I'd add who and how is the message dropped, and also mention that we're unable
to recognize a dropped message.
On 2022-04-07 22:26, Darren Powell wrote:
> 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
The caller? Isn't this code executed on a CPU sending to the SMU (which lives on a GPU)?
> 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@xxxxxxx>
> ---
> 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
Something like this:
Return 0 on success, -errno on error. If the message was dropped
due to PCI bus recovery or sending to a virtual GPU, we're unable
to detect this and success is also returned.
> * 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.
This is a moot point with the clarification I suggested above and I'd remove that.
> *
> * Command completion status is printed only if the -errno is
> * -EREMOTEIO, indicating that the SMU returned back an
>
> base-commit: 4585c45a6a66cb17cc97f4370457503746e540b7
Regards,
--
Luben
