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Subject: Re: [PATCH 2/2] clk: samsung: exynos-clkout: convert to module driver
To:     Krzysztof Kozlowski <krzk@kernel.org>,
        Tomasz Figa <tomasz.figa@gmail.com>, linux-clk@vger.kernel.org
Cc:     Sylwester Nawrocki <s.nawrocki@samsung.com>,
        Chanwoo Choi <cw00.choi@samsung.com>,
        Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@kernel.org>, Kukjin Kim <kgene@kernel.org>,
        linux-samsung-soc@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        Marek Szyprowski <m.szyprowski@samsung.com>
References: <20201001165646.32279-1-krzk@kernel.org>
 <20201001165646.32279-3-krzk@kernel.org>
From:   Sylwester Nawrocki <snawrocki@kernel.org>
Message-ID: <d84ea240-5bb7-1b77-b287-c2bcca971201@kernel.org>
Date:   Fri, 23 Oct 2020 13:42:25 +0200
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On 10/1/20 18:56, Krzysztof Kozlowski wrote:
> The Exynos clkout driver depends on board input clock (typically XXTI or
> XUSBXTI), however on Exynos4 boards these clocks were modeled as part of
> SoC clocks (Exynos4 clocks driver).  Obviously this is not proper, but
> correcting it would break DT backward compatibility.
> 
> Both drivers - clkout and Exynos4 clocks - register the clock providers
> with CLK_OF_DECLARE/OF_DECLARE_1 so their order is fragile (in the
> Makefile clkout is behind Exynos4 clock).  It will work only if the
> Exynos4 clock driver comes up before clkout.
> 
> A change in DTS adding input clock reference to Exynos4 clocks input
> PLL, see reverted commit eaf2d2f6895d ("ARM: dts: exynos: add input
> clock to CMU in Exynos4412 Odroid"), caused probe reorder: the clkout
> appeared before Exynos4 clock provider.  Since clkout depends on Exynos4
> clocks and does not support deferred probe, this did not work and caused
> later failure of usb3503 USB hub probe which needs clkout:
> 
>      [    5.007442] usb3503 0-0008: unable to request refclk (-517)
> 
> The Exynos clkout driver is not a critical/core clock so there is
> actually no problem in instantiating it later, as a regular module.
> This removes specific probe ordering and adds support for probe
> deferral.


The patch looks good to me, I have tested it on Trats2, where CLKOUT
provides master clock for the audio codec.

Tested-by: Sylwester Nawrocki <s.nawrocki@samsung.com>

With the debug print removed feel free to apply it through your tree.
Reviewed-by: Sylwester Nawrocki <s.nawrocki@samsung.com>

--
Regards,
Sylwester