[PATCH] drm/msm: Wait for MMU devcoredump when waiting for GMU

[Connor Abbott]

If there is a flood of faults then the MMU can become saturated while it
waits for the kernel to process the first fault and resume it, so that
the GMU becomes blocked. This is mainly a problem when the kernel reads
the state of the GPU for a devcoredump, because this takes a while. If
we timeout waiting for the GMU, check if this has happened and retry
after we're finished.

Signed-off-by: Connor Abbott <cwabbott0 at gmail.com>
---
 drivers/gpu/drm/msm/adreno/a6xx_gmu.c   | 21 ++++++++++++++++++---
 drivers/gpu/drm/msm/adreno/a6xx_hfi.c   | 21 ++++++++++++++++++---
 drivers/gpu/drm/msm/adreno/adreno_gpu.c | 11 +++++++++++
 drivers/gpu/drm/msm/adreno/adreno_gpu.h |  2 ++
 4 files changed, 49 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
index 28e6705c6da682c7b41c748e375dda59a6551898..6ec396fab22d194481a76d30b2d36ea5fb662241 100644
--- a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
+++ b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
@@ -340,6 +340,7 @@ int a6xx_gmu_set_oob(struct a6xx_gmu *gmu, enum a6xx_gmu_oob_state state)
 	int ret;
 	u32 val;
 	int request, ack;
+	struct a6xx_gpu *a6xx_gpu = container_of(gmu, struct a6xx_gpu, gmu);
 
 	WARN_ON_ONCE(!mutex_is_locked(&gmu->lock));
 
@@ -363,9 +364,23 @@ int a6xx_gmu_set_oob(struct a6xx_gmu *gmu, enum a6xx_gmu_oob_state state)
 	/* Trigger the equested OOB operation */
 	gmu_write(gmu, REG_A6XX_GMU_HOST2GMU_INTR_SET, 1 << request);
 
-	/* Wait for the acknowledge interrupt */
-	ret = gmu_poll_timeout(gmu, REG_A6XX_GMU_GMU2HOST_INTR_INFO, val,
-		val & (1 << ack), 100, 10000);
+	do {
+		/* Wait for the acknowledge interrupt */
+		ret = gmu_poll_timeout(gmu, REG_A6XX_GMU_GMU2HOST_INTR_INFO, val,
+			val & (1 << ack), 100, 10000);
+
+		if (!ret)
+			break;
+
+		if (completion_done(&a6xx_gpu->base.fault_coredump_done))
+			break;
+
+		/* We may timeout because the GMU is temporarily wedged from
+		 * pending faults from the GPU and we are taking a devcoredump.
+		 * Wait until the MMU is resumed and try again.
+		 */
+		wait_for_completion(&a6xx_gpu->base.fault_coredump_done);
+	} while (true);
 
 	if (ret)
 		DRM_DEV_ERROR(gmu->dev,
diff --git a/drivers/gpu/drm/msm/adreno/a6xx_hfi.c b/drivers/gpu/drm/msm/adreno/a6xx_hfi.c
index 8e69b1e8465711837151725c8f70e7b4b16a368e..4e775ca757ce3649ac238d25cebfd7eb693fda61 100644
--- a/drivers/gpu/drm/msm/adreno/a6xx_hfi.c
+++ b/drivers/gpu/drm/msm/adreno/a6xx_hfi.c
@@ -104,10 +104,25 @@ static int a6xx_hfi_wait_for_msg_interrupt(struct a6xx_gmu *gmu, u32 id, u32 seq
 {
 	int ret;
 	u32 val;
+	struct a6xx_gpu *a6xx_gpu = container_of(gmu, struct a6xx_gpu, gmu);
+
+	do {
+		/* Wait for a response */
+		ret = gmu_poll_timeout(gmu, REG_A6XX_GMU_GMU2HOST_INTR_INFO, val,
+			val & A6XX_GMU_GMU2HOST_INTR_INFO_MSGQ, 100, 1000000);
+
+		if (!ret)
+			break;
 
