[PATCH 2/2] drm/amdgpu: Rework retry fault removal

[Mukul Joshi]

Rework retry fault removal from the software filter by
storing an expired timestamp for a fault that is being removed.
When a new fault comes, and it matches an entry in the sw filter,
it will be added as a new fault only when its timestamp is greater
than the timestamp expiry of the fault in the sw filter.
This helps in avoiding stale faults being added back into the
filter and preventing legitimate faults from being handled.

Suggested-by: Felix Kuehling <Felix.Kuehling at amd.com>
Signed-off-by: Mukul Joshi <mukul.joshi at amd.com>
Reviewed-by: Philip Yang <Philip.Yang at amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c | 36 ++++++++++++++++++++++---
 drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.h |  1 +
 2 files changed, 34 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c
index 02a4c93673ce..fb811bc7214c 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c
@@ -387,8 +387,21 @@ bool amdgpu_gmc_filter_faults(struct amdgpu_device *adev,
 	while (fault->timestamp >= stamp) {
 		uint64_t tmp;
 
-		if (atomic64_read(&fault->key) == key)
-			return true;
+		if (atomic64_read(&fault->key) == key) {
+			/*
+			 * if we get a fault which is already present in
+			 * the fault_ring and the timestamp of
+			 * the fault is after the expired timestamp,
+			 * then this is a new fault that needs to be added
+			 * into the fault ring.
+			 */
+			if (fault->timestamp_expiry != 0 &&
+			    amdgpu_ih_ts_after(fault->timestamp_expiry,
+					       timestamp))
+				break;
+			else
+				return true;
+		}
 
 		tmp = fault->timestamp;
 		fault = &gmc->fault_ring[fault->next];
@@ -424,15 +437,32 @@ void amdgpu_gmc_filter_faults_remove(struct amdgpu_device *adev, uint64_t addr,
 {
 	struct amdgpu_gmc *gmc = &adev->gmc;
 	uint64_t key = amdgpu_gmc_fault_key(addr, pasid);
+	struct amdgpu_ih_ring *ih;
 	struct amdgpu_gmc_fault *fault;
+	uint32_t last_wptr;
+	uint64_t last_ts;
 	uint32_t hash;
 	uint64_t tmp;
 
+	ih = adev->irq.retry_cam_enabled ? &adev->irq.ih_soft : &adev->irq.ih1;
+	/* Get the WPTR of the last entry in IH ring */
+	last_wptr = amdgpu_ih_get_wptr(adev, ih);
+	/* Order wptr with ring data. */
+	rmb();
+	/* Get the timetamp of the last entry in IH ring */
+	last_ts = amdgpu_ih_decode_iv_ts(adev, ih, last_wptr, -1);
+
 	hash = hash_64(key, AMDGPU_GMC_FAULT_HASH_ORDER);
 	fault = &gmc->fault_ring[gmc->fault_hash[hash].idx];
 	do {
-		if (atomic64_cmpxchg(&fault->key, key, 0) == key)
+		if (atomic64_read(&fault->key) == key) {
+			/*
+			 * Update the timestamp when this fault
+			 * expired.
+			 */
+			fault->timestamp_expiry = last_ts;
 			break;
+		}
 
 		tmp = fault->timestamp;
 		fault = &gmc->fault_ring[fault->next];
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.h
index 0305b660cd17..9441e530f1dc 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.h
@@ -70,6 +70,7 @@ struct amdgpu_gmc_fault {
 	uint64_t	timestamp:48;
 	uint64_t	next:AMDGPU_GMC_FAULT_RING_ORDER;
 	atomic64_t	key;
+	uint64_t	timestamp_expiry:48;
 };
 
 /*
-- 
2.35.1