From: Tomi Valkeinen Date: Fri, 5 Sep 2025 13:58:07 +0000 (+0300) Subject: drm/tidss: Set vblank (event) time at crtc_atomic_enable X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=8cde1c9b19723cd699c203d48378db201dd64db5;p=thirdparty%2Fkernel%2Flinux.git drm/tidss: Set vblank (event) time at crtc_atomic_enable It was reported that Weston stops at an assert, which checks that the page flip event timestamp is the same or newer than the previous timestamp: weston_output_finish_frame: Assertion `timespec_sub_to_nsec(stamp, &output->frame_time) >= 0' failed. With manual tests, I can see that when I enable the CRTC, I get a page flip event with a timestamp of 0. Tracking this down led to drm_reset_vblank_timestamp() which does "t_vblank = 0" if "high-precision query" is not available. TI DSS does not have any hardware timestamping, and thus the default ktime_get() is used in the DRM framework to get the vblank timestamp, and ktime_get() is not "high precision" here. It is not quite clear why the framework behaves this way, but I assume the idea is that drm_crtc_vblank_on(), which calls drm_reset_vblank_timestamp(), can be called at any time, and thus ktime_get() wouldn't give a good timestamp. And, the idea is that the driver would wait until next vblank after the CRTC enable, and then we could get a good timestamp. This is hinted in the comment: "reinitialize delayed at next vblank interrupt and assign 0 for now". I think that makes sense. However, when we enable the CRTC in TI DSS, i.e. we write the enable bit to the hardware, that's the exact moment when the "vblank cycle" starts. It is the zero point in the cycle, and thus ktime_get() would give a good timestamp. I am not sure if this is applicable to other hardware, and if so, how should it be solved in the framework. So, let's fix this in the tidss driver at least for now. This patch updates the vblank->time manually to ktime_get() just before sending the vblank event, and we enable the crtc just before calling ktime_get(). To get even more exact timing, the dispc_vp_enable() is moved inside the event_lock spinlock. With this, we get a proper timestamp for the page flip event from enabling the CRTC, and Weston is happy. Reviewed-by: Devarsh Thakkar Link: https://patch.msgid.link/20250905-tidss-fix-timestamp-v1-2-c2aedf31e2c9@ideasonboard.com Signed-off-by: Tomi Valkeinen Closes: https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1553964/processor-sdk-am62x-weston-fails-to-wake-from-idle-time-sleep-restarts-after-sigterm Closes: https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1416342/am625-am625-doesn-t-wake-up-from-standy-when-idle-time-is-configured-in-weston-ini --- diff --git a/drivers/gpu/drm/tidss/tidss_crtc.c b/drivers/gpu/drm/tidss/tidss_crtc.c index 11807963c941c..411b1a25e29c6 100644 --- a/drivers/gpu/drm/tidss/tidss_crtc.c +++ b/drivers/gpu/drm/tidss/tidss_crtc.c @@ -243,11 +243,16 @@ static void tidss_crtc_atomic_enable(struct drm_crtc *crtc, dispc_vp_prepare(tidss->dispc, tcrtc->hw_videoport, crtc->state); - dispc_vp_enable(tidss->dispc, tcrtc->hw_videoport); - spin_lock_irqsave(&ddev->event_lock, flags); + dispc_vp_enable(tidss->dispc, tcrtc->hw_videoport); + if (crtc->state->event) { + unsigned int pipe = drm_crtc_index(crtc); + struct drm_vblank_crtc *vblank = &ddev->vblank[pipe]; + + vblank->time = ktime_get(); + drm_crtc_send_vblank_event(crtc, crtc->state->event); crtc->state->event = NULL; }