Hi chris,
On 21 September 2011 23:36, Chris Ball <cjb@xxxxxxxxxx> wrote:
> Hi Girish,
>
> On Tue, Sep 13 2011, Girish K S wrote:
>> This patch adds the power class selection feature available
>> for mmc versions 4.0 and above.
>> During the enumeration stage before switching to the lower
>> data bus, check if the power class is supported for the
>> current bus width. If the power class is available then
>> switch to the power class and use the higher data bus. If
>> power class is not supported then switch to the lower data
>> bus in a worst case.
>>
>> Signed-off-by: Girish K S <girish.shivananjappa@xxxxxxxxxx>
>> ---
>> drivers/mmc/core/mmc.c | 77 +++++++++++++++++++++++++++++++++++++++++++++++
>> include/linux/mmc/mmc.h | 13 ++++++++
>> 2 files changed, 90 insertions(+), 0 deletions(-)
>>
>> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
>> index 63cc77b..a4004da 100644
>> --- a/drivers/mmc/core/mmc.c
>> +++ b/drivers/mmc/core/mmc.c
>> @@ -536,6 +536,81 @@ static struct device_type mmc_type = {
>> };
>>
>> /*
>> + * Select the PowerClass for the current bus width
>> + * If power class is defined for 4/8 bit bus in the
>> + * extended CSD register, select it by executing the
>> + * mmc_switch command.
>> + */
>> +static int mmc_select_powerclass(struct mmc_card *card, unsigned int bus_width)
>> +{
>> + u8 *ext_csd;
>> + int err;
>> + unsigned int pwrclass_val;
>> + unsigned int index = 0;
>> + struct mmc_host *host = card->host;
>> +
>> + BUG_ON(!card);
>> + BUG_ON(!host);
>> +
>> + /* Power class selection is supported for versions >= 4.0 */
>> + if (card->csd.mmca_vsn < CSD_SPEC_VER_4)
>> + return 0;
>> + /*Power class values are defined only for 4/8 bit bus*/
>
> Spaces between /* */ and the comment itself, please.
OK
>
>> + if (bus_width == EXT_CSD_BUS_WIDTH_1)
>> + return 0;
>> +
>> + switch ((1 << host->ios.vdd)) {
>
> Extra parens unnecessary.
OK
>
>> + case MMC_VDD_165_195:
>> + if (host->ios.clock <= 26000000)
>> + index = EXT_CSD_PWR_CL_26_195;
>> + else if (host->ios.clock <= 52000000)
>> + index = (bus_width <= EXT_CSD_BUS_WIDTH_8) ?
>> + EXT_CSD_PWR_CL_52_195 :
>> + EXT_CSD_PWR_CL_DDR_52_195;
>> + else if (host->ios.clock <= 200000000)
>> + index = EXT_CSD_PWR_CL_200_195;
>> + break;
>> + case MMC_VDD_32_33:
>> + case MMC_VDD_33_34:
>> + case MMC_VDD_34_35:
>> + case MMC_VDD_35_36:
>> + if (host->ios.clock <= 26000000)
>> + index = EXT_CSD_PWR_CL_26_360;
>> + else if (host->ios.clock <= 52000000)
>> + index = (bus_width <= EXT_CSD_BUS_WIDTH_8) ?
>> + EXT_CSD_PWR_CL_52_360 :
>> + EXT_CSD_PWR_CL_DDR_52_360;
>> + else if (host->ios.clock <= 200000000)
>> + index = EXT_CSD_PWR_CL_200_360;
>> + break;
>> + default:
>> + BUG();
>
> BUG() is a huge deal -- it will take out the entire MMC stack, so it's
> not appropriate here. How about just a pr_error() that notes an
> unexpected VDD and then returns an error value?
Will change it
>
>> + break;
>> + }
>> +
>> + err = mmc_get_ext_csd(card, &ext_csd);
>> + if (err)
>> + goto ret;
>> +
>> + pwrclass_val = ext_csd[index];
>> +
>> + if (bus_width & (EXT_CSD_BUS_WIDTH_8 | EXT_CSD_DDR_BUS_WIDTH_8))
>> + pwrclass_val = (pwrclass_val & EXT_CSD_PWR_CL_8BIT_MASK) >>
>> + EXT_CSD_PWR_CL_8BIT_SHIFT;
>> + else
>> + pwrclass_val = (pwrclass_val & EXT_CSD_PWR_CL_4BIT_MASK) >>
>> + EXT_CSD_PWR_CL_4BIT_SHIFT;
>> +
>> + err = mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
>> + EXT_CSD_POWER_CLASS,
>> + pwrclass_val,
>> + 0);
>> +ret:
>> + mmc_free_ext_csd(ext_csd);
>> + return err;
>> +}
>> +
>> +/*
>> * Handle the detection and initialisation of a card.
>> *
>> * In the case of a resume, "oldcard" will contain the card
>> @@ -802,6 +877,7 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
>> bus_width = bus_widths[idx];
>> if (bus_width == MMC_BUS_WIDTH_1)
>> ddr = 0; /* no DDR for 1-bit width */
>> + mmc_select_powerclass(card, ext_csd_bits[idx][0]);
>
> Since you're returning a meaningful error value above, we should do
> something with it here -- if you don't expect the error cases to be
> hit, you could pr_warning() the return value here so that we can
> investigate.
This patch is the first version. If you check the V2 its already handled.
>
> Thanks,
>
> - Chris.
> --
> Chris Ball <cjb@xxxxxxxxxx> <http://printf.net/>
> One Laptop Per Child
>
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