On Mon, Sep 23, 2019 at 10:10:26AM +, Mihail Atanassov wrote:
> When initially turning a crtc on, drm_reset_vblank_timestamp will
> set the vblank timestamp to 0 for any driver that doesn't provide
> a ->get_vblank_timestamp() hook.
>
> Unfortunately, the FLIP_COMPLETE event depends on that timestamp,
> and the only way to regenerate a valid one is to have vblank
> interrupts enabled and have a valid in-ISR call to
> drm_crtc_handle_vblank.
>
> Additionally, if the user doesn't request vblanks but _does_ request
> FLIP_COMPLETE events, we still don't have a good timestamp: it'll be the
> same stamp as the last vblank one.
>
> Work around the issue by always enabling vblanks when the CRTC is on.
> Reducing the amount of time that PL0 has to be unmasked would be nice to
> fix at a later time.
>
> Changes since v1 [https://patchwork.freedesktop.org/patch/331727/]:
> - moved drm_crtc_vblank_put call to the ->atomic_disable() hook
>
> Cc: Daniel Vetter
> Cc: Liviu Dudau
> Signed-off-by: Mihail Atanassov
> ---
> drivers/gpu/drm/arm/display/komeda/komeda_crtc.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
> b/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
> index 34bc73ca18bc..d06679afb228 100644
> --- a/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
> +++ b/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
> @@ -489,6 +489,7 @@ komeda_crtc_atomic_enable(struct drm_crtc *crtc,
> pm_runtime_get_sync(crtc->dev->dev);
> komeda_crtc_prepare(to_kcrtc(crtc));
> drm_crtc_vblank_on(crtc);
> + WARN_ON(drm_crtc_vblank_get(crtc));
> komeda_crtc_do_flush(crtc, old);
> }
>
> @@ -581,6 +582,7 @@ komeda_crtc_atomic_disable(struct drm_crtc *crtc,
> komeda_crtc_flush_and_wait_for_flip_done(kcrtc, disable_done);
> }
>
> + drm_crtc_vblank_put(crtc);
> drm_crtc_vblank_off(crtc);
> komeda_crtc_unprepare(kcrtc);
> pm_runtime_put(crtc->dev->dev);
Looks good to me.
Reviewed-by: James Qian Wang (Arm Technology China)
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