From: Mukul Joshi <[email protected]>
Introduce a debugfs-controlled bitmap, amdgpu_ualink_drop_msg_bitmap,
where each bit corresponds to a value from
enum AMDGPU_UALINK_PROTOCOL_MESSAGES (e.g. NPA-REQ, NPA-RSP, NPA-FAIL,
NPA-REVOKE, NPA-RELEASE).
When a bit is set, the next incoming message of that type is dropped
in amdgpu_ualink_process_irq() and the bit is atomically cleared via
test_and_clear_bit(), so subsequent incoming messages are processed
normally. This allows exercising the UALink connection reset and
recovery paths (NPA-RSP timeout on the importer, retransmit/teardown
on the exporter, etc.) by injecting a single packet loss from
userspace, e.g.:
# drop one NPA-REQ
echo 0x08 > /sys/kernel/debug/dri/0/amdgpu_ualink_drop_msg_bitmap
# drop one NPA-RSP
echo 0x10 > /sys/kernel/debug/dri/0/amdgpu_ualink_drop_msg_bitmap
The bitmap lives in struct amdgpu_ualink_mgr and is exposed via
debugfs_create_ulong() next to the existing amdgpu_ualink_test entry.
Signed-off-by: Mukul Joshi <[email protected]>
Reviewed-by: Felix Kuehling <[email protected]>
Signed-off-by: Alex Deucher <[email protected]>
---
drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c | 14 ++++++++++++++
drivers/gpu/drm/amd/amdgpu/amdgpu_ualink.c | 13 +++++++++++++
drivers/gpu/drm/amd/amdgpu/amdgpu_ualink.h | 16 ++++++++++++++++
3 files changed, 43 insertions(+)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
index 132d054900b5b..d80fe17556dab 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
@@ -2229,6 +2229,20 @@ int amdgpu_debugfs_init(struct amdgpu_device *adev)
debugfs_create_file("amdgpu_benchmark", 0200, root, adev,
&amdgpu_benchmark_fops);
+ /* Debug-only: bitmap of incoming UALink protocol messages to drop.
+ * Each bit position corresponds to an enum
AMDGPU_UALINK_PROTOCOL_MESSAGES
+ * value. Setting a bit causes exactly one matching incoming packet to
be
+ * dropped, after which the bit auto-clears and traffic resumes. Used to
+ * exercise the connection reset paths.
+ *
+ * Examples (drop one NPA-REQ):
+ * echo 0x8 > /sys/kernel/debug/dri/0/amdgpu_ualink_drop_msg_bitmap
+ * (drop one NPA-RSP):
+ * echo 0x10 > /sys/kernel/debug/dri/0/amdgpu_ualink_drop_msg_bitmap
+ */
+ debugfs_create_ulong("amdgpu_ualink_drop_msg_bitmap", 0600, root,
+ &adev->ualink.drop_msg_bitmap);
+
adev->debugfs_vbios_blob.data = adev->bios;
adev->debugfs_vbios_blob.size = adev->bios_size;
debugfs_create_blob("amdgpu_vbios", 0444, root,
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ualink.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_ualink.c
index e21c48212f0a4..4e49ff0be6e35 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ualink.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ualink.c
@@ -5394,6 +5394,19 @@ static int amdgpu_ualink_process_irq(struct
amdgpu_device *adev,
dev_dbg(adev->dev, "Got MSG: remote acc_id %u msg_type %u\n",
src_acc_id, msg_type);
+ /* Debug hook: if the bit corresponding to this msg_type is set in
+ * drop_msg_bitmap, drop this single packet and clear the bit so that
+ * any subsequent incoming messages are processed normally. Used to
+ * exercise the connection reset/recovery paths via debugfs.
+ */
+ if (msg_type < BITS_PER_LONG &&
+ test_and_clear_bit(msg_type, &adev->ualink.drop_msg_bitmap)) {
+ dev_warn(adev->dev,
+ "DROP MSG (debugfs): src acc_id %u msg_type %u dw[0-3]
0x%x 0x%x 0x%x 0x%x\n",
+ src_acc_id, msg_type, dw0, dw1, dw2, dw3);
+ return handled;
+ }
+
switch (msg_type) {
case AMDGPU_UALINK_HELLO_MSG:
receiver_acc_id = (dw0 >>
AMDGPU_UALINK_HELLO_MSG_RECV_ACCID_SHIFT) &
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ualink.h
b/drivers/gpu/drm/amd/amdgpu/amdgpu_ualink.h
index fa116ef44cb50..d4d4ca0199dc7 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ualink.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ualink.h
@@ -342,6 +342,22 @@ struct amdgpu_ualink_mgr {
/* Sequence number to track the need for TLB flushes */
atomic64_t last_flushed_tlb_seq;
+
+ /* Debug-only: bitmap of incoming UALink protocol messages to drop.
+ *
+ * Each bit position corresponds to a value from
+ * enum AMDGPU_UALINK_PROTOCOL_MESSAGES:
+ * BIT(AMDGPU_UALINK_NPA_REQ_MSG) drops one incoming NPA-REQ.
+ * BIT(AMDGPU_UALINK_NPA_RSP_MSG) drops one incoming NPA-RSP.
+ *
+ * On reception of a message whose corresponding bit is set, the bit
+ * is atomically cleared and the message is silently dropped. This
+ * means at most one packet per set bit is dropped; any further
+ * incoming packets of the same type are processed normally. This is
+ * intended to exercise the connection reset / recovery paths from a
+ * debugfs handle.
+ */
+ unsigned long drop_msg_bitmap;
};
int amdgpu_ualink_init_interrupt(struct amdgpu_device *adev);
--
2.55.0
