[Freedreno] [PATCH 2/2] drm/msm: make msm_disp_state transient data struct
Dmitry Baryshkov
dmitry.baryshkov at linaro.org
Mon Apr 26 22:14:37 UTC 2021
On Tue, 27 Apr 2021 at 01:03, <abhinavk at codeaurora.org> wrote:
>
> On 2021-04-26 14:23, Dmitry Baryshkov wrote:
> > On 26/04/2021 23:50, abhinavk at codeaurora.org wrote:
> >> On 2021-04-25 09:08, Dmitry Baryshkov wrote:
> >>> Instead of allocating snapshotting structure at the driver probe time
> >>> and later handling concurrent access, actual state, etc, make
> >>> msm_disp_state transient struct. Allocate one when snapshotting
> >>> happens
> >>> and free it after coredump data is read by userspace.
> >>
> >> the purpose of the mutex is that when there are two coredumps being
> >> triggered
> >> by two consecutive errors, we want to make sure that till one coredump
> >> is completely
> >> read and/or processed, we do not allow triggering of another one as we
> >> want to capture
> >> the accurate hardware/software state.
> >>
> >> So moving disp_state out of kms might be okay and just allocated it
> >> when actually capturing the state
> >> but we will need the mutex and some sort of pending flag in my
> >> opinion.
> >
> > I'll return the mutex to the kms struct, so that we won't start
> > another snapshot untill previous one is complete.
>
> I think mutex should remain as part of snapshot so that they go
> together. Since this mutex is not used
> by any other module, I thought its better to keep it there.
I don't think so: we will serialize access to the snapshot, but not
dumping between snapshots. Note, that your code also serializes
writing to snapshot, not reading from it.
With disp_state being allocated on demand we do not have to protect
its contents (since it is not available before registration using
dev_codedumpm).
I thought that you wanted to be sure that one snapshot is fully
captured before next error triggers the next snapshot. And for this
we'd need 'global' mutex (in kms).
> > Concerning the pending flag, I think it is also handled by the
> > coredump code: dev_coredumpm() will not create another device if there
> > is one already associated with the device being dumped. I should
> > probably mention this in the commit message.
>
> Thats a good point, I checked that now as well but I still think we need
> this flag because
> it also makes sure devcoredump is taken and read together within our
> driver itself instead of relying
> on the devcoredump. Its not a strong preference.
>
> But if you would like to go ahead with this, might have to retest its
> robustness.
> With the older logic how i verified this was that I relaxed the underrun
> cnt check in this patch
> ( https://patchwork.freedesktop.org/patch/429112/?series=89181&rev=1 )
> here and simulated an error:
>
> @@ -1336,6 +1337,11 @@ static void dpu_encoder_underrun_callback(struct
> drm_encoder *drm_enc,
>
> DPU_ATRACE_BEGIN("encoder_underrun_callback");
> atomic_inc(&phy_enc->underrun_cnt);
> +
> + /* trigger dump only on the first underrun */
> + if (atomic_read(&phy_enc->underrun_cnt) == 1)
> + msm_disp_snapshot_state(drm_enc->dev);
> +
>
> And verified that across various underrun interrupts, the devcoredump is
> stable.
I'll try testing it this way, thank you for the pointer!
>
> >
> > If you agree with this, I'll send v2 then (also adding plls dumping).
> Looking fwd to seeing the pll dumping, that will be a great addition to
> this.
