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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" color="#000000" style="font-size:11pt"><b>From:</b> Tuikov, Luben <Luben.Tuikov@amd.com><br>
<b>Sent:</b> Friday, April 8, 2022 9:33 AM<br>
<b>To:</b> Powell, Darren <Darren.Powell@amd.com>; amd-gfx@lists.freedesktop.org <amd-gfx@lists.freedesktop.org><br>
<b>Cc:</b> Quan, Evan <Evan.Quan@amd.com>; Wenhui.Sheng@amd.com <Wenhui.Sheng@amd.com>; Grodzovsky, Andrey <Andrey.Grodzovsky@amd.com><br>
<b>Subject:</b> Re: [PATCH 1/1] amdgpu/pm: Clarify Documentation of error handling in send_smc_mesg</font>
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<div class="PlainText">I'd add who and how is the message dropped, and also mention that we're unable<br>
to recognize a dropped message.<br>
<br>
On 2022-04-07 22:26, Darren Powell wrote:<br>
> Contrary to the smu_cmn_send_smc_msg_with_param documentation, two<br>
> cases exist where messages are silently dropped with no error returned<br>
> to the caller. These cases occur in unusual situations where either:<br>
> 1. the caller is a virtual GPU, or<br>
<br>
The caller? Isn't this code executed on a CPU sending to the SMU (which lives on a GPU)?<br>
[DP] Great point, will fix</div>
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> 2. a PCI recovery is underway and the HW is not yet in sync with the SW<br>
> <br>
> For more details see<br>
> commit 4ea5081c82c4 ("drm/amd/powerplay: enable SMC message filter")<br>
> commit bf36b52e781d ("drm/amdgpu: Avoid accessing HW when suspending SW state")<br>
> <br>
> Signed-off-by: Darren Powell <darren.powell@amd.com><br>
> ---<br>
> drivers/gpu/drm/amd/pm/swsmu/smu_cmn.c | 7 +++++--<br>
> 1 file changed, 5 insertions(+), 2 deletions(-)<br>
> <br>
> diff --git a/drivers/gpu/drm/amd/pm/swsmu/smu_cmn.c b/drivers/gpu/drm/amd/pm/swsmu/smu_cmn.c<br>
> index b8d0c70ff668..b1bd1990c88b 100644<br>
> --- a/drivers/gpu/drm/amd/pm/swsmu/smu_cmn.c<br>
> +++ b/drivers/gpu/drm/amd/pm/swsmu/smu_cmn.c<br>
> @@ -356,12 +356,15 @@ int smu_cmn_wait_for_response(struct smu_context *smu)<br>
> * completion of the command, and return back a value from the SMU in<br>
> * @read_arg pointer.<br>
> *<br>
> - * Return 0 on success, -errno on error, if we weren't able to send<br>
> + * Return 0 on success, or if the message is dropped.<br>
> + * On error, -errno is returned if we weren't able to send<br>
<br>
Something like this:<br>
<br>
Return 0 on success, -errno on error. If the message was dropped<br>
due to PCI bus recovery or sending to a virtual GPU, we're unable<br>
to detect this and success is also returned.<br>
<br>
> * the message or if the message completed with some kind of<br>
> * error. See __smu_cmn_reg2errno() for details of the -errno.<br>
> *<br>
> * If we weren't able to send the message to the SMU, we also print<br>
> - * the error to the standard log.<br>
> + * the error to the standard log. Dropped messages can be caused<br>
> + * due to PCI slot recovery or attempting to send from a virtual GPU,<br>
> + * and do not print an error.<br>
<br>
This is a moot point with the clarification I suggested above and I'd remove that.<br>
[DP] sounds more succinct, will address in v2</div>
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> *<br>
> * Command completion status is printed only if the -errno is<br>
> * -EREMOTEIO, indicating that the SMU returned back an<br>
> <br>
> base-commit: 4585c45a6a66cb17cc97f4370457503746e540b7<br>
<br>
Regards,<br>
-- <br>
Luben<br>
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