Re: [PATCH] arm64: dts: qcom: sc8280xp-x13s: Use the correct DP PHY compatible

[Konrad Dybcio]

On 10/17/23 05:28, Bjorn Andersson wrote:
> On Mon, Oct 16, 2023 at 12:10:18PM +0300, Dmitry Baryshkov wrote:
> > On Mon, 16 Oct 2023 at 12:01, Johan Hovold <johan@xxxxxxxxxx> wrote:
> > > On Mon, Oct 16, 2023 at 11:51:33AM +0300, Dmitry Baryshkov wrote:
> > > > On Fri, 29 Sept 2023 at 19:03, Konrad Dybcio <konrad.dybcio@xxxxxxxxxx> wrote:
> > > > > The DP PHY needs different settings when an eDP display is used.
> > > > > Make sure these apply on the X13s.
> > > >
> > > > Could you please clarify, is it the same PHY type, just being
> > > > repurposed for eDP or is it a different PHY type?
> > >
> > > Same PHY, just different settings AFAIK.
> > >
> > > > If the former is the case (and the same PHY can be used for both DP
> > > > and eDP), it should carry the same compatible string and use software
> > > > mechanisms (e.g. phy_set_mode_ext()) to be programmed for the correct
> > > > operation mode.
> > >
> > > Possibly, but that's not how the current binding and implementation
> > > works:
> > >
> > >          6993c079cd58 ("dt-bindings: phy: qcom-edp: Add SC8280XP PHY compatibles")
> > >          2300d1cb24b3 ("phy: qcom: edp: Introduce support for DisplayPort")
> > >          3b7267dec445 ("phy: qcom: edp: Add SC8280XP eDP and DP PHYs")
> > >
> > >          https://lore.kernel.org/lkml/20220810040745.3582985-1-bjorn.andersson@xxxxxxxxxx/
> > >
> > > And you'd still need to infer the mode from DT somehow.
> >
> > If it is the same hardware block, it seems incorrect to have two
> > different compat entries. For example, for PCIe RC vs PCIe EP we
> > specify the PHY mode from the host controller driver.
> > I'd say, we need to fix the bindings for both DP/eDP controller and
> > the PHY.  See the `phy-mode` DT property for example.
>
> It is one hardware block, supporting both eDP and DP, so I like your
> suggestion of having a single compatible instead and using some other
> means of defining the configuration. I just wasn't able to find a
> better way to do so back when I wrote the binding/driver...
Since this one is still unused, we can deprecate it (not sure if remove, 
but deprecate) and add phy-type instead. I was quite surprised to see 
that a new compatible was added as well :/

Konrad