-	/* Wait for a response */
-	ret = gmu_poll_timeout(gmu, REG_A6XX_GMU_GMU2HOST_INTR_INFO, val,
-		val & A6XX_GMU_GMU2HOST_INTR_INFO_MSGQ, 100, 1000000);
+		if (completion_done(&a6xx_gpu->base.fault_coredump_done))
+			break;
+
+		/* We may timeout because the GMU is temporarily wedged from
+		 * pending faults from the GPU and we are taking a devcoredump.
+		 * Wait until the MMU is resumed and try again.
+		 */
+		wait_for_completion(&a6xx_gpu->base.fault_coredump_done);
+	} while (true);
 
 	if (ret) {
 		DRM_DEV_ERROR(gmu->dev,
diff --git a/drivers/gpu/drm/msm/adreno/adreno_gpu.c b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
index f1230465bf0d0840274a6eb03a10c4df3a7a68d3..19181b6fddfd518e2f60324da1a7087458115e40 100644
--- a/drivers/gpu/drm/msm/adreno/adreno_gpu.c
+++ b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
@@ -293,6 +293,7 @@ int adreno_fault_handler(struct msm_gpu *gpu, unsigned long iova, int flags,
 			 struct adreno_smmu_fault_info *info, const char *block,
 			 u32 scratch[4])
 {
+	struct adreno_gpu *adreno_gpu = container_of(gpu, struct adreno_gpu, base);
 	struct msm_drm_private *priv = gpu->dev->dev_private;
 	struct msm_mmu *mmu = to_msm_vm(gpu->vm)->mmu;
 	const char *type = "UNKNOWN";
@@ -345,6 +346,11 @@ int adreno_fault_handler(struct msm_gpu *gpu, unsigned long iova, int flags,
 		/* Turn off the hangcheck timer to keep it from bothering us */
 		timer_delete(&gpu->hangcheck_timer);
 
+		/* Let any concurrent GMU transactions know that the MMU may be
+		 * blocked for a while and they should wait on us.
+		 */
+		reinit_completion(&adreno_gpu->fault_coredump_done);
+
 		fault_info.ttbr0 = info->ttbr0;
 		fault_info.iova  = iova;
 		fault_info.flags = flags;
@@ -352,6 +358,8 @@ int adreno_fault_handler(struct msm_gpu *gpu, unsigned long iova, int flags,
 		fault_info.block = block;
 
 		msm_gpu_fault_crashstate_capture(gpu, &fault_info);
+
+		complete_all(&adreno_gpu->fault_coredump_done);
 	}
 
 	return 0;
@@ -1238,6 +1246,9 @@ int adreno_gpu_init(struct drm_device *drm, struct platform_device *pdev,
 	if (ret)
 		return ret;
 
+	init_completion(&adreno_gpu->fault_coredump_done);
+	complete_all(&adreno_gpu->fault_coredump_done);
+
 	pm_runtime_set_autosuspend_delay(dev,
 		adreno_gpu->info->inactive_period);
 	pm_runtime_use_autosuspend(dev);
diff --git a/drivers/gpu/drm/msm/adreno/adreno_gpu.h b/drivers/gpu/drm/msm/adreno/adreno_gpu.h
index 9dc93c247196d5b8b3659157f7aeea81809d4056..f16556c6f2921708e740ecd47f5b4668e87700aa 100644
--- a/drivers/gpu/drm/msm/adreno/adreno_gpu.h
+++ b/drivers/gpu/drm/msm/adreno/adreno_gpu.h
@@ -179,6 +179,8 @@ struct adreno_gpu {
 	uint16_t speedbin;
 	const struct adreno_gpu_funcs *funcs;
 
+	struct completion fault_coredump_done;
+
 	/* interesting register offsets to dump: */
 	const unsigned int *registers;
 

---
base-commit: 8290d37ad2b087bbcfe65fa5bcaf260e184b250a
change-id: 20250718-msm-gmu-fault-wait-465543a718fa

Best regards,
-- 
Connor Abbott <cwabbott0 at gmail.com>