[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 caller 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")

Signed-off-by: Darren Powell <darren.powell at amd.com>
---
 drivers/gpu/drm/amd/pm/swsmu/smu_cmn.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 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..b1bd1990c88b 100644
--- a/drivers/gpu/drm/amd/pm/swsmu/smu_cmn.c
+++ b/drivers/gpu/drm/amd/pm/swsmu/smu_cmn.c
@@ -356,12 +356,15 @@ 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
+ * Return 0 on success, or if the message is dropped.
+ * On error, -errno is returned 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.
  *
  * If we weren't able to send the message to the SMU, we also print
- * the error to the standard log.
+ * the error to the standard log. Dropped messages can be caused
+ * due to PCI slot recovery or attempting to send from a virtual GPU,
+ * and do not print an error.
  *
  * Command completion status is printed only if the -errno is
  * -EREMOTEIO, indicating that the SMU returned back an

base-commit: 4585c45a6a66cb17cc97f4370457503746e540b7
-- 
2.35.1