linux-kernel - Re: [PATCH] mmc: meson: initial ocr available by default value

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Message-ID: <CAFBinCCr9RQReHOJbb=spcVRxM0aRo=Z3YMz_zxA_qiFBDzwWA@mail.gmail.com>
Date:   Mon, 13 Dec 2021 09:00:16 +0100
From:   Martin Blumenstingl <martin.blumenstingl@...glemail.com>
To:     Rong Chen <rong.chen@...ogic.com>
Cc:     Ulf Hansson <ulf.hansson@...aro.org>,
        Neil Armstrong <narmstrong@...libre.com>,
        Kevin Hilman <khilman@...libre.com>,
        Jerome Brunet <jbrunet@...libre.com>, --to=1131046452@...com,
        45581586@...com, linux-mmc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-amlogic@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mmc: meson: initial ocr available by default value

Hello,

On Mon, Dec 13, 2021 at 8:03 AM Rong Chen <rong.chen@...ogic.com> wrote:
>
> The patch will add a value of ocr supported by the controller,
> to specify some of voltage values are supported.
Can you please share some details on this topic?

We already have many boards upstreamed which work fine without
manually setting ocr_avail in the driver.
In general there's two types of boards:
1) boards where the regulator can switch between different voltages.
One example is the Odroid-C2, see meson-gxbb-odroidc2.dts [0]
Here we specify:
  vmmc-supply = <&tflash_vdd>;
  vqmmc-supply = <&tf_io>;
&tflash_vdd is either turned off or at 3.3V when turned on.
&tf_io can be either turned off, 1.8V or 3.3V.

2) boards where the voltages are fixed.
One example is Radxa Zero, see meson-g12a-radxa-zero.dts [1]
For the SD card the board uses:
  vmmc-supply = <&vddao_3v3>;
  vqmmc-supply = <&vddao_3v3>;
(meaning fixed 3.3V always-on power source for both VMMC and VQMMC)
and for eMMC the board uses:
  vmmc-supply = <&vcc_3v3>;
  vqmmc-supply = <&vcc_1v8>;
(meaning: 3.3V always-on power source for vmmc and 1.8V always-on
power source for VQMMC)

With the information from the regulators the MMC core will
automatically detect ocr_avail in Linux.
Or in other words: your .dts may be missing the link between regulator
and MMC controller vmmc/vqmmc.
Can you please double-check this?

Best regards,
Martin

[0] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/boot/dts/amlogic/meson-gxbb-odroidc2.dts?id=2585cf9dfaaddf00b069673f27bb3f8530e2039c#n354
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/boot/dts/amlogic/meson-g12a-radxa-zero.dts?id=2585cf9dfaaddf00b069673f27bb3f8530e2039c#n333