Re: [PATCH 2/2] mmc: dw_mmc: prevent to set the wrong value

[Jaehoon Chung <jh80.chung@samsung.com>]

Hi Shawn,

On 05/04/2016 07:35 PM, Shawn Lin wrote:
> 在 2016/5/4 15:14, Jaehoon Chung 写道:
>> If there is no vqmmc, real voltage should not change.
>> Then it needs to maintain the previous status for UHS_REG register.
>> It means that it doesn't need to set any bit.
>>
>> Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
>> ---
>>  drivers/mmc/host/dw_mmc.c | 12 ++++++++++++
>>  1 file changed, 12 insertions(+)
>>
>> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
>> index 28602cc..6bd8018 100644
>> --- a/drivers/mmc/host/dw_mmc.c
>> +++ b/drivers/mmc/host/dw_mmc.c
>> @@ -1418,7 +1418,19 @@ static int dw_mci_switch_voltage(struct mmc_host *mmc, struct mmc_ios *ios)
>>                       ret, uhs & v18 ? "1.8" : "3.3");
>>              return -EAGAIN;
>>          }
>> +    } else {
>> +        /*
>> +         * If there isn't vqmmc, it should fail to switch voltage.
>> +         * Then it needs to maintain the previous status.
>> +         * If ios->signal_voltage is 3.3v, it means that previous
>> +         * voltages was 1.8v.
>> +         */
>> +        if (ios->signal_voltage == MMC_SIGNAL_VOLTAGE_330)
>> +            uhs |= v18;
>> +        else
>> +            uhs &= ~v18;
> 
> I think we can just set uhs after seting vqmmc correctly. So
> how about changing like this?

Yes, it's more readable than mine. Thanks.

Best Regards,
Jaehoon Chung

> 
>         uhs = mci_readl(host, UHS_REG);
> 
>         if (!IS_ERR(mmc->supply.vqmmc)) {
>                 ret = mmc_regulator_set_vqmmc(mmc, ios);
>                 if (ret) {
>                         dev_dbg(&mmc->class_dev,
>                                 "Regulator set error %d - %s V\n",
>                                  ret, uhs & v18 ? "3.3" : "1.8");
>                         return -EAGAIN;
>                 }
>                 if (ios->signal_voltage == MMC_SIGNAL_VOLTAGE_330)
>                         uhs &= ~v18;
>                 else
>                         uhs |= v18;
>         }
>         mci_writel(host, UHS_REG, uhs);
> 
> 
>>      }
>> +
>>      mci_writel(host, UHS_REG, uhs);
>>
>>      return 0;
>>
> 
>