linux-kernel - Re: [PATCH 01/22] clk: sunxi-ng: v3s: Make the ISP PLL clock public

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Message-ID: <20210913075417.ampb2jt4quftpqzj@gilmour>
Date:   Mon, 13 Sep 2021 09:54:17 +0200
From:   Maxime Ripard <maxime@...no.tech>
To:     Paul Kocialkowski <paul.kocialkowski@...tlin.com>
Cc:     linux-media@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-phy@...ts.infradead.org,
        linux-clk@...r.kernel.org, linux-staging@...ts.linux.dev,
        Yong Deng <yong.deng@...ewell.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Helen Koike <helen.koike@...labora.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH 01/22] clk: sunxi-ng: v3s: Make the ISP PLL clock public

On Fri, Sep 10, 2021 at 08:41:26PM +0200, Paul Kocialkowski wrote:
> In order to reparent the CSI module clock to the ISP PLL via
> device-tree, export the ISP PLL clock declaration in the public
> device-tree header.

You use clk_set_rate_exclusive in the ISP driver on the module clock so
it should prevent what you're mentioning from happening.

If it doesn't, then clk_set_rate_exclusive has a bug and should be
fixed.

Either way, using assigned-clock-parents is not a good solution here
either, it only makes sure that this is the case when probe is run.

> Details regarding why the CSI module clock is best parented to the ISP
> PLL are provided in the related commit.

This is relevant to this commit too and "the related commit" is far too
blurry when you consider the entire Linux git history.

Maxime

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