[U-Boot] [PATCH v2 13/26] mmc: Enable signal voltage to be selected from mmc core

[Jean-Jacques Hiblot]

On 22/09/2017 15:54, Jaehoon Chung wrote:
> On 09/21/2017 11:30 PM, Jean-Jacques Hiblot 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 | 16 ++++++++++++++++
>>   include/mmc.h     |  8 ++++++++
>>   2 files changed, 24 insertions(+)
>>
>> diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c
>> index 536cd7f..46ec5e1 100644
>> --- a/drivers/mmc/mmc.c
>> +++ b/drivers/mmc/mmc.c
>> @@ -30,6 +30,8 @@ static const unsigned int sd_au_size[] = {
>>   	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;
>>   struct mmc *find_mmc_device(int dev_num)
>> @@ -1257,6 +1259,12 @@ 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,
>> @@ -1964,6 +1972,14 @@ 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");
>> +
> Well, it's confused. if 3.3v and 1.8v are failed, there is no problem?
> last signal value should be set to 1.8v. Is it correct?
If both 3.3v and 1.8v fail, then it may be because the underlying layer 
doesn't handle this properly (maybe it's using a fixed voltage, and 
refuses any switch).
If there is a real issue when turning on the signal voltage, it'll be 
handled later in the initialization process because the dialog with the 
sd/mmc will not work.

>
> Why didn't try to set the 1.2 voltage?
I didn't think of it. Is this allowed by the MMC spec ?

Jean-Jacques
>
>>   	mmc_set_bus_width(mmc, 1);
>>   	mmc_set_clock(mmc, 1);
>>   
>> diff --git a/include/mmc.h b/include/mmc.h
>> index 3e57887..e524963 100644
>> --- a/include/mmc.h
>> +++ b/include/mmc.h
>> @@ -272,6 +272,13 @@
>>   #define ENHNCD_SUPPORT		(0x2)
>>   #define PART_ENH_ATTRIB		(0x1f)
>>   
>> +enum mmc_voltage {
>> +	MMC_SIGNAL_VOLTAGE_000 = 0,
>> +	MMC_SIGNAL_VOLTAGE_120,
>> +	MMC_SIGNAL_VOLTAGE_180,
>> +	MMC_SIGNAL_VOLTAGE_330
>> +};
>> +
>>   /* Maximum block size for MMC */
>>   #define MMC_MAX_BLOCK_LEN	512
>>   
>> @@ -457,6 +464,7 @@ struct mmc {
>>   	int high_capacity;
>>   	uint bus_width;
>>   	uint clock;
>> +	enum mmc_voltage signal_voltage;
>>   	uint card_caps;
>>   	uint ocr;
>>   	uint dsr;
>>
>