On Thu, Dec 13, 2018 at 11:35:33PM -0200, Helen Koike wrote: > 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.koike@xxxxxxxxxxxxx> 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/ Hm, that's not really my takeaway from that discussion. There's lots of open issues with this uapi (too many real-world corner cases that aren't thought through yet), but that conclusion I didn't find anywhere ... -Daniel > > >> > >>> > >>> 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.padovan@xxxxxxxxxxxxx> > >>> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@xxxxxxxxxxxxx> > >>> [updated for upstream] > >>> Signed-off-by: Helen Koike <helen.koike@xxxxxxxxxxxxx> > >>> --- > >>> 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@xxxxxxxxxxxxxxxxxxxxx > >> https://lists.freedesktop.org/mailman/listinfo/dri-devel > > > > > Thanks > Helen > _______________________________________________ > dri-devel mailing list > dri-devel@xxxxxxxxxxxxxxxxxxxxx > https://lists.freedesktop.org/mailman/listinfo/dri-devel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
