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SubjectRe: [PATCH v2 RESEND] drm/komeda: Workaround for broken FLIP_COMPLETE timestamps
Date
On Tue, Oct 01, 2019 at 02:21:40PM +0000, 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 <daniel@ffwll.ch>
> Cc: Liviu Dudau <Liviu.Dudau@arm.com>
> Signed-off-by: Mihail Atanassov <mihail.atanassov@arm.com>
> Reviewed-by: James Qian Wang (Arm Technology China) <james.qian.wang@arm.com>

Pushed to drm-misc-next f59769c52cd7d158df53487ec2936f5592073340

Thanks,
Ayan
> ---
> 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 9ca5dbfd0723..75263d8cd0bd 100644
> --- a/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
> +++ b/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
> @@ -249,6 +249,7 @@ komeda_crtc_atomic_enable(struct drm_crtc *crtc,
> {
> komeda_crtc_prepare(to_kcrtc(crtc));
> drm_crtc_vblank_on(crtc);
> + WARN_ON(drm_crtc_vblank_get(crtc));
> komeda_crtc_do_flush(crtc, old);
> }
>
> @@ -341,6 +342,7 @@ 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);
> }
> --
> 2.23.0
>
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

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