *crtc, drm_self_refresh_helper_entry_work); sr_data->entry_delay_ms = entry_delay_ms; sr_data->crtc = crtc; + mutex_init(&sr_data->avg_mutex); + ewma_psr_time_init(&sr_data->entry_avg_ms); + ewma_psr_time_init(&sr_data->exit_avg_ms); crtc->self_refresh_data = sr_data; return 0; diff --git a/include/drm/drm_self_refresh_helper.h b/include/drm/drm_self_refresh_helper.h index 397a583ccca7..ff777690c564 100644 --- a/include/drm/drm_self_refresh_helper.h +++ b/include/drm/drm_self_refresh_helper.h @@ -12,6 +12,8 @@ struct drm_atomic_state; 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); int drm_self_refresh_helper_init(struct drm_crtc *crtc, unsigned int entry_delay_ms);