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From:   Heiko =?ISO-8859-1?Q?St=FCbner?= <heiko@sntech.de>
To:     Sascha Hauer <s.hauer@pengutronix.de>,
        Rob Herring <robh@kernel.org>
Cc:     dri-devel <dri-devel@lists.freedesktop.org>,
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        "open list:ARM/Rockchip SoC..." <linux-rockchip@lists.infradead.org>,
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        Sandy Huang <hjc@rock-chips.com>,
        Peter Geis <pgwipeout@gmail.com>
Subject: Re: [PATCH 08/22] dt-bindings: display: rockchip: dw-hdmi: use "ref" as clock name
Date:   Wed, 22 Dec 2021 20:39:58 +0100
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Am Mittwoch, 22. Dezember 2021, 14:52:51 CET schrieb Rob Herring:
> On Wed, Dec 22, 2021 at 6:47 AM Sascha Hauer <s.hauer@pengutronix.de> wrote:
> >
> > On Tue, Dec 21, 2021 at 10:31:23AM -0400, Rob Herring wrote:
> > > On Mon, Dec 20, 2021 at 12:06:16PM +0100, Sascha Hauer wrote:
> > > > "vpll" is a misnomer. A clock input to a device should be named after
> > > > the usage in the device, not after the clock that drives it. On the
> > > > rk3568 the same clock is driven by the HPLL.
> > > > To fix that, this patch renames the vpll clock to ref clock.
> > >
> > > The problem with this series is it breaks an old kernel with new dt. You
> > > can partially mitigate that with stable kernel backport, but IMO keeping
> > > the old name is not a burden to maintain.
> >
> > As suggested I only removed vpll from the binding document, but not from
> > the code. The code still handles the old binding as well.
> 
> The problem is updating rk3399.dtsi. That change won't work with old
> kernels because they won't look for 'ref'. Since you shouldn't change
> it, the binding needs to cover both the old and new cases.

is "newer dt with old kernel" really a case these days?

I do understand the new kernel old dt case - for example with the
dtb being provided by firmware.

But which user would get the idea of updating only the devicetree
while staying with an older kernel?