linux-kernel - Re: [PATCH] mmc: sdhci-xenon: fix 1.8v regulator stabilization

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Message-ID: <CAPv3WKc4MFeLgnJMWx=YNT5Ta5yi6fVhb4f-Rf211FTEmkvyog@mail.gmail.com>
Date:   Mon, 14 Mar 2022 16:51:25 +0100
From:   Marcin Wojtas <mw@...ihalf.com>
To:     Pali Rohár <pali@...nel.org>
Cc:     Ulf Hansson <ulf.hansson@...aro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        Ziji Hu <huziji@...vell.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Grzegorz Jaszczyk <jaz@...ihalf.com>,
        Tomasz Nowicki <tn@...ihalf.com>,
        Kostya Porotchkin <kostap@...vell.com>,
        Alex Leibovich <alexl@...vell.com>,
        "# 4.0+" <stable@...r.kernel.org>
Subject: Re: [PATCH] mmc: sdhci-xenon: fix 1.8v regulator stabilization

Hi Pali,


pon., 14 mar 2022 o 16:40 Pali Rohár <pali@...nel.org> napisał(a):
>
> On Monday 11 January 2021 19:06:24 Ulf Hansson wrote:
> > On Fri, 11 Dec 2020 at 15:17, Marcin Wojtas <mw@...ihalf.com> wrote:
> > >
> > > From: Alex Leibovich <alexl@...vell.com>
> > >
> > > Automatic Clock Gating is a feature used for the power
> > > consumption optimisation. It turned out that
> > > during early init phase it may prevent the stable voltage
> > > switch to 1.8V - due to that on some platfroms an endless
> > > printout in dmesg can be observed:
> > > "mmc1: 1.8V regulator output did not became stable"
> > > Fix the problem by disabling the ACG at very beginning
> > > of the sdhci_init and let that be enabled later.
> > >
> > > Fixes: 3a3748dba881 ("mmc: sdhci-xenon: Add Marvell Xenon SDHC core functionality")
> > > Signed-off-by: Alex Leibovich <alexl@...vell.com>
> > > Signed-off-by: Marcin Wojtas <mw@...ihalf.com>
> > > Cc: stable@...r.kernel.org
> >
> > Applied for fixes (by fixing the typos), thanks!
>
> Hello!
>
> Is not this patch address same issue which was fixed by patch which was
> merged earlier?
>
> bb32e1987bc5 ("mmc: sdhci-xenon: fix annoying 1.8V regulator warning")
> https://lore.kernel.org/linux-mmc/CAPDyKFqAsvgAjfL-c9ukFNWeGJmufQosR2Eg9SKjXMVpNitdkA@mail.gmail.com/
>

This indeed look similar. This fix was originally developed for CN913x
platform without the mentioned patch (I'm wondering if it would also
suffice to fix A3k board's problem). Anyway, I don't think we have an
issue here, as everything seems to work fine on top of mainline Linux
with both changes.

Best regards,
Marcin

> > Kind regards
> > Uffe
> >
> >
> > > ---
> > >  drivers/mmc/host/sdhci-xenon.c | 7 ++++++-
> > >  1 file changed, 6 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/mmc/host/sdhci-xenon.c b/drivers/mmc/host/sdhci-xenon.c
> > > index c67611fdaa8a..4b05f6fdefb4 100644
> > > --- a/drivers/mmc/host/sdhci-xenon.c
> > > +++ b/drivers/mmc/host/sdhci-xenon.c
> > > @@ -168,7 +168,12 @@ static void xenon_reset_exit(struct sdhci_host *host,
> > >         /* Disable tuning request and auto-retuning again */
> > >         xenon_retune_setup(host);
> > >
> > > -       xenon_set_acg(host, true);
> > > +       /*
> > > +        * The ACG should be turned off at the early init time, in order
> > > +        * to solve a possile issues with the 1.8V regulator stabilization.
> > > +        * The feature is enabled in later stage.
> > > +        */
> > > +       xenon_set_acg(host, false);
> > >
> > >         xenon_set_sdclk_off_idle(host, sdhc_id, false);
> > >
> > > --
> > > 2.29.0
> > >