Re: [PATCH v1] Revert "mmc: mmc-uclass: Use max-frequency from device tree with default handling"

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

Hi Marek,


On 1/9/2026 4:51 AM, Marek Vasut wrote:
> On 1/8/26 12:40 PM, Tanmay Kathpalia wrote:
>> This reverts commit aebb523a23818a8ee4199c9532b51e3d4020696f.
>>
>> The change to use dev_read_u32_default() with a default value of 0
>> causes regression for host controller drivers that hardcode f_max
>> before calling mmc_of_parse().
>>
>> When the "max-frequency" property is not specified in the device tree,
>> dev_read_u32_default() returns 0, which overwrites the previously
>> configured f_max value set by the driver. This effectively resets
>> the maximum frequency to 0, breaking MMC functionality for those
>> controllers.
>>
>> Revert to the original dev_read_u32() behavior which only updates
>> cfg->f_max when the "max-frequency" property is explicitly present
>> in the device tree, preserving driver-configured values otherwise.
>>
>> Signed-off-by: Tanmay Kathpalia <tanmay.kathpalia@altera.com>
>> ---
>>   drivers/mmc/mmc-uclass.c | 9 ++-------
>>   1 file changed, 2 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/mmc/mmc-uclass.c b/drivers/mmc/mmc-uclass.c
>> index bf0bea93853..2f4dc5bd887 100644
>> --- a/drivers/mmc/mmc-uclass.c
>> +++ b/drivers/mmc/mmc-uclass.c
>> @@ -243,13 +243,8 @@ int mmc_of_parse(struct udevice *dev, struct 
>> mmc_config *cfg)
>>           return -EINVAL;
>>       }
>> -    /*
>> -     * Maximum frequency is obtained from the optional "max- 
>> frequency" property.
>> -     * If not specified in device tree, defaults to 0 and 
>> sdhci_setup_cfg()
>> -     * will set the MMC configuration maximum frequency to the host 
>> controller's
>> -     * maximum base clock frequency from capabilities register.
>> -     */
>> -    cfg->f_max = dev_read_u32_default(dev, "max-frequency", 0);
>> +    /* f_max is obtained from the optional "max-frequency" property */
>> +    dev_read_u32(dev, "max-frequency", &cfg->f_max);
> 
> Why not do this then ?
> 
> cfg->f_max = dev_read_u32_default(dev, "max-frequency", cfg->f_max);

Good point — you're right.
cfg->f_max = dev_read_u32_default(dev, "max-frequency", cfg->f_max);
is cleaner and safer.

I'll send a follow-up patch with this change.

Thanks!