Hi, On Mon, Aug 11, 2014 at 5:46 AM, Ulf Hansson <ulf.hans...@linaro.org> wrote: > On 11 August 2014 09:44, Linus Walleij <linus.wall...@linaro.org> wrote: >> On Mon, Aug 4, 2014 at 12:18 AM, Heiko Stübner <he...@sntech.de> wrote: >> >> [Adding Ulf Hansson to this discussion...] >> >>> Hi Mark, Linus, >>> >>> I'd like to clarify what the appropriate way to handle pin output voltages >>> is. >>> On the Rockchip SoCs the voltage for some groups of pins can be set between >>> 3.3V and 1.8V ... like the MMC/SD pins who need this to support UHS mode >>> cards. >> >> This is called "vqmmc" in the mmc/sd subsystem. >> >> grep for mmc_set_signal_voltage() in drivers/mmc/core/* >> >> In drivers/mmc/core/core.c, you find: >> >> mmc->supply.vqmmc = devm_regulator_get_optional(dev, "vqmmc"); >> >> Which gets the regulator to set the signal voltage, if such >> a regulator is specified for the host. >> >> Very simple and straight-forward, and handled by the MMC core. >> >>> In [0] when talking about something different, Linus Walleij described a >>> similar case as >>> >>> "I think we need to have a discussion with Mark Brown on how to >>> handle this. >>> We have previously had the case of MMC/SD level-shifters, where >>> a certain setting gives a certain level of signals out, and another setting >>> gives another level. Like two discrete levels. >>> So we modeled that as a regulator provider inside the pin control >>> driver eventually, see sh-pfc/pfc-sh73a0.c" >>> >>> As this sound like exactly the thing I'm trying to solve, is handling this >>> via >>> a regulator the correct general way? >> >> Ithinkso. > > Just to confirm, I fully agree with the above said. > > You may also find a good example in the mmci host driver for how to > make use of the vqmmc regulator.
Yuvaraj also submitted patches for dw_mmc: 4401241 New [1/3] mmc: dw_mmc: use mmc_regulator_get_supply to handle regulators 4401261 New [2/3] mmc: dw_mmc: Dont cut off vqmmc and vmmc 4401281 New [3/3] mmc: dw_mmc: Support voltage changes He seems to have dropped these patches on the floor and I had review feedback on them, but I think they're in the right direction. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
