linux-kernel - Re: [PATCH 1/2] soc: samsung: exynos-pmu: instantiate clkout driver as MFD

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Date:   Fri, 23 Oct 2020 13:37:28 +0200
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Sylwester Nawrocki <snawrocki@...nel.org>
Cc:     Tomasz Figa <tomasz.figa@...il.com>, linux-clk@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Sylwester Nawrocki <s.nawrocki@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, Kukjin Kim <kgene@...nel.org>,
        linux-samsung-soc@...r.kernel.org,
        Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: [PATCH 1/2] soc: samsung: exynos-pmu: instantiate clkout driver
 as MFD

On Fri, Oct 23, 2020 at 01:34:19PM +0200, Sylwester Nawrocki wrote:
> Hi,
> 
> On 10/1/20 18:56, Krzysztof Kozlowski wrote:
> > The Exynos clock output (clkout) driver uses same register address space
> > (Power Management Unit address space) as Exynos PMU driver and same set
> > of compatibles.  It was modeled as clock provider instantiated with
> > CLK_OF_DECLARE_DRIVE().
> > 
> > This however brings ordering problems and lack of probe deferral,
> > therefore clkout driver should be converted to a regular module and
> > instantiated as a child of PMU driver to be able to use existing
> > compatibles and address space.
> 
> It might have been cleaner to have the CLKOUT device as a PMU subnode in DT, 
> then device instantiation would be already covered by devm_of_platform_populate().
> But it gets a bit complicated to make such a change in a backward compatible way.

Yes, I agree, but the backward compatibility would be here a pain.
Optionally the driver could check for new DTB and skip adding MFD
children... but this is just simpler.

> 
> I have tested both patches on Trats2, where CLKOUT provides master clock for
> the audio codec.
> 
> Reviewed-by: Sylwester Nawrocki <s.nawrocki@...sung.com>
> Tested-by: Sylwester Nawrocki <s.nawrocki@...sung.com>

Thanks!

Best regards,
Krzysztof