> >
> >>
> >>>
> >>> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov at linaro.org>
> >>> ---
> >>> drivers/gpu/drm/msm/disp/msm_disp_snapshot.c | 87
> >>> ++++---------------
> >>> drivers/gpu/drm/msm/disp/msm_disp_snapshot.h | 13 +--
> >>> .../gpu/drm/msm/disp/msm_disp_snapshot_util.c | 5 +-
> >>> drivers/gpu/drm/msm/msm_kms.h | 5 +-
> >>> 4 files changed, 28 insertions(+), 82 deletions(-)
> >>>
> >>> diff --git a/drivers/gpu/drm/msm/disp/msm_disp_snapshot.c
> >>> b/drivers/gpu/drm/msm/disp/msm_disp_snapshot.c
> >>> index 70fd5a1fe13e..371358893716 100644
> >>> --- a/drivers/gpu/drm/msm/disp/msm_disp_snapshot.c
> >>> +++ b/drivers/gpu/drm/msm/disp/msm_disp_snapshot.c
> >>> @@ -7,8 +7,7 @@
> >>>
> >>> #include "msm_disp_snapshot.h"
> >>>
> >>> -#ifdef CONFIG_DEV_COREDUMP
> >>> -static ssize_t disp_devcoredump_read(char *buffer, loff_t offset,
> >>> +static ssize_t __maybe_unused disp_devcoredump_read(char *buffer,
> >>> loff_t offset,
> >>> size_t count, void *data, size_t datalen)
> >>> {
> >>> struct drm_print_iterator iter;
> >>> @@ -29,24 +28,21 @@ static ssize_t disp_devcoredump_read(char
> >>> *buffer,
> >>> loff_t offset,
> >>> return count - iter.remain;
> >>> }
> >>>
> >>> -static void disp_devcoredump_free(void *data)
> >>> +static void _msm_disp_snapshot_work(struct kthread_work *work)
> >>> {
> >>> + struct msm_kms *msm_kms = container_of(work, struct msm_kms,
> >>> dump_work);
> >>> + struct drm_device *drm_dev = msm_kms->dev;
> >>> struct msm_disp_state *disp_state;
> >>> + struct drm_printer p;
> >>>
> >>> - disp_state = data;
> >>> -
> >>> - msm_disp_state_free(disp_state);
> >>> -
> >>> - disp_state->coredump_pending = false;
> >>> -}
> >>> -#endif /* CONFIG_DEV_COREDUMP */
> >>> + disp_state = kzalloc(sizeof(struct msm_disp_state), GFP_KERNEL);
> >>> + if (!disp_state)
> >>> + return;
> >>>
> >>> -static void _msm_disp_snapshot_work(struct kthread_work *work)
> >>> -{
> >>> - struct msm_disp_state *disp_state = container_of(work, struct
> >>> msm_disp_state, dump_work);
> >>> - struct drm_printer p;
> >>> + disp_state->dev = drm_dev->dev;
> >>> + disp_state->drm_dev = drm_dev;
> >>>
> >>> - mutex_lock(&disp_state->mutex);
> >>> + INIT_LIST_HEAD(&disp_state->blocks);
> >>>
> >>> msm_disp_snapshot_capture_state(disp_state);
> >>>
> >>> @@ -55,26 +51,15 @@ static void _msm_disp_snapshot_work(struct
> >>> kthread_work *work)
> >>> msm_disp_state_print(disp_state, &p);
> >>> }
> >>>
> >>> - /*
> >>> - * if devcoredump is not defined free the state immediately
> >>> - * otherwise it will be freed in the free handler.
> >>> - */
> >>> -#ifdef CONFIG_DEV_COREDUMP
> >>> + /* If COREDUMP is disabled, the stub will call the free
> >>> function. */
> >> This is a good cleanup, I just checked that the free() is called even
> >> if the config is not enabled
> >>> dev_coredumpm(disp_state->dev, THIS_MODULE, disp_state, 0,
> >>> GFP_KERNEL,
> >>> - disp_devcoredump_read, disp_devcoredump_free);
> >>> - disp_state->coredump_pending = true;
> >>> -#else
> >>> - msm_disp_state_free(disp_state);
> >>> -#endif
> >>> -
> >>> - mutex_unlock(&disp_state->mutex);
> >>> + disp_devcoredump_read, msm_disp_state_free);
> >>> }
> >>>
> >>> void msm_disp_snapshot_state(struct drm_device *drm_dev)
