Re: [PATCH v2 07/12] mmc: sd: set current limit for uhs cards

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On Mar 4, 2011, at 3:32 AM, Arindam Nath wrote:

> We decide on the current limit to be set for the card based on the
> Capability of Host Controller to provide current at 1.8V signalling,
> and the maximum current limit of the card as indicated by CMD6
> mode 0. We then set the current limit for the card using CMD6 mode 1.
> 
> Signed-off-by: Arindam Nath <arindam.nath@xxxxxxx>
> ---
> drivers/mmc/core/sd.c    |   45 +++++++++++++++++++++++++++++++++++++++++++++
> drivers/mmc/host/sdhci.c |   24 ++++++++++++++++++++++++
> include/linux/mmc/card.h |    9 +++++++++
> include/linux/mmc/host.h |    1 +
> 4 files changed, 79 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
> index ec0d8e6..df98a2c 100644
> --- a/drivers/mmc/core/sd.c
> +++ b/drivers/mmc/core/sd.c
> @@ -550,6 +550,46 @@ static int sd_set_bus_speed_mode(struct mmc_card *card, u8 *status)
> 	return 0;
> }
> 
> +static int sd_set_current_limit(struct mmc_card *card, u8 *status)
> +{
> +	struct mmc_host *host = card->host;
> +	int mmc_host_max_current_180, current_limit;
> +	int err;
> +
> +	/* sanity check */
> +	if (!host->ops->get_max_current_180)
> +		return 0;

a better name would be get_max_current rather than get_max_current_180

do you want a test for get_max_current_180 < 400 ? and return 0  have it do the switch
by setting the value ?  
> +
> +	/* Maximum current supported by host at 1.8V */
> +	mmc_host_max_current_180 = host->ops->get_max_current_180(host);
> +
> +	if (mmc_host_max_current_180 >= 800) {
> +		if (card->sw_caps.uhs_curr_limit & SD_MAX_CURRENT_800)
> +			current_limit = SD_SET_CURRENT_LIMIT_800;
> +		else if (card->sw_caps.uhs_curr_limit & SD_MAX_CURRENT_600)
> +			current_limit = SD_SET_CURRENT_LIMIT_600;
> +		else if (card->sw_caps.uhs_curr_limit & SD_MAX_CURRENT_400)
> +			current_limit = SD_SET_CURRENT_LIMIT_400;
> +	} else if (mmc_host_max_current_180 >= 600) {
> +		if (card->sw_caps.uhs_curr_limit & SD_MAX_CURRENT_600)
> +			current_limit = SD_SET_CURRENT_LIMIT_600;
> +		else if (card->sw_caps.uhs_curr_limit & SD_MAX_CURRENT_400)
> +			current_limit = SD_SET_CURRENT_LIMIT_400;
> +	} else if (mmc_host_max_current_180 >= 400)
> +		if (card->sw_caps.uhs_curr_limit & SD_MAX_CURRENT_400)
> +			current_limit = SD_SET_CURRENT_LIMIT_400;

or
        else
               current_limit = SD_SET_CURRENT_LIMIT_200;
> +
> +	err = mmc_sd_switch(card, 1, 3, current_limit, status);
> +	if (err)
> +		return err;
> +
> +	if (((status[15] >> 4) & 0x0F) != current_limit)
> +		printk(KERN_WARNING "%s: Problem setting current limit!\n",
> +			mmc_hostname(card->host));
> +
> +	return 0;
> +}
> +
> /*
>  * UHS-I specific initialization procedure
>  */
> @@ -590,6 +630,11 @@ static int mmc_sd_init_uhs_card(struct mmc_card *card)
> 
> 	/* Set bus speed mode of the card */
> 	err = sd_set_bus_speed_mode(card, status);
> +	if (err)
> +		goto out;
> +
> +	/* Set current limit for the card */
> +	err = sd_set_current_limit(card, status);
> 
> out:
> 	kfree(status);
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index f127fa2..245cc39 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -1462,12 +1462,36 @@ static int sdhci_start_signal_voltage_switch(struct mmc_host *mmc)
> 	return -EAGAIN;
> }
> 

better name is sdhci_get_max_current

> +static int sdhci_get_max_current_180(struct mmc_host *mmc)
> +{
> +	struct sdhci_host *host;
> +	u32 max_current_caps;
> +	unsigned long flags;
> +	int max_current_180;
> +
> +	host = mmc_priv(mmc);
> +
> +	spin_lock_irqsave(&host->lock, flags);
> +
> +	max_current_caps = sdhci_readl(host, SDHCI_MAX_CURRENT);
> +
> +	spin_unlock_irqrestore(&host->lock, flags);
> +
> +	/* Maximum current is 4 times the register value for 1.8V */
> +	max_current_180 = ((max_current_caps & SDHCI_MAX_CURRENT_180_MASK) >>
> +			   SDHCI_MAX_CURRENT_180_SHIFT) *
> +			   SDHCI_MAX_CURRENT_MULTIPLIER;

 SDHCI_MAX_CURRENT_SHIFT is better name.   

> +
> +	return max_current_180;
> +}
> +
> static const struct mmc_host_ops sdhci_ops = {
> 	.request	= sdhci_request,
> 	.set_ios	= sdhci_set_ios,
> 	.get_ro		= sdhci_get_ro,
> 	.enable_sdio_irq = sdhci_enable_sdio_irq,
> 	.start_signal_voltage_switch	= sdhci_start_signal_voltage_switch,
> +	.get_max_current_180		= sdhci_get_max_current_180,

.get_max_current = sdhci_get_max_current;
> };
> 
> /*****************************************************************************\
> diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
> index 0b24c41..a6811ae 100644
> --- a/include/linux/mmc/card.h
> +++ b/include/linux/mmc/card.h
> @@ -98,6 +98,15 @@ struct sd_switch_caps {
> #define SD_DRIVER_TYPE_C	0x04
> #define SD_DRIVER_TYPE_D	0x08
> 	unsigned int		uhs_curr_limit;
> +#define SD_SET_CURRENT_LIMIT_200	0
> +#define SD_SET_CURRENT_LIMIT_400	1
> +#define SD_SET_CURRENT_LIMIT_600	2
> +#define SD_SET_CURRENT_LIMIT_800	3
> +
> +#define SD_MAX_CURRENT_200	(1 << SD_SET_CURRENT_LIMIT_200)
> +#define SD_MAX_CURRENT_400	(1 << SD_SET_CURRENT_LIMIT_400)
> +#define SD_MAX_CURRENT_600	(1 << SD_SET_CURRENT_LIMIT_600)
> +#define SD_MAX_CURRENT_800	(1 << SD_SET_CURRENT_LIMIT_800)
> };
> 
> struct sdio_cccr {
> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
> index 4dfff6d..e84cd05 100644
> --- a/include/linux/mmc/host.h
> +++ b/include/linux/mmc/host.h
> @@ -128,6 +128,7 @@ struct mmc_host_ops {
> 	void	(*init_card)(struct mmc_host *host, struct mmc_card *card);
> 
> 	int	(*start_signal_voltage_switch)(struct mmc_host *host);
> +	int	(*get_max_current_180)(struct mmc_host *mmc);
> };
> 
> struct mmc_card;
> -- 
> 1.7.1
> 

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