[U-Boot] [PATCH 12/22] mmc: Enable signal voltage to be selected from mmc core

[Simon Glass]

Hi Jean-Jacques,

On 15 May 2017 at 08:18, Jean-Jacques Hiblot <jjhiblot at ti.com> wrote:
>
>
> On 15/05/2017 05:28, Simon Glass wrote:
>>
>> Hi Jen-Jacques,
>>
>> On 12 May 2017 at 12:16, Jean-Jacques Hiblot <jjhiblot at ti.com> wrote:
>>>
>>> From: Kishon Vijay Abraham I <kishon at ti.com>
>>>
>>> Add a new function *mmc_set_signal_voltage* in mmc core
>>> which can be used during mmc initialization to select the
>>> signal voltage. Platform driver should use the set_ios
>>> callback function to select the signal voltage.
>>>
>>> Signed-off-by: Kishon Vijay Abraham I <kishon at ti.com>
>>> Signed-off-by: Jean-Jacques Hiblot <jjhiblot at ti.com>
>>> ---
>>>   drivers/mmc/mmc.c | 15 +++++++++++++++
>>>   include/mmc.h     |  5 +++++
>>>   2 files changed, 20 insertions(+)
>>>
>>> diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c
>>> index 2ae6f1c..10af81d 100644
>>> --- a/drivers/mmc/mmc.c
>>> +++ b/drivers/mmc/mmc.c
>>> @@ -29,6 +29,7 @@ static const unsigned int sd_au_size[] = {
>>>          SZ_4M / 512,    SZ_8M / 512,            (SZ_8M + SZ_4M) / 512,
>>>          SZ_16M / 512,   (SZ_16M + SZ_8M) / 512, SZ_32M / 512,   SZ_64M /
>>> 512,
>>>   };
>>> +static int mmc_set_signal_voltage(struct mmc *mmc, uint signal_voltage);
>>>
>>>   #if CONFIG_IS_ENABLED(MMC_TINY)
>>>   static struct mmc mmc_static;
>>> @@ -1247,6 +1248,12 @@ struct mode_width_tuning {
>>>          uint widths;
>>>   };
>>>
>>> +static int mmc_set_signal_voltage(struct mmc *mmc, uint signal_voltage)
>>> +{
>>> +       mmc->signal_voltage = signal_voltage;
>>> +       return mmc_set_ios(mmc);
>>> +}
>>> +
>>>   static const struct mode_width_tuning sd_modes_by_pref[] = {
>>>          {
>>>                  .mode = SD_HS,
>>> @@ -1935,6 +1942,14 @@ int mmc_start_init(struct mmc *mmc)
>>>                  return err;
>>>   #endif
>>>          mmc->ddr_mode = 0;
>>> +
>>> +       /* First try to set 3.3V. If it fails set to 1.8V */
>>> +       err = mmc_set_signal_voltage(mmc, MMC_SIGNAL_VOLTAGE_330);
>>> +       if (err != 0)
>>> +               err = mmc_set_signal_voltage(mmc,
>>> MMC_SIGNAL_VOLTAGE_180);
>>> +       if (err != 0)
>>> +               printf("failed to set signal voltage\n");
>>
>> Return error?
>
> Maybe we should. I don't know.
> Setting signal voltage is optional (at least for most modes), some platforms
> don't support it. So I wouldn't exit on this kind of error. Those 2 calls to
> mmc_set_signal_voltage() are here merely to turn on regulators before doing
> the card init. If setting voltage is required and fails, the init process
> won't go very far.

If there is no regulator, then how about checking the error return
value, and if it is -ENODEV, continue. But any other error, you exit.

>
>>> +
>>>          mmc_set_bus_width(mmc, 1);
>>>          mmc_set_clock(mmc, 1);
>>>
>>> diff --git a/include/mmc.h b/include/mmc.h
>>> index 9f20eb4..89cb26c 100644
>>> --- a/include/mmc.h
>>> +++ b/include/mmc.h
>>> @@ -266,6 +266,10 @@
>>>   #define ENHNCD_SUPPORT         (0x2)
>>>   #define PART_ENH_ATTRIB                (0x1f)
>>>
>>> +#define MMC_SIGNAL_VOLTAGE_330 1
>>> +#define MMC_SIGNAL_VOLTAGE_180 2
>>> +#define MMC_SIGNAL_VOLTAGE_120 3
>>> +
>>>   /* Maximum block size for MMC */
>>>   #define MMC_MAX_BLOCK_LEN      512
>>>
>>> @@ -452,6 +456,7 @@ struct mmc {
>>>          int high_capacity;
>>>          uint bus_width;
>>>          uint clock;
>>> +       uint signal_voltage;
>>
>> Comment. What does this value mean? What units is it? Millivolts or
>> something else?
>
> it's more an enum than a value with a physical meaning (like mV). I'll
> change this in the next version to be a real enum.
>
>>
>>>          uint card_caps;
>>>          uint ocr;
>>>          uint dsr;
>>> --
>>> 1.9.1
>>

Regards,
Simon