Re: io-domain voltages as regulators?

From: Doug Anderson
Date: Tue Aug 12 2014 - 11:13:46 EST


On Mon, Aug 11, 2014 at 5:46 AM, Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote:
> On 11 August 2014 09:44, Linus Walleij <linus.walleij@xxxxxxxxxx> wrote:
>> On Mon, Aug 4, 2014 at 12:18 AM, Heiko StÃbner <heiko@xxxxxxxxx> 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.
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