Re: [PATCH 2/8] mmc: sdhci-cadence: Use max-frequency property from device tree

[Tanmay Kathpalia <tanmay.kathpalia@altera.com>]

Thanks for your feedback, Peng.

On 11/18/2025 11:43 AM, Peng Fan wrote:
> On Mon, Nov 10, 2025 at 09:37:31AM -0800, Tanmay Kathpalia wrote:
>> When f_max parameter is 0 in sdhci_setup_cfg(), the function defaults
>> to using the maximum frequency from host controller capabilities register
>> instead of the max-frequency property parsed from device tree.
>>
>> The max-frequency property from device tree is parsed by mmc_of_parse()
>> and stored in plat->cfg.f_max, but sdhci_setup_cfg() was being called
>> with f_max=0, causing it to ignore the device tree value and use the
>> host capabilities register value instead.
>>
>> Fix this by passing plat->cfg.f_max to sdhci_setup_cfg() to ensure
>> the device tree specified maximum frequency is respected over the
>> hardware default.
>>
>> Signed-off-by: Tanmay Kathpalia <tanmay.kathpalia@altera.com>
>> Reviewed-by: Balsundar Ponnusamy <balsundar.ponnusamy@altera.com>
>> ---
>> drivers/mmc/sdhci-cadence.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/mmc/sdhci-cadence.c b/drivers/mmc/sdhci-cadence.c
>> index d9fda902076..f31437e5eeb 100644
>> --- a/drivers/mmc/sdhci-cadence.c
>> +++ b/drivers/mmc/sdhci-cadence.c
>> @@ -255,7 +255,7 @@ static int sdhci_cdns_probe(struct udevice *dev)
>>
>> 	host->mmc = &plat->mmc;
>> 	host->mmc->dev = dev;
>> -	ret = sdhci_setup_cfg(&plat->cfg, host, 0, 0);
>> +	ret = sdhci_setup_cfg(&plat->cfg, host, plat->cfg.f_max, 0);
> 
> plat is allocated by setting plat_auto in U_BOOT_DRIVER, but it is not
> zeroed. So f_max maybe a random value if max frequency is not set in
> device tree. You need clear it before mmc_of_parse or
> change to use dev_read_u32_default for parsing max frequency in mmc_of_parse.

I agree with your suggestion to use dev_read_u32_default in 
mmc_of_parse() for parsing the max-frequency property. This will ensure 
that plat->cfg.f_max is correctly set from the device tree, and if 
max-frequency is not specified, it will default to 0.
Since this change affects mmc-uclass.c in the MMC subsystem, I plan to 
submit a separate patch for that update to keep the changes organized.

> 
> Regards
> Peng
> 
>> 	if (ret)
>> 		return ret;
>>
>> -- 
>> 2.43.7
>>
>>