linux-kernel - Re: [PATCH v1] arm64: dts: rk3399: i2s: switch BCLK to GPIO

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Date:   Thu, 14 Jul 2022 11:14:37 -0700
From:   Brian Norris <briannorris@...omium.org>
To:     Judy Hsiao <judyhsiao@...omium.org>
Cc:     Heiko Stuebner <heiko@...ech.de>,
        Liam Girdwood <lgirdwood@...il.com>,
        Lin Huang <hl@...k-chips.com>,
        Elaine Zhang <zhangqing@...k-chips.com>,
        Shunqian Zheng <zhengsq@...k-chips.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Brown <broonie@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Chen-Yu Tsai <wenst@...omium.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
        Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1] arm64: dts: rk3399: i2s: switch BCLK to GPIO

On Fri, Jul 8, 2022 at 1:07 AM Judy Hsiao <judyhsiao@...omium.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@...omium.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@...omium.org>