[U-Boot] [PATCH 14/22] mmc: add power cyle support in mmc core

[Jean-Jacques Hiblot]

Hi Jaehoon,


On 25/05/2017 14:35, Jaehoon Chung wrote:
> On 05/13/2017 03:16 AM, Jean-Jacques Hiblot wrote:
>> mmc/sd specification requires vdd to be disabled for 1 ms
>> and then enabled again during power cycle. Add a
>> function in mmc core to perform power cycle and set
>> the io signal to it's initial state.
>>
>> 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 | 50 +++++++++++++++++++++++++++++++++++++++++---------
>>   1 file changed, 41 insertions(+), 9 deletions(-)
>>
>> diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c
>> index d40a22b..032260b 100644
>> --- a/drivers/mmc/mmc.c
>> +++ b/drivers/mmc/mmc.c
>> @@ -30,6 +30,7 @@ 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);
>> +static void mmc_power_cycle(struct mmc *mmc);
>>   
>>   #if CONFIG_IS_ENABLED(MMC_TINY)
>>   static struct mmc mmc_static;
>> @@ -1915,6 +1916,45 @@ static int mmc_power_init(struct mmc *mmc)
>>   	return 0;
>>   }
>>   
>> +static void mmc_set_initial_state(struct mmc *mmc)
>> +{
>> +	int err;
>> +
>> +	/* 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");
>> +
>> +	mmc_set_bus_width(mmc, 1);
>> +	mmc_set_clock(mmc, 1);
>> +	mmc_select_mode(mmc, MMC_LEGACY);
>> +}
>> +
>> +static void mmc_power_up(struct mmc *mmc)
>> +{
>> +	mmc_set_initial_state(mmc);
>> +	mmc_set_vdd(mmc, true);
> mmc_set_vdd has the return value..but there are no usage anywhere..
> if this is correct, mmc_set_vdd can be *void* type.
>
>> +	udelay(10000);
>> +}
>> +
>> +static void mmc_power_off(struct mmc *mmc)
>> +{
>> +	mmc_set_vdd(mmc, false);
>> +}
>> +
>> +static void mmc_power_cycle(struct mmc *mmc)
>> +{
>> +	mmc_power_off(mmc);
>> +	/*
>> +	 * SD spec recommends at least 1ms of delay. Let's wait for 2ms
>> +	 * to be on the safer side.
>> +	 */
> Could you put the SD spec version and about which part...?
> I didn't find the 2ms so..i want to see the spec about 2ms.
The requirement for 1ms is found in the simplified specifications 
"Part1_Physical_Layer_Simplified_Specification_Ver6.00.pdf":

[...]
6.4.1.5 Power Down and Power Cycle
When the host shuts down the power, the card VDD shall be lowered to 
less than 0.5Volt for a minimum period of 1ms.
[....]

2ms is just to be on the safer side.

JJ

>
>> +	udelay(2000);
>> +	mmc_power_up(mmc);
>> +}
>> +
>>   int mmc_start_init(struct mmc *mmc)
>>   {
>>   	bool no_card;
>> @@ -1952,16 +1992,8 @@ int mmc_start_init(struct mmc *mmc)
>>   		return err;
>>   #endif
>>   	mmc->ddr_mode = 0;
>> -	mmc_set_vdd(mmc, true);
>> -	/* 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");
>>   
>> -	mmc_set_bus_width(mmc, 1);
>> -	mmc_set_clock(mmc, 1);
>> +	mmc_power_cycle(mmc);
>>   
>>   	/* Reset the Card */
>>   	err = mmc_go_idle(mmc);
>>
>