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Subject: Re: [PATCH v3 09/15] ASoC: tegra: Add fallback for audio mclk
To:     Mark Brown <broonie@kernel.org>,
        Sowjanya Komatineni <skomatineni@nvidia.com>
Cc:     thierry.reding@gmail.com, jonathanh@nvidia.com,
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        devicetree@vger.kernel.org, linux-clk@vger.kernel.org,
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        lgirdwood@gmail.com, perex@perex.cz, tiwai@suse.com,
        alexios.zavras@intel.com, alsa-devel@alsa-project.org
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 <20191209164027.GG5483@sirena.org.uk>
From:   Dmitry Osipenko <digetx@gmail.com>
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Date:   Mon, 9 Dec 2019 23:31:59 +0300
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09.12.2019 19:40, Mark Brown пишет:
> On Thu, Dec 05, 2019 at 06:48:49PM -0800, Sowjanya Komatineni wrote:
>> mclk is from clk_out_1 which is part of Tegra PMC block and pmc clocks
>> are moved to Tegra PMC driver with pmc as clock provider and using pmc
>> clock ids.
>>
>> New device tree uses clk_out_1 from pmc clock provider.
>>
>> So, this patch adds fallback to extern1 in case of retrieving mclk fails
>> to be backward compatible of new device tree with older kernels.
>>
>> Cc: stable@vger.kernel.org
> 
> Why would this need to be a stable fix?  Presumably people with stable
> kernels are using the old device tree anyway?
> 

Presumably, yes.

At least Rob Herring is asking to maintain backwards compatibility
because some ditros are using newer device-trees with stable kernels.
I'm personally also tending to use the newer DTB with older kernel
version whenever there is a need to check something using stable kernel.
Perhaps losing sound is not very important, but will be nicer if that
doesn't happen.