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References: <20230118091122.2205452-1-dmitry.baryshkov@linaro.org>
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From:   Rob Herring <robh+dt@kernel.org>
Date:   Wed, 18 Jan 2023 07:35:15 -0600
Message-ID: <CAL_JsqJ=0neiZ4wkPiMqJMT4E1O_xO0uLrTmEGUcnZMqxkw4UQ@mail.gmail.com>
Subject: Re: [RESEND PATCH] of: property: do not create clocks device link for
 clock controllers
To:     Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Cc:     Frank Rowand <frowand.list@gmail.com>, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org,
        Bjorn Andersson <andersson@kernel.org>,
        Stephen Boyd <sboyd@kernel.org>,
        Saravana Kannan <saravanak@google.com>,
        Abel Vesa <abel.vesa@linaro.org>
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On Wed, Jan 18, 2023 at 3:11 AM Dmitry Baryshkov
<dmitry.baryshkov@linaro.org> wrote:
>
> Do not create device link for clock controllers. Some of the clocks
> provided to the device via OF can be the clocks that are just parents to
> the clocks provided by this clock controller. Clock subsystem already
> has support for handling missing clock parents correctly (clock
> orphans). Later when the parent clock is registered, clocks get
> populated properly.
>
> An example of the system where this matters is the SDM8450 MTP board
> (see arch/arm64/boot/dts/qcom/sdm845-mtp.dts). Here the dispcc uses
> clocks provided by dsi0_phy and dsi1_phy device tree nodes. However the
> dispcc itself provides clocks to both PHYs, to the PHY parent device,
> etc. With just dsi0_phy in place devlink is able to break the
> dependency, but with two PHYs, dispcc doesn't get probed at all, thus
> breaking display support.
>
> Cc: Bjorn Andersson <andersson@kernel.org>
> Cc: Stephen Boyd <sboyd@kernel.org>
> Cc: Saravana Kannan <saravanak@google.com>
> Cc: Abel Vesa <abel.vesa@linaro.org>
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> ---
>
> This patch has been posted a year ago in January 2022 ([1]). Since that time
> Saravana failed to produce patches to assist in debugging the issue
> ([2]) or to fix the issue ([3]). The issue we observe has been described
> by Abel at ([4]). As we work on adding support for Dual DSI
> configurations, the issue becomes more and more important, since binding
> the whole display subsystem fails.

That's ample time to fix this, so I intend to apply this. But I'll
give it a few days for comments.

Rob