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

[Powell, Darren]

[AMD Official Use Only]

I needed to dig further down to find the message map, I had been looking back in mailing list looking for clarification but hadn't found anything.
Will reword
Thanks
Darren
________________________________
From: Lazar, Lijo <Lijo.Lazar at amd.com>
Sent: Tuesday, April 12, 2022 12:19 AM
To: Powell, Darren <Darren.Powell at amd.com>; amd-gfx at lists.freedesktop.org <amd-gfx at lists.freedesktop.org>
Cc: Tuikov, Luben <Luben.Tuikov at amd.com>; Quan, Evan <Evan.Quan at amd.com>; Grodzovsky, Andrey <Andrey.Grodzovsky at amd.com>; pmenzel at molgen.mpg.de <pmenzel at molgen.mpg.de>
Subject: Re: [PATCH 1/1] amdgpu/pm: Clarify documentation of error handling in send_smc_mesg



On 4/12/2022 9:38 AM, 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 message target is a virtual GPU, or

This is not fully correct - only messages which are not valid for
virtual GPU are dropped, not all.

Thanks,
Lijo

>   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
>
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