linux-kernel - Re: [PATCH v2 3/3] riscv: dts: starfive: Add mmc node

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Message-ID: <CAPDyKFrH=U-Sz1Kx2AJ+X_FXi9GcEdHXjO+aC=MXpGP_+xgOsQ@mail.gmail.com>
Date:   Wed, 4 Jan 2023 17:05:50 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     William Qiu <william.qiu@...rfivetech.com>
Cc:     linux-riscv@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-mmc@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Jaehoon Chung <jh80.chung@...sung.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/3] riscv: dts: starfive: Add mmc node

On Wed, 4 Jan 2023 at 07:08, William Qiu <william.qiu@...rfivetech.com> wrote:
>
>
>
> On 2023/1/2 22:03, Ulf Hansson wrote:
> > On Tue, 27 Dec 2022 at 13:22, William Qiu <william.qiu@...rfivetech.com> wrote:
> >>
> >> This adds the mmc node for the StarFive JH7110 SoC.
> >> Set sdioo node to emmc and set sdio1 node to sd.
> >>
> >> Signed-off-by: William Qiu <william.qiu@...rfivetech.com>
> >> ---
> >>  .../jh7110-starfive-visionfive-v2.dts         | 25 ++++++++++++
> >>  arch/riscv/boot/dts/starfive/jh7110.dtsi      | 38 +++++++++++++++++++
> >>  2 files changed, 63 insertions(+)
> >>
> >> diff --git a/arch/riscv/boot/dts/starfive/jh7110-starfive-visionfive-v2.dts b/arch/riscv/boot/dts/starfive/jh7110-starfive-visionfive-v2.dts
> >> index c8946cf3a268..d8244fd1f5a0 100644
> >> --- a/arch/riscv/boot/dts/starfive/jh7110-starfive-visionfive-v2.dts
> >> +++ b/arch/riscv/boot/dts/starfive/jh7110-starfive-visionfive-v2.dts
> >> @@ -47,6 +47,31 @@ &clk_rtc {
> >>         clock-frequency = <32768>;
> >>  };
> >>
> >> +&mmc0 {
> >> +       max-frequency = <100000000>;
> >> +       card-detect-delay = <300>;
> >
> > Nitpick:  This seems redundant for a non-removable card!?
> >
>
> Will drop
>
> >> +       bus-width = <8>;
> >> +       cap-mmc-highspeed;
> >> +       mmc-ddr-1_8v;
> >> +       mmc-hs200-1_8v;
> >> +       non-removable;
> >> +       cap-mmc-hw-reset;
> >> +       post-power-on-delay-ms = <200>;
> >> +       status = "okay";
> >> +};
> >> +
> >> +&mmc1 {
> >> +       max-frequency = <100000000>;
> >> +       card-detect-delay = <300>;
> >
> > Nitpick: This looks redundant for polling based card detection
> > (broken-cd is set a few lines below).
> >
>
> Will drop
>
> >> +       bus-width = <4>;
> >> +       no-sdio;
> >> +       no-mmc;
> >> +       broken-cd;
> >> +       cap-sd-highspeed;
> >> +       post-power-on-delay-ms = <200>;
> >> +       status = "okay";
> >> +};
> >> +
> >>  &gmac0_rmii_refin {
> >>         clock-frequency = <50000000>;
> >>  };
> >> diff --git a/arch/riscv/boot/dts/starfive/jh7110.dtsi b/arch/riscv/boot/dts/starfive/jh7110.dtsi
> >> index c22e8f1d2640..08a780d2c0f4 100644
> >> --- a/arch/riscv/boot/dts/starfive/jh7110.dtsi
> >> +++ b/arch/riscv/boot/dts/starfive/jh7110.dtsi
> >> @@ -331,6 +331,11 @@ aoncrg: clock-controller@...00000 {
> >>                         #reset-cells = <1>;
> >>                 };
> >>
> >> +               syscon: syscon@...30000 {
> >> +                       compatible = "starfive,syscon", "syscon";
> >> +                       reg = <0x0 0x13030000 0x0 0x1000>;
> >> +               };
> >> +
> >>                 gpio: gpio@...40000 {
> >>                         compatible = "starfive,jh7110-sys-pinctrl";
> >>                         reg = <0x0 0x13040000 0x0 0x10000>;
> >> @@ -433,5 +438,38 @@ uart5: serial@...20000 {
> >>                         reg-shift = <2>;
> >>                         status = "disabled";
> >>                 };
> >> +
> >> +               /* unremovable emmc as mmcblk0 */
> >
> > Don't confuse the mmc0 node name with mmcblk0. There is no guarantee
> > that this is true, unless you also specify an alias.
> >
>
> Hi Ulf,
>
> Thank you for taking time to review and provide helpful comments for this patch.
> Actually we define mmc0 as eMMC, which is mmcblk0 in the kernel, and define mmc1 as SDIO,
> which is mmcblk1 in the kernel, so it's not confuse.
>

My point is, mmc0 from DT node perspective doesn't necessarily need to
map to mmc0, as that depends on the "probe" order of the devices. At
least for the Linux kernel, mmc0 from DT point of view, could end up
being mmc1.

To avoid confusion, please drop the "mmcblk*" here. It's anyway a
Linux specific thing. Don't get me wrong, feel free to keep the
information about eMMC and SDIO for the corresponding mmc controller
node.

Moreover, if you can't use PARTID/UUID to find the rootfs device -
then you may use an aliases node, to let mmc0 to be enumerated as
mmc0, for example. See below.

aliases {
     mmc0 = &mmc0;
}

Kind regards
Uffe