> >>> {
> >>> struct msm_drm_private *priv;
> >>> struct msm_kms *kms;
> >>> - struct msm_disp_state *disp_state;
> >>>
> >>> if (!drm_dev) {
> >>> DRM_ERROR("invalid params\n");
> >>> @@ -83,30 +68,13 @@ void msm_disp_snapshot_state(struct drm_device
> >>> *drm_dev)
> >>>
> >>> priv = drm_dev->dev_private;
> >>> kms = priv->kms;
> >>> - disp_state = kms->disp_state;
> >>> -
> >>> - if (!disp_state) {
> >>> - DRM_ERROR("invalid params\n");
> >>> - return;
> >>> - }
> >>> -
> >>> - /*
> >>> - * if there is a coredump pending return immediately till dump
> >>> - * if read by userspace or timeout happens
> >>> - */
> >>> - if (disp_state->coredump_pending) {
> >>> - DRM_DEBUG("coredump is pending read\n");
> >>> - return;
> >>> - }
> >>>
> >>> - kthread_queue_work(disp_state->dump_worker,
> >>> - &disp_state->dump_work);
> >>> + kthread_queue_work(kms->dump_worker, &kms->dump_work);
> >>> }
> >>>
> >>> int msm_disp_snapshot_init(struct drm_device *drm_dev)
> >>> {
> >>> struct msm_drm_private *priv;
> >>> - struct msm_disp_state *disp_state;
> >>> struct msm_kms *kms;
> >>>
> >>> if (!drm_dev) {
> >>> @@ -117,22 +85,11 @@ int msm_disp_snapshot_init(struct drm_device
> >>> *drm_dev)
> >>> priv = drm_dev->dev_private;
> >>> kms = priv->kms;
> >>>
> >>> - disp_state = devm_kzalloc(drm_dev->dev, sizeof(struct
> >>> msm_disp_state), GFP_KERNEL);
> >>> -
> >>> - mutex_init(&disp_state->mutex);
> >>> -
> >>> - disp_state->dev = drm_dev->dev;
> >>> - disp_state->drm_dev = drm_dev;
> >>> -
> >>> - INIT_LIST_HEAD(&disp_state->blocks);
> >>> -
> >>> - disp_state->dump_worker = kthread_create_worker(0, "%s",
> >>> "disp_snapshot");
> >>> - if (IS_ERR(disp_state->dump_worker))
> >>> + kms->dump_worker = kthread_create_worker(0, "%s",
> >>> "disp_snapshot");
> >>> + if (IS_ERR(kms->dump_worker))
> >>> DRM_ERROR("failed to create disp state task\n");
> >>>
> >>> - kthread_init_work(&disp_state->dump_work,
> >>> _msm_disp_snapshot_work);
> >>> -
> >>> - kms->disp_state = disp_state;
> >>> + kthread_init_work(&kms->dump_work, _msm_disp_snapshot_work);
> >>>
> >>> return 0;
> >>> }
> >>> @@ -141,7 +98,6 @@ void msm_disp_snapshot_destroy(struct drm_device
> >>> *drm_dev)
> >>> {
> >>> struct msm_kms *kms;
> >>> struct msm_drm_private *priv;
> >>> - struct msm_disp_state *disp_state;
> >>>
> >>> if (!drm_dev) {
> >>> DRM_ERROR("invalid params\n");
> >>> @@ -150,12 +106,7 @@ void msm_disp_snapshot_destroy(struct drm_device
> >>> *drm_dev)
> >>>
> >>> priv = drm_dev->dev_private;
> >>> kms = priv->kms;
> >>> - disp_state = kms->disp_state;
> >>> -
> >>> - if (disp_state->dump_worker)
> >>> - kthread_destroy_worker(disp_state->dump_worker);
> >>> -
> >>> - list_del(&disp_state->blocks);
> >>>
> >>> - mutex_destroy(&disp_state->mutex);
> >>> + if (kms->dump_worker)
> >>> + kthread_destroy_worker(kms->dump_worker);
> >>> }
> >>> diff --git a/drivers/gpu/drm/msm/disp/msm_disp_snapshot.h
> >>> b/drivers/gpu/drm/msm/disp/msm_disp_snapshot.h
> >>> index 32f52799a1ba..c6174a366095 100644
> >>> --- a/drivers/gpu/drm/msm/disp/msm_disp_snapshot.h
> >>> +++ b/drivers/gpu/drm/msm/disp/msm_disp_snapshot.h
> >>> @@ -41,26 +41,17 @@
> >>> * struct msm_disp_state - structure to store current dpu state
