[PATCH 2/3] drm/msm/dsi: Use "ref" fw clock instead of global name for VCO parent

[Dmitry Baryshkov]

On Mon, 30 Aug 2021 at 00:53, Marijn Suijten
<marijn.suijten at somainline.org> wrote:
>
> Hi Dmitry,
>
> On 8/29/21 10:39 PM, Dmitry Baryshkov wrote:
> > Hi,
> >
> > On Sun, 29 Aug 2021 at 23:30, Marijn Suijten
> > <marijn.suijten at somainline.org> wrote:
> >>
> >> All DSI PHY/PLL drivers were referencing their VCO parent clock by a
> >> global name, most of which don't exist or have been renamed.  These
> >> clock drivers seem to function fine without that except the 14nm driver
> >> for the sdm6xx [1].
> >>
> >> At the same time all DTs provide a "ref" clock as per the requirements
> >> of dsi-phy-common.yaml, but the clock is never used.  This patchset puts
> >> that clock to use without relying on a global clock name, so that all
> >> dependencies are explicitly defined in DT (the firmware) in the end.
> >
> > msm8974 (28nm-hpm) does not define the "ref" clock. So you'd have to:
> > 1) add ref clock to the dtsi (should come in a separate patch).
>
>
> Thanks for double-checking and noticing this!  I've queued up this patch
> for v2.
>
> > 2) add .name = "xo" as a fallback to the 28nm driver (to be compatible
> > with older devices)
>
>
> Are there msm8974 devices out there that might upgrade kernels, but not
> firmware (DT)?  On other boards (sdm630) I'm removing these from various
> drivers as to not have any possibility of relying on global names, in
> favour of having the clock dependencies fully specified in the DT.

IIUC it is a general policy of trying to be (somewhat)
backwards-compatible. For example because your dts might come from a
different source/be a part of different build process/etc.

>
> > Other than that this looks good to me.
>
>
> Any r-b/a-b/t-b I can pick up for the next round?

Let's get those issues fixed and I'll respond with R-B tags


-- 
With best wishes
Dmitry