[PATCH 5.10 086/717] drm/msm/a6xx: Clear shadow on suspend

Greg Kroah-Hartman
2020-12-28T15:18:57Z

From: Rob Clark <robdclark@chromium.org>

[ Upstream commit e8b0b994c3a5881f0648d53f90435120089c56ad ]

Clear the shadow rptr on suspend. Otherwise, when we resume, we can
have a stale value until CP_WHERE_AM_I executes. If we suspend near
the ringbuffer wraparound point, this can lead to a chicken/egg
situation where we are waiting for ringbuffer space to write the
CP_WHERE_AM_I (or CP_INIT) packet, because we mistakenly believe that
the ringbuffer is full (due to stale rptr value in the shadow).

Fixes errors like:

[drm:adreno_wait_ring [msm]] *ERROR* timeout waiting for space in ringbuffer 0

in the resume path.

Fixes: d3a569fccfa0 ("drm/msm: a6xx: Use WHERE_AM_I for eligible targets")
Signed-off-by: Rob Clark <robdclark@chromium.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/msm/adreno/a6xx_gpu.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
index 948f3656c20ca..420ca4a0eb5f7 100644
--- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
+++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
@@ -1045,12 +1045,21 @@ static int a6xx_pm_suspend(struct msm_gpu *gpu)
{
struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
struct a6xx_gpu *a6xx_gpu = to_a6xx_gpu(adreno_gpu);
+ int i, ret;

trace_msm_gpu_suspend(0);

devfreq_suspend_device(gpu->devfreq.devfreq);

- return a6xx_gmu_stop(a6xx_gpu);
+ ret = a6xx_gmu_stop(a6xx_gpu);
+ if (ret)
+ return ret;
+
+ if (adreno_gpu->base.hw_apriv || a6xx_gpu->has_whereami)
+ for (i = 0; i < gpu->nr_rings; i++)
+ a6xx_gpu->shadow[i] = 0;
+
+ return 0;
}

static int a6xx_get_timestamp(struct msm_gpu *gpu, uint64_t *value)
--
2.27.0