[WHY] The out fence was signalled on the first vblank after arming, before the DMA finished copying, and the old code worked around this with an mdelay() in the IRQ handler.
[HOW] Hold a vblank reference while writeback is pending and signal the out fence on the second vblank instead of using mdelay(). Add amdgpu_dm_crtc_complete_writeback() to finish and clean up writeback from both the IRQ and teardown paths. This can be verified by running IGT's kms_writeback 20 times without timeout errors. Assisted-by: Copilot:Claude-Opus-4.8 Signed-off-by: Alex Hung <[email protected]> --- drivers/gpu/drm/amd/amdgpu/amdgpu_mode.h | 1 + .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 2 ++ .../drm/amd/display/amdgpu_dm/amdgpu_dm_irq.c | 33 ++++++++++--------- 3 files changed, 21 insertions(+), 15 deletions(-) diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_mode.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_mode.h index 8069fc41cc7f..7c784277396a 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_mode.h +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_mode.h @@ -509,6 +509,7 @@ struct amdgpu_crtc { struct drm_pending_vblank_event *event; bool wb_pending; + bool wb_frame_done; bool wb_enabled; struct drm_writeback_connector *wb_conn; }; diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c index d67dcaa3fa8f..0f5453649200 100644 --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c @@ -4521,6 +4521,7 @@ bool amdgpu_dm_crtc_complete_writeback(struct amdgpu_crtc *acrtc) spin_lock_irqsave(&acrtc->wb_conn->job_lock, flags); pending = acrtc->wb_pending; acrtc->wb_pending = false; + acrtc->wb_frame_done = false; spin_unlock_irqrestore(&acrtc->wb_conn->job_lock, flags); if (!pending) @@ -4988,6 +4989,7 @@ static void dm_set_writeback(struct amdgpu_display_manager *dm, * cannot run its matching vblank_put before this get. */ WARN_ON(drm_crtc_vblank_get(&acrtc->base)); + acrtc->wb_frame_done = false; acrtc->wb_pending = true; } diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_irq.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_irq.c index c5467f34c51f..4de7fb264cb2 100644 --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_irq.c +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_irq.c @@ -1974,23 +1974,26 @@ static void dm_crtc_high_irq(void *interrupt_params) return; if (acrtc->wb_conn && acrtc->wb_pending) { - struct dc_stream_state *stream = acrtc->dm_irq_params.stream; - unsigned int v_total, refresh_hz; - - v_total = stream->adjust.v_total_max ? - stream->adjust.v_total_max : stream->timing.v_total; - refresh_hz = div_u64((uint64_t) stream->timing.pix_clk_100hz * - 100LL, (v_total * stream->timing.h_total)); - mdelay(1000 / refresh_hz); - - /* - * Completion (signalling the out fence and releasing the vblank - * reference taken in dm_set_writeback()) is handled by the shared - * helper, which is also used by the teardown path. - */ - if (amdgpu_dm_crtc_complete_writeback(acrtc)) + if (acrtc->wb_frame_done) { + /* + * Second vblank: the DMA for the captured frame has + * had a full frame period to flush to memory. Signal + * the out fence now. + */ + amdgpu_dm_crtc_complete_writeback(acrtc); + } else { + /* + * First vblank after arming: the frame has been + * scanned out and the DMA is finishing. Disable + * writeback immediately to prevent the hardware from + * starting a new capture that would overwrite the + * buffer. Signal completion on the next vblank to + * ensure the DMA is fully flushed to memory. + */ dc_stream_fc_disable_writeback(adev->dm.dc, acrtc->dm_irq_params.stream, 0); + acrtc->wb_frame_done = true; + } } vrr_active = amdgpu_dm_crtc_vrr_active_irq(acrtc); -- 2.43.0
