drm/msm: Hangcheck progress detection

If the hangcheck timer expires, check if the fw's position in the
cmdstream has advanced (changed) since last timer expiration, and
allow it up to three additional "extensions" to it's alotted time.
The intention is to continue to catch "shader stuck in a loop" type
hangs quickly, but allow more time for things that are actually
making forward progress.

Because we need to sample the CP state twice to detect if there has
not been progress, this also cuts the the timer's duration in half.

v2: Fix typo (REG_A6XX_CP_CSQ_IB2_STAT), add comment
v3: Only halve hangcheck timer duration for generations which
    support progress detection (hdanton); removed unused a5xx
    progress (without knowing how to adjust for data buffered
    in ROQ it is too likely to report a false negative)
v4: Comment updates to better describe the total hangcheck
    duration when progress detection is applied

Reviewed-by: Chia-I Wu <olvaffe@gmail.com>
Tested-by: Chia-I Wu <olvaffe@gmail.com> # dEQP-GLES2.functional.flush_finish.wait
Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Akhil P Oommen <quic_akhilpo@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/511584/
Link: https://lore.kernel.org/r/20221114193049.1533391-3-robdclark@gmail.com

1 files changed, 7 insertions, 1 deletions

diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h
index b2ea262296a4..d4e0ef608950 100644
--- a/drivers/gpu/drm/msm/msm_drv.h
+++ b/drivers/gpu/drm/msm/msm_drv.h
@@ -224,7 +224,13 @@ struct msm_drm_private {
 
 	struct drm_atomic_state *pm_state;
 
-	/* For hang detection, in ms */
+	/**
+	 * hangcheck_period: For hang detection, in ms
+	 *
+	 * Note that in practice, a submit/job will get at least two hangcheck
+	 * periods, due to checking for progress being implemented as simply
+	 * "have the CP position registers changed since last time?"
+	 */
 	unsigned int hangcheck_period;
 
 	/**