linux-kernel - Re: [PATCH] arm64: dts: rockchip: Assign a fixed index to mmc devices on rk3399-roc-pc boards.

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Date:   Wed, 4 Nov 2020 07:42:01 -0800
From:   Doug Anderson <dianders@...omium.org>
To:     Heiko Stübner <heiko@...ech.de>
Cc:     "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Markus Reichl <m.reichl@...etechno.de>,
        Rob Herring <robh@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] arm64: dts: rockchip: Assign a fixed index to mmc devices
 on rk3399-roc-pc boards.

Hi,

On Wed, Nov 4, 2020 at 2:51 AM Heiko Stübner <heiko@...ech.de> wrote:
>
> Hi Markus,
>
> Am Mittwoch, 4. November 2020, 10:49:45 CET schrieb Markus Reichl:
> > Recently introduced async probe on mmc devices can shuffle block IDs.
> > Pin them to fixed values to ease booting in evironments where UUIDs
> > are not practical. Use newly introduced aliases for mmcblk devices from [1].
> >
> > [1]
> > https://patchwork.kernel.org/patch/11747669/
> >
> > Signed-off-by: Markus Reichl <m.reichl@...etechno.de>
> > ---
> >  arch/arm64/boot/dts/rockchip/rk3399-roc-pc.dtsi | 5 +++++
> >  1 file changed, 5 insertions(+)
> >
> > diff --git a/arch/arm64/boot/dts/rockchip/rk3399-roc-pc.dtsi b/arch/arm64/boot/dts/rockchip/rk3399-roc-pc.dtsi
> > index e7a459fa4322..bc9482b59428 100644
> > --- a/arch/arm64/boot/dts/rockchip/rk3399-roc-pc.dtsi
> > +++ b/arch/arm64/boot/dts/rockchip/rk3399-roc-pc.dtsi
> > @@ -13,6 +13,11 @@ / {
> >       model = "Firefly ROC-RK3399-PC Board";
> >       compatible = "firefly,roc-rk3399-pc", "rockchip,rk3399";
> >
> > +     aliases {
> > +             mmc0 = &sdmmc;
> > +             mmc1 = &sdhci;
> > +     };
> > +
>
> Any reason for this odering?
>
> I.e. some previous incarnations had it ordered as (emmc, mmc, sdio).
> This is also true for the ChromeOS out-of-tree usage of those, the
> rk3399 dts in the chromeos-4.4 tree also orders this as sdhci, sdmmc, sdio.
>
> And I guess a further question would be when we're doing arbitary orderings
> anyway, why is this not in rk3399.dtsi ;-) ?

Though I personally like the idea of eMMC, which is typically
built-in, as being the "0" number, I'm personally happy with any
numbering scheme that's consistent.  Ordering them by base address is
OK w/ me and seems less controversial.  That seems like it could go in
rk3399.dtsi and then if a particular board wanted a different order
they could override it in their board file.  The downside of putting
in rk3399 is that boards that don't have all SD/MMC interfaces enabled
would definitely get a new number compared to old kernels, but
hopefully this is the last time?

-Doug