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From:   Jensen Huang <jensenhuang@friendlyarm.com>
Date:   Fri, 26 Aug 2022 20:03:43 +0800
Message-ID: <CAMpZ1qGya8zr-QJZHY4OqEg0NLo_db6ttnf6Ai2NHdUL1+6qBw@mail.gmail.com>
Subject: Re: [PATCH] arm64: dts: rockchip: add enable-strobe-pulldown to emmc
 phy on rk3399
To:     Doug Anderson <dianders@chromium.org>
Cc:     =?UTF-8?Q?Heiko_St=C3=BCbner?= <heiko@sntech.de>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Vinod Koul <vkoul@kernel.org>,
        Chris Ruehl <chris.ruehl@gtsys.com.hk>,
        Brian Norris <briannorris@chromium.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@lists.infradead.org>,
        LKML <linux-kernel@vger.kernel.org>
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Hi,

Thanks!
I understand that this patch does potentially affect boards with
external pull down.
To avoid this, I will move `enable-strobe-pulldown` to
rk3399-nanopi4.dtsi and send patch v2.


BR,
Jensen

On Wed, Aug 24, 2022 at 10:58 PM Doug Anderson <dianders@chromium.org> wrot=
e:
>
> Hi,
>
> On Tue, Aug 23, 2022 at 8:11 PM Jensen Huang
> <jensenhuang@friendlyarm.com> wrote:
> >
> > Hi,
> >
> > Sorry for sending an email in HTML format.
> >
> > I realized that only some devices may be affected, so I considered
> > modifying rk3399-nanopi4.dtsi only,
> > but other boards without external pull-down should still need this patc=
h.
>
> I guess the other alternative would be to change how the dt property
> works. You could say:
>
> 1. If `enable-strobe-pulldown` is set then enable the strobe pulldown.
>
> 2. If `enable-strobe-pulldown` is not set then don't touch the pin in
> the kernel.
>
> 3. If someone later needs to explicitly disable the strobe pulldown
> they could add a new property like `disable-strobe-pulldown`.
>
>
> Obviously there are tradeoffs between that and what you've done and
> I'm happy to let others make the call of which they'd prefer.
>
>
> > BR,
> > Jensen
> >
> > On Tue, Aug 23, 2022 at 10:13 PM Doug Anderson <dianders@chromium.org> =
wrote:
> > >
> > > Hi,
> > >
> > > On Tue, Aug 23, 2022 at 4:53 AM Heiko St=C3=BCbner <heiko@sntech.de> =
wrote:
> > > >
> > > > Am Montag, 22. August 2022, 09:41:39 CEST schrieb Jensen Huang:
> > > > > Internal pull-down for strobe line (GRF_EMMCPHY_CON2[9]) was disa=
bled
> > > > > by commit 8b5c2b45b8f0, which causes I/O error in HS400 mode.
> > > > >
> > > > > Tested on NanoPC-T4.
> > > > >
> > > > > Fixes: 8b5c2b45b8f0 ("phy: rockchip: set pulldown for strobe line=
 in dts")
> > > > > Signed-off-by: Jensen Huang <jensenhuang@friendlyarm.com>
> > > >
> > > > ok, so this looks like it restores previous functionality.
> > > >
> > > > I'm just wondering as the "offending" patch is from 2020, why this
> > > > only turns up now. Any ideas?
> > >
> > > Ah, I see. So before the offending patch we used to just leave the
> > > pull state at whatever the default was when the kernel was booted.
> > > After the offending patch we chose a default.
> > >
> > > On kevin I see an external pull down on this line. Enabling both the
> > > internal and external is probably not a huge deal, it'll just affect
> > > the strength of the pull.
> > >
> > > On bob I _think_ the external pull down is also stuffed.
> > >
> > > ...so I guess that would explain why it didn't cause a problem for at
> > > least those two boards?
> > >
> > > -Doug