Re: [PATCH v3 09/15] ASoC: tegra: Add fallback for audio mclk

[Dmitry Osipenko]

09.12.2019 23:47, Mark Brown ÐÐÑÐÑ:
> On Mon, Dec 09, 2019 at 11:31:59PM +0300, Dmitry Osipenko wrote:
>> 09.12.2019 19:40, Mark Brown ÐÐÑÐÑ:
> 
>>> Why would this need to be a stable fix?  Presumably people with stable
>>> kernels are using the old device tree anyway?
> 
>> At least Rob Herring is asking to maintain backwards compatibility
>> because some ditros are using newer device-trees with stable kernels.
> 
> You're talking about forwards compatibility not backwards here.  Are
> those distros actually using LTS kernels?

I think openSUSE Leap could be one of those distros that use LTS kernel
with newer device-trees, but that's not 100%. Maybe Rob could help
clarifying that.

>> 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.
> 
> That really does sound like a "you broke it, you get all the pieces"
> situation TBH...  I'd be a lot more comfortable if the stable kernels
> were sticking to bugfix only though I do appreciate that they're not
> really that any more.

In some cases it could be painful to maintain device-tree compatibility
for platforms like NVIDIA Tegra SoCs because hardware wasn't modeled
correctly from the start.

I agree that people should use relevant device-trees. It's quite a lot
of hassle to care about compatibility for platforms that are permanently
in a development state. It could be more reasonable to go through the
pain if kernel required a full-featured device tree for every SoC from
the start.

But maybe Tegra / device-tree maintainers have a different opinion.
IIUC, device-trees are meant to be stable and software-agnostic, at
least that was the case not so long time ago and I don't think that this
premise changed.