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References: <20220822074139.3810-1-jensenhuang@friendlyarm.com> <23552842.6Emhk5qWAg@diego>
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From:   Doug Anderson <dianders@chromium.org>
Date:   Tue, 23 Aug 2022 07:13:06 -0700
Message-ID: <CAD=FV=W-ajJDfYcP3P8Jyk_KgsUAbdTtmwiNXqJ=Ab2ojgrUGw@mail.gmail.com>
Subject: Re: [PATCH] arm64: dts: rockchip: add enable-strobe-pulldown to emmc
 phy on rk3399
To:     =?UTF-8?Q?Heiko_St=C3=BCbner?= <heiko@sntech.de>
Cc:     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>,
        Jensen Huang <jensenhuang@friendlyarm.com>,
        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,

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 disabled
> > 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 dt=
s")
> > 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