On 15 December 2011 09:28, Girish K S <girish.shivananjappa@xxxxxxxxxx> wrote:
> This patch adds a check whether the host supports maximum current value
> obtained from the device's extended csd register for a selected interface
> voltage and frequency.
>
> cc: Chris Ball <cjb@xxxxxxxxxx>
> Signed-off-by: Girish K S <girish.shivananjappa@xxxxxxxxxx>
> ---
> Changes in v2:
> deleted a unnecessary if else condition identified by subhash J
> Changes in v1:
> reduced the number of comparisons as per Hein's suggestion
>
> drivers/mmc/core/mmc.c | 19 +++++++++++++++++++
> include/linux/mmc/card.h | 4 ++++
> 2 files changed, 23 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
> index 006e932..b9ef777 100644
> --- a/drivers/mmc/core/mmc.c
> +++ b/drivers/mmc/core/mmc.c
> @@ -688,6 +688,25 @@ static int mmc_select_powerclass(struct mmc_card *card,
> pwrclass_val = (pwrclass_val & EXT_CSD_PWR_CL_4BIT_MASK) >>
> EXT_CSD_PWR_CL_4BIT_SHIFT;
>
> + if (pwrclass_val >= MMC_MAX_CURRENT_800)
> + pwrclass_val = MMC_MAX_CURRENT_800;
> + else if (pwrclass_val >= MMC_MAX_CURRENT_600)
> + pwrclass_val = MMC_MAX_CURRENT_600;
> + else if (pwrclass_val >= MMC_MAX_CURRENT_400)
> + pwrclass_val = MMC_MAX_CURRENT_400;
> + else
> + pwrclass_val = MMC_MAX_CURRENT_200;
> +
> + if ((pwrclass_val == MMC_MAX_CURRENT_800) &&
> + !(card->host->caps & MMC_CAP_MAX_CURRENT_800))
> + pwrclass_val = MMC_MAX_CURRENT_600;
> + if ((pwrclass_val == MMC_MAX_CURRENT_600) &&
> + !(card->host->caps & MMC_CAP_MAX_CURRENT_600))
> + pwrclass_val = MMC_MAX_CURRENT_400;
> + if ((pwrclass_val == MMC_MAX_CURRENT_400) &&
> + !(card->host->caps & MMC_CAP_MAX_CURRENT_400))
> + pwrclass_val = MMC_MAX_CURRENT_200;
> +
> /* If the power class is different from the default value */
> if (pwrclass_val > 0) {
> err = mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
It is not allowed to set the POWER_CLASS with any value other than
what is mentioned in the PWR_CL_ff_vvv or PWR_CL_DDR_ff_vvv for the
corresponding frequency, voltage. That is, if PWR_CL_200_195 is 14 and
we want to operate at HS200 then the only value allowed for
POWER_CLASS is 14. So, we need to check the PWR_CL numbers and choose
the operating mode (HS200/DDR50/..) based on the platform capability
to support the current consumption and set the corresponding
POWER_CLASS value.
Please refer to section 6.6.5 of the 4.5 spec.
> diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
> index 9478a6b..c5e031a 100644
> --- a/include/linux/mmc/card.h
> +++ b/include/linux/mmc/card.h
> @@ -195,6 +195,10 @@ struct mmc_part {
> #define MMC_BLK_DATA_AREA_GP (1<<2)
> };
>
> +#define MMC_MAX_CURRENT_200 (0)
> +#define MMC_MAX_CURRENT_400 (7)
> +#define MMC_MAX_CURRENT_600 (11)
> +#define MMC_MAX_CURRENT_800 (13)
> /*
> * MMC device
> */
> --
> 1.7.1
>
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