Hello, On 12/13/18 7:01 AM, Daniel Vetter wrote: > On Thu, Dec 13, 2018 at 04:43:57PM +0900, Tomasz Figa wrote: >> Hi Helen, >> >> On Sat, Nov 24, 2018 at 6:54 AM Helen Koike <helen.ko...@collabora.com> >> wrote: >>> >>> This flag tells core to jump ahead the queued update if the conditions >>> in drm_atomic_async_check() are met. That means we are only able to do an >>> async update if no modeset is pending and update for the same plane is >>> not queued. >> >> First of all, thanks for the patch. Please see my comments below. >> >> If the description above applies (and AFAICT that's what the existing >> code does indeed), then this doesn't sound like "amend" to me. It >> sounds exactly as the kernel code calls it - "async update" or perhaps >> "instantaneous commit" could better describe it?
There is an error in this patch (please, see below). Async should fail if there is no pending commit, at least is what I understand from the discussion at https://patchwork.freedesktop.org/patch/243088/ >> >>> >>> It uses the already in place infrastructure for async updates. >>> >>> It is useful for cursor updates and async PageFlips over the atomic >>> ioctl, otherwise in some cases updates may be delayed to the point the >>> user will notice it. Note that for now it's only enabled for cursor >>> planes. >>> >>> DRM_MODE_ATOMIC_AMEND should be passed to the Atomic IOCTL to use this >>> feature. >>> >>> Signed-off-by: Gustavo Padovan <gustavo.pado...@collabora.com> >>> Signed-off-by: Enric Balletbo i Serra <enric.balle...@collabora.com> >>> [updated for upstream] >>> Signed-off-by: Helen Koike <helen.ko...@collabora.com> >>> --- >>> Hi, >>> >>> This is the second attempt to introduce the new ATOMIC_AMEND flag for atomic >>> operations, see the commit message for a more detailed description. >>> >>> This was tested using a small program that exercises the uAPI for easy >>> sanity testing. The program was created by Alexandros and modified by >>> Enric to test the capability flag [2]. >>> >>> To test, just build the program and use the --atomic flag to use the cursor >>> plane with the ATOMIC_AMEND flag. E.g. >>> >>> drm_cursor --atomic >>> >>> The test worked on a rockchip Ficus v1.1 board on top of mainline plus >>> the patch to update cursors asynchronously through atomic for the >>> drm/rockchip driver plus the DRM_CAP_ASYNC_UPDATE patch. >>> >>> Alexandros also did a proof-of-concept to use this flag and draw cursors >>> using atomic if possible on ozone [1]. >>> >>> Thanks >>> Helen >>> >>> [1] https://chromium-review.googlesource.com/c/chromium/src/+/1092711 >>> [2] >>> https://gitlab.collabora.com/eballetbo/drm-cursor/commits/async-capability >>> >>> >>> Changes in v2: >>> - rebase tree >>> - do not fall back to a non-async update if if there isn't any >>> pending commit to amend >>> >>> Changes in v1: >>> - https://patchwork.freedesktop.org/patch/243088/ >>> - Only enable it if userspace requests it. >>> - Only allow async update for cursor type planes. >>> - Rename ASYNC_UPDATE for ATOMIC_AMEND. >>> >>> drivers/gpu/drm/drm_atomic_helper.c | 6 +++++- >>> drivers/gpu/drm/drm_atomic_uapi.c | 6 ++++++ >>> include/uapi/drm/drm_mode.h | 4 +++- >>> 3 files changed, 14 insertions(+), 2 deletions(-) >>> >>> diff --git a/drivers/gpu/drm/drm_atomic_helper.c >>> b/drivers/gpu/drm/drm_atomic_helper.c >>> index 269f1a74de38..333190c6a0a4 100644 >>> --- a/drivers/gpu/drm/drm_atomic_helper.c >>> +++ b/drivers/gpu/drm/drm_atomic_helper.c >>> @@ -934,7 +934,7 @@ int drm_atomic_helper_check(struct drm_device *dev, >>> if (ret) >>> return ret; >>> >>> - if (state->legacy_cursor_update) >>> + if (state->async_update || state->legacy_cursor_update) >>> state->async_update = !drm_atomic_helper_async_check(dev, >>> state); I just realized this is wrong, drm_atomic_helper_async_check() should return error if there is a pending old_plane_state->commit (this v2 patch is not doing this, but v1 was), if drm_atomic_helper_async_check() returned because of it, then we should return error here to scale this failure to userspace. Make sense? Tomasz, do you agree? >>> >>> return ret; >>> @@ -1602,6 +1602,10 @@ int drm_atomic_helper_async_check(struct drm_device >>> *dev, >>> if (new_plane_state->fence) >>> return -EINVAL; >>> >>> + /* Only allow async update for cursor type planes. */ >>> + if (plane->type != DRM_PLANE_TYPE_CURSOR) >>> + return -EINVAL; >>> + >> >> So the existing upstream code already allowed this for any planes and >> we're restricting this to cursor planes only. Is this expected? No >> potential users that already started using this for other plane types? > > The backend supports it for anything right now (if the driver implements > it, that is). We do expose it through the legacy cursor api, and the > legacy page_flip api, but not through atomic itself. It also has the > problem that the not all drivers who support the async legacy cursor mode > in atomic use this new infrastructure, so there's a few problems. Plus > semantics are very ill-defined (we'd definitely need igt testcases for > this stuff, especially all the new combinations with events, fences, ...). > > I think what we'd need here to make sure we're not digging an uapi hole: > > 1. Entirely remove the legacy_cursor_update hack. There's some patches > floating around, but would need to be polished. > > 2. Make sure all drivers supporting legacy async cursor updates do through > the async_plane update infrastructure. > > 3. Get the async plane update stuff merged for amdgpu. Iirc that's still > stuck somewhere (but I'm not 100% sure what exactly they're doing). > > 4. Pile of igt testcases for all the new corner cases exposing this in > atomic opens up. Many cases we might want to simply reject it. > > 5. Userspace. Big one I have is whether we need a flag like ALLOW_MODESET, > since the current code transparently falls back to vblank-synced updates > if async updates aren't available. > > tldr; lots of work. Also maybe: > > 0. Dump this todo into Documentation/gpu/todo.rst so it won't get lost. > > Cheers, Daniel > Thanks Daniel for pointing those out, I'll start to take a look on them. > >> >> Best regards, >> Tomasz >> _______________________________________________ >> dri-devel mailing list >> dri-devel@lists.freedesktop.org >> https://lists.freedesktop.org/mailman/listinfo/dri-devel > Thanks Helen _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