> >>> * @dev: device pointer
> >>> * @drm_dev: drm device pointer
> >>> - * @mutex: mutex to serialize access to serialze dumps, debugfs
> >>> access
> >>> - * @coredump_pending: coredump is pending read from userspace
> >>> * @atomic_state: atomic state duplicated at the time of the error
> >>> - * @dump_worker: kworker thread which runs the dump work
> >>> - * @dump_work: kwork which dumps the registers and drm state
> >>> * @timestamp: timestamp at which the coredump was captured
> >>> */
> >>> struct msm_disp_state {
> >>> struct device *dev;
> >>> struct drm_device *drm_dev;
> >>> - struct mutex mutex;
> >>> -
> >>> - bool coredump_pending;
> >>>
> >>> struct list_head blocks;
> >>>
> >>> struct drm_atomic_state *atomic_state;
> >>>
> >>> - struct kthread_worker *dump_worker;
> >>> - struct kthread_work dump_work;
> >>> ktime_t timestamp;
> >>> };
> >>>
> >>> @@ -123,11 +114,11 @@ void msm_disp_snapshot_capture_state(struct
> >>> msm_disp_state *disp_state);
> >>>
> >>> /**
> >>> * msm_disp_state_free - free the memory after the coredump has been
> >>> read
> >>> - * @disp_state: handle to struct msm_disp_state
> >>> + * @data: handle to struct msm_disp_state
> >>>
> >>> * Returns: none
> >>> */
> >>> -void msm_disp_state_free(struct msm_disp_state *disp_state);
> >>> +void msm_disp_state_free(void *data);
> >>>
> >>> /**
> >>> * msm_disp_snapshot_add_block - add a hardware block with its
> >>> register dump
> >>> diff --git a/drivers/gpu/drm/msm/disp/msm_disp_snapshot_util.c
> >>> b/drivers/gpu/drm/msm/disp/msm_disp_snapshot_util.c
> >>> index ca6632550337..cabe15190ec1 100644
> >>> --- a/drivers/gpu/drm/msm/disp/msm_disp_snapshot_util.c
> >>> +++ b/drivers/gpu/drm/msm/disp/msm_disp_snapshot_util.c
> >>> @@ -142,8 +142,9 @@ void msm_disp_snapshot_capture_state(struct
> >>> msm_disp_state *disp_state)
> >>> msm_disp_capture_atomic_state(disp_state);
> >>> }
> >>>
> >>> -void msm_disp_state_free(struct msm_disp_state *disp_state)
> >>> +void msm_disp_state_free(void *data)
> >>> {
> >>> + struct msm_disp_state *disp_state = data;
> >>> struct msm_disp_state_block *block, *tmp;
> >>>
> >>> if (disp_state->atomic_state) {
> >>> @@ -156,6 +157,8 @@ void msm_disp_state_free(struct msm_disp_state
> >>> *disp_state)
> >>> kfree(block->state);
> >>> kfree(block);
> >>> }
> >>> +
> >>> + kfree(disp_state);
> >>> }
> >>>
> >>> void msm_disp_snapshot_add_block(struct msm_disp_state *disp_state,
> >>> u32 len,
> >>> diff --git a/drivers/gpu/drm/msm/msm_kms.h
> >>> b/drivers/gpu/drm/msm/msm_kms.h
> >>> index 146dcab123f4..529b9dacf7ca 100644
> >>> --- a/drivers/gpu/drm/msm/msm_kms.h
> >>> +++ b/drivers/gpu/drm/msm/msm_kms.h
> >>> @@ -156,8 +156,9 @@ struct msm_kms {
> >>> /* mapper-id used to request GEM buffer mapped for scanout: */
> >>> struct msm_gem_address_space *aspace;
> >>>
> >>> - /* handle to disp snapshot state */
> >>> - struct msm_disp_state *disp_state;
> >>> + /* disp snapshot support */
> >>> + struct kthread_worker *dump_worker;
> >>> + struct kthread_work dump_work;
> >>>
> >>> /*
> >>> * For async commit, where ->flush_commit() and later happens
--
With best wishes
Dmitry
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