On Tue, Jan 23, 2018 at 12:30:58AM -0800, John Stultz wrote:
> In trying to use the drm_hwcomposer on HiKey, I found things
> wouldn't initialize due to the following check in
> drm_atomic_crtc_check() failing:
>
> if (state->event && !state->active && !crtc->state->active) {
> DRM_DEBUG_ATOMIC("[CRTC:%d:%s] requesting event but off\n",
> crtc->base.id, crtc->name);
> return -EINVAL;
> }
I think the answer is in the comment directly above this code. Having an event
present while the crtc _stays_ off is the problem. So drm_hwc is requesting an
event (or providing a fence) for a crtc which it does not turn on. So I think
you should go back into hwc and find out how this situation arises.
AFAIK, requesting an event in a commit with both a modeset and plane update
should work.
Sean
>
> This case fails because the crtc_state hasn't been set to active
> yet.
>
> However, this trips on the first call to drm_atomic_commit(),
> where the drm_hwcomposer is trying to setup the initial mode.
>
> Digging further its seems the state->event value is set because
> before we get into handling the atomic mode, we call
> prepare_crtc_signaling(), which sees a fence ptr, and calls
> create_vblank_event().
>
> So to hack around this, I've added a check in
> prepare_crtc_signaling() to see if the crtc_state is active and
> if not, skip trying to create the vblank event.
>
> I suspect this isn't correct, but I'm a bit confused on what the
> right solution is. I was thinking the drm_hwcomposer was missing
> something to enable the display before calling
> drmModeAtomicCommit(), but as I look at the logic it seems that
> should be ok. I'm starting to suspect I only see this issue
> because I don't have the framebuffer console enabled, so the
> kernel has yet to initialize the crtc, and that's probably not
> commonly used.
>
> Any thoughts or feedback on a better approach to solving this
> issue would be greatly appreciated!
>
> Cc: Marissa Wall <marissaw@xxxxxxxxxx>
> Cc: Sean Paul <seanpaul@xxxxxxxxxx>
> Cc: Dmitry Shmidt <dimitrysh@xxxxxxxxxx>
> Cc: Matt Szczesiak <matt.szczesiak@xxxxxxx>
> Cc: Liviu Dudau <Liviu.Dudau@xxxxxxx>
> Cc: David Hanna <david.hanna11@xxxxxxxxx>
> Cc: Rob Herring <rob.herring@xxxxxxxxxx>
> Cc: Sumit Semwal <sumit.semwal@xxxxxxxxxx>
> Cc: Robert Foss <robert.foss@xxxxxxxxxxxxx>
> Cc: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxx>
> Cc: Rob Clark <robdclark@xxxxxxxxx>
> Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx>
> ---
> drivers/gpu/drm/drm_atomic.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> index c2da558..e6404b2 100644
> --- a/drivers/gpu/drm/drm_atomic.c
> +++ b/drivers/gpu/drm/drm_atomic.c
> @@ -2072,6 +2072,9 @@ static int prepare_crtc_signaling(struct drm_device *dev,
> for_each_new_crtc_in_state(state, crtc, crtc_state, i) {
> s32 __user *fence_ptr;
>
> + if (!crtc_state->active)
> + continue;
> +
> fence_ptr = get_out_fence_for_crtc(crtc_state->state, crtc);
>
> if (arg->flags & DRM_MODE_PAGE_FLIP_EVENT || fence_ptr) {
> --
> 2.7.4
>
--
Sean Paul, Software Engineer, Google / Chromium OS
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