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

[Jaehoon Chung]

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?

Why didn't try to set the 1.2 voltage?

>  	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;
>