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 > -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html