Re: [PATCH 1/2] platform/x86/amd/pmc: Fix fetching DRAM size mechanism

[Mario Limonciello <mario.limonciello@amd.com>]

On 10/9/2023 09:47, Shyam Sundar S K wrote:
> amd_pmc_get_dram_size() is used to get the DRAM size information. But in
> the current code, mailbox command to get the DRAM size info is sent based
> on the values of dev->major and dev->minor.
> 
> But dev->major and dev->minor will have either junk or zero assigned to
> them until at least once a call to amd_pmc_get_smu_version() is made which
> ideally populates dev->major and dev->minor.
> 
> Add a missing amd_pmc_get_smu_version() call to amd_pmc_get_dram_size().
> 
> Fixes: be8325fb3d8c ("platform/x86/amd: pmc: Get STB DRAM size from PMFW")
> Suggested-by: Sanket Goswami <Sanket.Goswami@amd.com>
> Signed-off-by: Shyam Sundar S K <Shyam-sundar.S-k@amd.com>
> ---
> based on review-ilpo, can be added on top of recent stb changes

Hmm, so this is actually going to mean that we end up with a round trip 
call to the SMU as part of probe to get the version when STB is initialized.

I think that's going to translate to a longer amd_pmc startup time, 
which could be problematic if a platform leaves STB enabled by default.

At a minimum I would suggest to only do the version check when it's one 
that needs it (IE AMD_CPU_ID_YC right now).  But otherwise this s2d 
initialization can't happen the first time it's used?

> 
>   drivers/platform/x86/amd/pmc/pmc.c | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/platform/x86/amd/pmc/pmc.c b/drivers/platform/x86/amd/pmc/pmc.c
> index 1424c03c1f03..92adf4523736 100644
> --- a/drivers/platform/x86/amd/pmc/pmc.c
> +++ b/drivers/platform/x86/amd/pmc/pmc.c
> @@ -981,6 +981,10 @@ static int amd_pmc_get_dram_size(struct amd_pmc_dev *dev)
>   {
>   	int ret;
>   
> +	ret = amd_pmc_get_smu_version(dev);
> +	if (ret)
> +		return ret;
> +
>   	switch (dev->cpu_id) {
>   	case AMD_CPU_ID_YC:
>   		if (!(dev->major > 90 || (dev->major == 90 && dev->minor > 39))) {