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From:   Brian Norris <briannorris@chromium.org>
Date:   Thu, 14 Jul 2022 11:14:37 -0700
Message-ID: <CA+ASDXM-Cb8idKp+9nBDrGd5SRb4dy20TChAQT3WmdwS+wbzNw@mail.gmail.com>
Subject: Re: [PATCH v1] arm64: dts: rk3399: i2s: switch BCLK to GPIO
To:     Judy Hsiao <judyhsiao@chromium.org>
Cc:     Heiko Stuebner <heiko@sntech.de>,
        Liam Girdwood <lgirdwood@gmail.com>,
        Lin Huang <hl@rock-chips.com>,
        Elaine Zhang <zhangqing@rock-chips.com>,
        Shunqian Zheng <zhengsq@rock-chips.com>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Brown <broonie@kernel.org>,
        Jaroslav Kysela <perex@perex.cz>,
        Chen-Yu Tsai <wenst@chromium.org>,
        devicetree <devicetree@vger.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@lists.infradead.org>,
        Linux Kernel <linux-kernel@vger.kernel.org>
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On Fri, Jul 8, 2022 at 1:07 AM Judy Hsiao <judyhsiao@chromium.org> wrote:
>
> We discoverd that the state of BCLK on, LRCLK off and SD_MODE on

super-nit: s/discoverd/discovered/

(If this is the only issue, perhaps Heiko can fix that when applying.)

> may cause the speaker melting issue. Removing LRCLK while BCLK
> is present can cause unexpected output behavior including a large
> DC output voltage as described in the Max98357a datasheet.
>
> In order to:
>   1. prevent BCLK from turning on by other component.
>   2. keep BCLK and LRCLK being present at the same time
>
> This patch adjusts the device tree to allow BCLK to switch
> to GPIO func before LRCLK output, and switch back during
> LRCLK is output.
>
> Signed-off-by: Judy Hsiao <judyhsiao@chromium.org>

IIUC, it's not guaranteed everyone is using max98357a on this I2S
channel, but I suppose this change is still safe anyway? Or if this is
expected only for Gru-related boards, we could override the i2s node
settings in rk3399-gru.dtsi or similar.

Anyway, I think this is right:

Reviewed-by: Brian Norris <briannorris@chromium.org>