linux-kernel - Re: [PATCH v6 4/5] mfd: tps6586x: use devm-based power off handler

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Message-ID: <CAJpcXm6p4xL8XGfxbfKf8sXd6Qh8euO5FiWqhzqiLbaeYpe85g@mail.gmail.com>
Date:   Thu, 18 May 2023 13:15:22 +0200
From:   Benjamin Bara <bbara93@...il.com>
To:     Lee Jones <lee@...nel.org>
Cc:     Wolfram Sang <wsa@...nel.org>, rafael.j.wysocki@...el.com,
        dmitry.osipenko@...labora.com, peterz@...radead.org,
        jonathanh@...dia.com, richard.leitner@...ux.dev,
        treding@...dia.com, linux-kernel@...r.kernel.org,
        linux-i2c@...r.kernel.org, linux-tegra@...r.kernel.org,
        Benjamin Bara <benjamin.bara@...data.com>
Subject: Re: [PATCH v6 4/5] mfd: tps6586x: use devm-based power off handler

On Thu, 18 May 2023 at 11:43, Lee Jones <lee@...nel.org> wrote:
> Do the 2 MFD patches depend on the others?

They depend on 3/5, which is an extension to [1] and makes the
respective device available to its sys-off handler.

1/5 and 2/5 avoid a warning which is shown if the handler is called from
an emergency restart (e.g. panic()). The reason behind it is that the
i2c transfer currently doesn't recognize that it should be atomic in
this phase and utilizes the DMA instead, which schedules out while
waiting for completion ("Voluntary context switch within RCU read-side
critical section!").

[1] https://lore.kernel.org/lkml/20220509233235.995021-4-dmitry.osipenko@collabora.com/