From b3d91800d9ac35014e0349292273a6fa7938d402 Mon Sep 17 00:00:00 2001 From: Krishna Manikandan Date: Fri, 16 Oct 2020 19:40:43 +0530 Subject: drm/msm: Fix race condition in msm driver with async layer updates When there are back to back commits with async cursor update, there is a case where second commit can program the DPU hw blocks while first didn't complete flushing config to HW. Synchronize the compositions such that second commit waits until first commit flushes the composition. This change also introduces per crtc commit lock, such that commits on different crtcs are not blocked by each other. Changes in v2: - Use an array of mutexes in kms to handle commit lock per crtc. (Rob Clark) Changes in v3: - Add wrapper functions to handle lock and unlock of commit_lock for each crtc. (Rob Clark) Signed-off-by: Krishna Manikandan Reviewed-by: Rob Clark Signed-off-by: Rob Clark --- drivers/gpu/drm/msm/msm_atomic.c | 37 ++++++++++++++++++++++++------------- 1 file changed, 24 insertions(+), 13 deletions(-) (limited to 'drivers/gpu/drm/msm/msm_atomic.c') diff --git a/drivers/gpu/drm/msm/msm_atomic.c b/drivers/gpu/drm/msm/msm_atomic.c index 561bfa48841c..575e9af9b6fc 100644 --- a/drivers/gpu/drm/msm/msm_atomic.c +++ b/drivers/gpu/drm/msm/msm_atomic.c @@ -55,16 +55,32 @@ static void vblank_put(struct msm_kms *kms, unsigned crtc_mask) } } +static void lock_crtcs(struct msm_kms *kms, unsigned int crtc_mask) +{ + struct drm_crtc *crtc; + + for_each_crtc_mask(kms->dev, crtc, crtc_mask) + mutex_lock(&kms->commit_lock[drm_crtc_index(crtc)]); +} + +static void unlock_crtcs(struct msm_kms *kms, unsigned int crtc_mask) +{ + struct drm_crtc *crtc; + + for_each_crtc_mask(kms->dev, crtc, crtc_mask) + mutex_unlock(&kms->commit_lock[drm_crtc_index(crtc)]); +} + static void msm_atomic_async_commit(struct msm_kms *kms, int crtc_idx) { unsigned crtc_mask = BIT(crtc_idx); trace_msm_atomic_async_commit_start(crtc_mask); - mutex_lock(&kms->commit_lock); + lock_crtcs(kms, crtc_mask); if (!(kms->pending_crtc_mask & crtc_mask)) { - mutex_unlock(&kms->commit_lock); + unlock_crtcs(kms, crtc_mask); goto out; } @@ -79,7 +95,6 @@ static void msm_atomic_async_commit(struct msm_kms *kms, int crtc_idx) */ trace_msm_atomic_flush_commit(crtc_mask); kms->funcs->flush_commit(kms, crtc_mask); - mutex_unlock(&kms->commit_lock); /* * Wait for flush to complete: @@ -90,9 +105,8 @@ static void msm_atomic_async_commit(struct msm_kms *kms, int crtc_idx) vblank_put(kms, crtc_mask); - mutex_lock(&kms->commit_lock); kms->funcs->complete_commit(kms, crtc_mask); - mutex_unlock(&kms->commit_lock); + unlock_crtcs(kms, crtc_mask); kms->funcs->disable_commit(kms); out: @@ -189,12 +203,11 @@ void msm_atomic_commit_tail(struct drm_atomic_state *state) * Ensure any previous (potentially async) commit has * completed: */ + lock_crtcs(kms, crtc_mask); trace_msm_atomic_wait_flush_start(crtc_mask); kms->funcs->wait_flush(kms, crtc_mask); trace_msm_atomic_wait_flush_finish(crtc_mask); - mutex_lock(&kms->commit_lock); - /* * Now that there is no in-progress flush, prepare the * current update: @@ -232,8 +245,7 @@ void msm_atomic_commit_tail(struct drm_atomic_state *state) } kms->funcs->disable_commit(kms); - mutex_unlock(&kms->commit_lock); - + unlock_crtcs(kms, crtc_mask); /* * At this point, from drm core's perspective, we * are done with the atomic update, so we can just @@ -260,8 +272,7 @@ void msm_atomic_commit_tail(struct drm_atomic_state *state) */ trace_msm_atomic_flush_commit(crtc_mask); kms->funcs->flush_commit(kms, crtc_mask); - mutex_unlock(&kms->commit_lock); - + unlock_crtcs(kms, crtc_mask); /* * Wait