linux-kernel - [PATCH 5/5] drm/msm/dpu: rate limit snapshot capture for mmu faults

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Message-ID: <20240628214848.4075651-6-quic_abhinavk@quicinc.com>
Date: Fri, 28 Jun 2024 14:48:47 -0700
From: Abhinav Kumar <quic_abhinavk@...cinc.com>
To: <freedreno@...ts.freedesktop.org>, Rob Clark <robdclark@...il.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Dmitry Baryshkov
	<dmitry.baryshkov@...aro.org>,
        Sean Paul <sean@...rly.run>,
        Marijn Suijten
	<marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, "Daniel
 Vetter" <daniel@...ll.ch>
CC: <dri-devel@...ts.freedesktop.org>, <quic_jesszhan@...cinc.com>,
        <swboyd@...omium.org>, <dianders@...omium.org>,
        <linux-arm-msm@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH 5/5] drm/msm/dpu: rate limit snapshot capture for mmu faults

There is no recovery mechanism in place yet to recover from mmu
faults for DPU. We can only prevent the faults by making sure there
is no misconfiguration.

Rate-limit the snapshot capture for mmu faults to once per
msm_kms_init_aspace() as that should be sufficient to capture
the snapshot for debugging otherwise there will be a lot of
dpu snapshots getting captured for the same fault which is
redundant and also might affect capturing even one snapshot
accurately.

Signed-off-by: Abhinav Kumar <quic_abhinavk@...cinc.com>
---
 drivers/gpu/drm/msm/msm_kms.c | 6 +++++-
 drivers/gpu/drm/msm/msm_kms.h | 3 +++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/msm_kms.c b/drivers/gpu/drm/msm/msm_kms.c
index d5d3117259cf..90a333920c01 100644
--- a/drivers/gpu/drm/msm/msm_kms.c
+++ b/drivers/gpu/drm/msm/msm_kms.c
@@ -168,7 +168,10 @@ static int msm_kms_fault_handler(void *arg, unsigned long iova, int flags, void
 {
 	struct msm_kms *kms = arg;
 
-	msm_disp_snapshot_state(kms->dev);
+	if (!kms->fault_snapshot_capture) {
+		msm_disp_snapshot_state(kms->dev);
+		kms->fault_snapshot_capture++;
+	}
 
 	return -ENOSYS;
 }
@@ -208,6 +211,7 @@ struct msm_gem_address_space *msm_kms_init_aspace(struct drm_device *dev)
 		mmu->funcs->destroy(mmu);
 	}
 
+	kms->fault_snapshot_capture = 0;
 	msm_mmu_set_fault_handler(aspace->mmu, kms, msm_kms_fault_handler);
 
 	return aspace;
diff --git a/drivers/gpu/drm/msm/msm_kms.h b/drivers/gpu/drm/msm/msm_kms.h
index 1e0c54de3716..240b39e60828 100644
--- a/drivers/gpu/drm/msm/msm_kms.h
+++ b/drivers/gpu/drm/msm/msm_kms.h
@@ -134,6 +134,9 @@ struct msm_kms {
 	int irq;
 	bool irq_requested;
 
+	/* rate limit the snapshot capture to once per attach */
+	int fault_snapshot_capture;
+
 	/* mapper-id used to request GEM buffer mapped for scanout: */
 	struct msm_gem_address_space *aspace;
 
-- 
2.44.0