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From:   Peter Geis <pgwipeout@gmail.com>
Date:   Thu, 5 Aug 2021 08:58:58 -0400
Message-ID: <CAMdYzYpR6br7s1RD2ze92WzJjtEDZwy9qS6YhghgXy7F91keFg@mail.gmail.com>
Subject: Re: [BUG] mmc_regulator_set_ocr can't cope with regulator-fixed
To:     Mark Brown <broonie@kernel.org>
Cc:     Jaehoon Chung <jh80.chung@samsung.com>,
        Ulf Hansson <ulf.hansson@linaro.org>,
        Liam Girdwood <lgirdwood@gmail.com>,
        Rob Herring <robh+dt@kernel.org>, linux-mmc@vger.kernel.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@lists.infradead.org>,
        devicetree@vger.kernel.org
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On Thu, Aug 5, 2021 at 8:47 AM Mark Brown <broonie@kernel.org> wrote:
>
> On Thu, Aug 05, 2021 at 07:38:06AM -0400, Peter Geis wrote:
>
> > Also, I've got a possible fix to the dw-mmc issue, the following patch
> > changes the behavior to only enable a fixed regulator, not try to set
> > the voltage. It's a split between the behavior when vmmc isn't defined
> > at all and when its a variable regulator:
>
> One thing to watch out for with this approach is if there's things that
> really need a specific voltage to be set then you'll have to stop those
> things happening if you've got a voltage regulator that can't deliver a
> voltage in the required range.  I don't know if this affects MMC or not,
> if it's just a case of being less efficient it's not such an issue.

Yeah, but if this is a fixed regulator and it's a problem, then the
hardware is screwed anyways.

>
> > diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
> > index d333130d1531..b30102980261 100644
> > --- a/drivers/mmc/host/dw_mmc.c
> > +++ b/drivers/mmc/host/dw_mmc.c
> > @@ -1446,11 +1446,13 @@ static void dw_mci_set_ios(struct mmc_host
> > *mmc, struct mmc_ios *ios)
> >   switch (ios->power_mode) {
> >   case MMC_POWER_UP:
> >   if (!IS_ERR(mmc->supply.vmmc)) {
> > - ret = mmc_regulator_set_ocr(mmc, mmc->supply.vmmc,
>
> This patch is very whitespace damaged FWIW.

Unfortunately gmail doesn't let you reply with patch sets without
mangling them, so it's only useful as an example.
If it seems sane I'll send it as a proper patch.