[PATCH 1/1] amdgpu/pm: Clarify documentation of error handling in send_smc_mesg

[Darren Powell]

Contrary to the smu_cmn_send_smc_msg_with_param documentation, two
cases exist where messages are silently dropped with no error returned
to the caller. These cases occur in unusual situations where either:
 1. the message target is a virtual GPU, or
 2. a PCI recovery is underway and the HW is not yet in sync with the SW

For more details see
 commit 4ea5081c82c4 ("drm/amd/powerplay: enable SMC message filter")
 commit bf36b52e781d ("drm/amdgpu: Avoid accessing HW when suspending SW state")

(v2)
  Reworked with suggestions from Luben & Paul

Signed-off-by: Darren Powell <darren.powell at amd.com>
---
 drivers/gpu/drm/amd/pm/swsmu/smu_cmn.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/pm/swsmu/smu_cmn.c b/drivers/gpu/drm/amd/pm/swsmu/smu_cmn.c
index b8d0c70ff668..8008ae5508e6 100644
--- a/drivers/gpu/drm/amd/pm/swsmu/smu_cmn.c
+++ b/drivers/gpu/drm/amd/pm/swsmu/smu_cmn.c
@@ -356,9 +356,11 @@ int smu_cmn_wait_for_response(struct smu_context *smu)
  * completion of the command, and return back a value from the SMU in
  * @read_arg pointer.
  *
- * Return 0 on success, -errno on error, if we weren't able to send
- * the message or if the message completed with some kind of
- * error. See __smu_cmn_reg2errno() for details of the -errno.
+ * Return 0 on success, -errno when a problem is encountered sending
+ * message or receiving reply. If there is a PCI bus recovery or
+ * the destination is a virtual GPU, the message is simply dropped and
+ * success is also returned.
+ * See __smu_cmn_reg2errno() for details of the -errno.
  *
  * If we weren't able to send the message to the SMU, we also print
  * the error to the standard log.

base-commit: 4585c45a6a66cb17cc97f4370457503746e540b7
-- 
2.35.1