for flush to complete: */ @@ -271,9 +282,9 @@ void msm_atomic_commit_tail(struct drm_atomic_state *state) vblank_put(kms, crtc_mask); - mutex_lock(&kms->commit_lock); + lock_crtcs(kms, crtc_mask); kms->funcs->complete_commit(kms, crtc_mask); - mutex_unlock(&kms->commit_lock); + unlock_crtcs(kms, crtc_mask); kms->funcs->disable_commit(kms); drm_atomic_helper_commit_hw_done(state); -- cgit From cb21f3f882ad12811331c1067b9acfc4dd359d3f Mon Sep 17 00:00:00 2001 From: Rob Clark Date: Tue, 20 Oct 2020 15:26:00 -0700 Subject: drm/msm/atomic: Drop per-CRTC locks in reverse order lockdep dislikes seeing locks unwound in a non-nested fashion. Fixes: b3d91800d9ac ("drm/msm: Fix race condition in msm driver with async layer updates") Signed-off-by: Rob Clark Reviewed-by: Abhinav Kumar --- drivers/gpu/drm/msm/msm_atomic.c | 2 +- drivers/gpu/drm/msm/msm_kms.h | 4 ++++ include/drm/drm_crtc.h | 10 ++++++++++ 3 files changed, 15 insertions(+), 1 deletion(-) (limited to 'drivers/gpu/drm/msm/msm_atomic.c') diff --git a/drivers/gpu/drm/msm/msm_atomic.c b/drivers/gpu/drm/msm/msm_atomic.c index 575e9af9b6fc..93d39608a073 100644 --- a/drivers/gpu/drm/msm/msm_atomic.c +++ b/drivers/gpu/drm/msm/msm_atomic.c @@ -67,7 +67,7 @@ static void unlock_crtcs(struct msm_kms *kms, unsigned int crtc_mask) { struct drm_crtc *crtc; - for_each_crtc_mask(kms->dev, crtc, crtc_mask) + for_each_crtc_mask_reverse(kms->dev, crtc, crtc_mask) mutex_unlock(&kms->commit_lock[drm_crtc_index(crtc)]); } diff --git a/drivers/gpu/drm/msm/msm_kms.h b/drivers/gpu/drm/msm/msm_kms.h index 2049847b6642..977ea96e383b 100644 --- a/drivers/gpu/drm/msm/msm_kms.h +++ b/drivers/gpu/drm/msm/msm_kms.h @@ -196,4 +196,8 @@ int dpu_mdss_init(struct drm_device *dev); drm_for_each_crtc(crtc, dev) \ for_each_if (drm_crtc_mask(crtc) & (crtc_mask)) +#define for_each_crtc_mask_reverse(dev, crtc, crtc_mask) \ + drm_for_each_crtc_reverse(crtc, dev) \ + for_each_if (drm_crtc_mask(crtc) & (crtc_mask)) + #endif /* __MSM_KMS_H__ */ diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h index 59b51a09cae6..cd42f79b2890 100644 --- a/include/drm/drm_crtc.h +++ b/include/drm/drm_crtc.h @@ -1266,4 +1266,14 @@ static inline struct drm_crtc *drm_crtc_find(struct drm_device *dev, #define drm_for_each_crtc(crtc, dev) \ list_for_each_entry(crtc, &(dev)->mode_config.crtc_list, head) +/** + * drm_for_each_crtc_reverse - iterate over all CRTCs in reverse order + * @crtc: a &struct drm_crtc as the loop cursor + * @dev: the &struct drm_device + * + * Iterate over all CRTCs of @dev. + */ +#define drm_for_each_crtc_reverse(crtc, dev) \ + list_for_each_entry_reverse(crtc, &(dev)->mode_config.crtc_list, head) + #endif /* __DRM_CRTC_H__ */ -- cgit From 363bcec913d82703be6ae0ad5fe5488532f5cdac Mon Sep 17 00:00:00 2001 From: Rob Clark Date: Mon, 19 Oct 2020 14:10:53 -0700 Subject: drm/msm/atomic: Convert to per-CRTC kthread_work Use a SCHED_FIFO kthread_worker for async atomic commits. We have a hard deadline if we don't want to miss a frame. Signed-off-by: Rob Clark --- drivers/gpu/drm/msm/msm_atomic.c | 25 ++++++++++++++++++++----- drivers/gpu/drm/msm/msm_drv.h | 3 ++- drivers/gpu/drm/msm/msm_kms.h | 17 +++++++++++++---- 3 files changed, 35 insertions(+), 10 deletions(-) (limited to 'drivers/gpu/drm/msm/msm_atomic.c') diff --git a/drivers/gpu/drm/msm/msm_atomic.c b/drivers/gpu/drm/msm/msm_atomic.c index 93d39608a073..6a326761dc4a 100644 --- a/drivers/gpu/drm/msm/msm_atomic.c +++ b/drivers/gpu/drm/msm/msm_atomic.c @@ -117,14 +117,13 @@ static enum hrtimer_restart msm_atomic_pending_timer(struct hrtimer *t) { struct msm_pending_timer *timer = container_of(t, struct msm_pending_timer, timer); - struct msm_drm_private *priv = timer->kms->dev->dev_private; - queue_work(priv->wq, &timer->work); + kthread_queue_work(timer->worker, &timer->work); return HRTIMER_NORESTART; } -static void msm_atomic_pending_work(struct work_struct *work) +static void msm_atomic_pending_work(struct kthread_work *work) { struct msm_pending_timer *timer = container_of(work, struct msm_pending_timer, work); @@ -132,14 +131,30 @@ static void msm_atomic_pending_work(struct work_struct *work) msm_atomic_async_commit(timer->kms, timer->crtc_idx); } -void msm_atomic_init_pending_timer(struct msm_pending_timer *timer, +int msm_atomic_init_pending_timer(struct msm_pending_timer *timer, struct msm_kms *kms, int crtc_idx) { timer->kms = kms; timer->crtc_idx = crtc_idx; hrtimer_init(&timer->timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS); timer->timer.function = msm_atomic_pending_timer; - INIT_WORK(&timer->work, msm_atomic_pending_work); + + timer->worker = kthread_create_worker(0, "atomic-worker-%d", crtc_idx); + if (IS_ERR(timer->worker)) { + int ret = PTR_ERR(timer->worker); + timer->worker = NULL; + return ret; + } + sched_set_fifo(timer->worker->task); + kthread_init_work(&timer->work, msm_atomic_pending_work); + + return 0; +} + +void msm_atomic_destroy_pending_timer(struct msm_pending_timer *timer) +{ + if (timer->worker) + kthread_destroy_worker(timer->worker); } static bool can_do_async(struct drm_atomic_state *state, diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h index b9dd8f8f4887..1a377128ee2c 100644 --- a/drivers/gpu/drm/msm/msm_drv.h +++ b/drivers/gpu/drm/msm/msm_drv.h @@ -228,8 +228,9 @@ struct msm_pending_timer; int msm_atomic_prepare_fb(struct drm_plane *plane, struct drm_plane_state *new_state); -void msm_atomic_init_pending_timer(struct msm_pending_timer *timer, +int msm_atomic_init_pending_timer(struct msm_pending_timer *timer, struct msm_kms *kms, int crtc_idx); +void msm_atomic_destroy_pending_timer(struct msm_pending_timer *timer); void msm_atomic_commit_tail(struct drm_atomic_state *state); struct drm_atomic_state *msm_atomic_state_alloc(struct drm_device *dev); void msm_atomic_state_clear(struct drm_atomic_state *state); diff --git a/drivers/gpu/drm/msm/msm_kms.h b/drivers/gpu/drm/msm/msm_kms.h index 602c0c7f300a..d8151a89e163 100644 --- a/drivers/gpu/drm/msm/msm_kms.h +++ b/drivers/gpu/drm/msm/msm_kms.h @@ -136,7 +136,8 @@ struct msm_kms; */ struct msm_pending_timer { struct hrtimer timer; - struct work_struct work; + struct kthread_work work; + struct kthread_worker *worker; struct msm_kms *kms; unsigned crtc_idx; }; @@ -163,21 +164,29 @@ struct msm_kms { static inline int msm_kms_init(struct msm_kms *kms, const struct msm_kms_funcs *funcs) { - unsigned i; + unsigned i, ret; for (i = 0; i < ARRAY_SIZE(kms->commit_lock); i++) mutex_init(&kms->commit_lock[i]); kms->funcs = funcs; - for (i = 0; i < ARRAY_SIZE(kms->pending_timers); i++) - msm_atomic_init_pending_timer(&kms->pending_timers[i], kms, i); + for (i = 0; i < ARRAY_SIZE(kms->pending_timers); i++) { + ret = msm_atomic_init_pending_timer(&kms->pending_timers[i], kms, i); + if (ret) { + return ret; + } + } return 0; } static inline void msm_kms_destroy(struct msm_kms *kms) { + unsigned i; + + for (i = 0; i < ARRAY_SIZE(kms->pending_timers); i++) + msm_atomic_destroy_pending_timer(&kms->pending_timers[i]); } struct msm_kms *mdp4_kms_init(struct drm_device *dev); -- cgit