From 1fab978a9585cc7fea483583bc1c76e9e48e4f35 Mon Sep 17 00:00:00 2001 From: Sultan Alsawaf Date: Sun, 22 Jan 2023 23:31:52 -0800 Subject: present: Fix inaccurate PresentCompleteNotify timing for TearFree The timing of PresentCompleteNotify events is inaccurate when a driver uses TearFree because there's no way to know exactly when a presentation will appear on the display without receiving a notification directly from the driver indicating that the TearFree flip containing a presentation's pixmap is actually visible on the display. To fix the inaccurate PresentCompleteNotify timing, make use of the new assumption that drivers which export TearFree permit a NULL pixmap to be passed to their flip callback in order to make a presentation track the exact TearFree flip responsible for rendering it onto the display. Signed-off-by: Sultan Alsawaf Acked-by: Martin Roukala --- present/present_scmd.c | 58 +++++++++++++++++++++++++++++++++----------------- 1 file changed, 38 insertions(+), 20 deletions(-) diff --git a/present/present_scmd.c b/present/present_scmd.c index 59feb001b..d378f0016 100644 --- a/present/present_scmd.c +++ b/present/present_scmd.c @@ -646,30 +646,48 @@ present_execute(present_vblank_ptr vblank, uint64_t ust, uint64_t crtc_msc) present_execute_copy(vblank, crtc_msc); - /* The presentation will be visible at the next vblank with TearFree, so - * the PresentComplete notification needs to be sent at the next vblank. - * If TearFree is already flipping then the presentation will be visible - * at the *next* next vblank. + /* With TearFree, there's no way to tell exactly when the presentation + * will be visible except by waiting for a notification from the kernel + * driver indicating that the page flip is complete. This is because the + * CRTC's MSC can change while the target MSC is calculated and even + * while the page flip IOCTL is sent to the kernel due to scheduling + * delays and/or unfortunate timing. Even worse, a page flip isn't + * actually guaranteed to be finished after one vblank; it may be + * several MSCs until a flip actually finishes depending on delays and + * load in hardware. + * + * So, to get a notification from the driver with TearFree active, the + * driver expects a present_flip() call with a NULL pixmap to indicate + * that this is a fake flip for a pixmap that's already been copied to + * the primary scanout, which will then be flipped by TearFree. TearFree + * will then send a notification once the flip containing this pixmap is + * complete. + * + * If the fake flip attempt fails, then fall back to just enqueuing a + * vblank event targeting the next MSC. */ - if (!vblank->queued) { + if (!vblank->queued && + vblank->reason >= PRESENT_FLIP_REASON_DRIVER_TEARFREE) { uint64_t completion_msc = crtc_msc + 1; - switch (vblank->reason) { - case PRESENT_FLIP_REASON_DRIVER_TEARFREE_FLIPPING: - if (vblank->exec_msc < crtc_msc) + /* If TearFree is already flipping then the presentation will be + * visible at the *next* next vblank. This calculation only matters + * for the vblank event fallback. + */ + if (vblank->reason == PRESENT_FLIP_REASON_DRIVER_TEARFREE_FLIPPING && + vblank->exec_msc < crtc_msc) completion_msc++; - case PRESENT_FLIP_REASON_DRIVER_TEARFREE: - if (Success == screen_priv->queue_vblank(screen, - window, - vblank->crtc, - vblank->event_id, - completion_msc)) { - /* Ensure present_execute_post() runs at the next MSC */ - vblank->exec_msc = vblank->target_msc; - vblank->queued = TRUE; - } - default: - break; + + /* Try the fake flip first and then fall back to a vblank event */ + if (present_flip(vblank->crtc, vblank->event_id, 0, NULL, TRUE) || + Success == screen_priv->queue_vblank(screen, + window, + vblank->crtc, + vblank->event_id, + completion_msc)) { + /* Ensure present_execute_post() runs at the next execution */ + vblank->exec_msc = vblank->target_msc; + vblank->queued = TRUE; } } -- cgit v1.2.1