On Tue, Jul 07, 2020 at 10:12:11PM +0200, Daniel Vetter wrote:
> Like the helpers, nothing special. Well except not, because we the
> critical section extends until after hw_done(), since that's the last
> thing which could hold up a subsequent atomic commit. That means the
> wait_for_flip_done is included, but that's not a problem, we're
> allowed to call dma_fence_wait() from signalling critical sections.
> Even on our own fence (which this does), it's just a bit confusing.
> But in a way those last 2 function calls are already part of the fence
> signalling critical section for the next atomic commit.
>
> Reading this I'm wondering why komeda waits for flip_done() before
> calling hw_done(), which is a bit backwards (but hey hw can be
> special). Might be good to throw a comment in there that explains why,
> because the original commit that added this just doesn't.
Hi Daniel:
It's a typo, thank you for pointing this out, and I'll give a fix after
this series have been merged.
for this patch
Reviewed-by: James Qian Wang <james.qian.wang@xxxxxxx>
> Cc: "James (Qian) Wang" <james.qian.wang@xxxxxxx>
> Cc: Liviu Dudau <liviu.dudau@xxxxxxx>
> Cc: Mihail Atanassov <mihail.atanassov@xxxxxxx>
> Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx>
> ---
> drivers/gpu/drm/arm/display/komeda/komeda_kms.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/gpu/drm/arm/display/komeda/komeda_kms.c b/drivers/gpu/drm/arm/display/komeda/komeda_kms.c
> index 1f6682032ca4..cc5b5915bc5e 100644
> --- a/drivers/gpu/drm/arm/display/komeda/komeda_kms.c
> +++ b/drivers/gpu/drm/arm/display/komeda/komeda_kms.c
> @@ -73,6 +73,7 @@ static struct drm_driver komeda_kms_driver = {
> static void komeda_kms_commit_tail(struct drm_atomic_state *old_state)
> {
> struct drm_device *dev = old_state->dev;
> + bool fence_cookie = dma_fence_begin_signalling();
>
> drm_atomic_helper_commit_modeset_disables(dev, old_state);
>
> @@ -85,6 +86,8 @@ static void komeda_kms_commit_tail(struct drm_atomic_state *old_state)
>
> drm_atomic_helper_commit_hw_done(old_state);
>
> + dma_fence_end_signalling(fence_cookie);
> +
> drm_atomic_helper_cleanup_planes(dev, old_state);
> }
>
> --
> 2.27.0
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