Re: [PATCH 0/3] phy: qcom: edp: Add support for DT phy mode configuration

[Konrad Dybcio]

On 1/15/24 10:52, Abel Vesa wrote:
> On 24-01-03 14:42:49, Konrad Dybcio wrote:
> > On 21.12.2023 17:27, Dmitry Baryshkov wrote:
> > > On Tue, 19 Dec 2023 at 22:55, Abel Vesa <abel.vesa@xxxxxxxxxx> wrote:
> > > > Until now, all platform that supported both eDP and DP had different
> > > > compatibles for each mode. Using different compatibles for basically
> > > > the same IP block but for a different configuration is bad way all
> > > > around. There is a new compute platform from Qualcomm that supports
> > > > both eDP and DP with the same PHY. So instead of following the old
> > > > method, we should allow the mode to be configured from devicetree.
> > > >
> > > > There has been an off-list discussion on what would be the right way
> > > > to pass on the PHY mode information to the driver and it has been
> > > > concluded that phy-cells is the way to go. This means that basically
> > > > the controller will pass another value (that is, the PHY type) to
> > > > its 'phys' DT property.
> > > >
> > > > For this, we need both the bindings value and the PHY mode value to be
> > > > added as well.
> > > >
> > > > The controller part will follow shortly. But for now, lets see where
> > > > this is going.
> > > >
> > > > There has been another attempt at this here:
> > > > https://lore.kernel.org/all/20231122-phy-qualcomm-edp-x1e80100-v3-3-576fc4e9559d@xxxxxxxxxx/
> > > >
> > > > Compared to that version, this one uses the phy-cells method and drops
> > > > the X1E80100 support. The X1E80100 support will be a separate patchset.
> > >
> > > After several back and forth discussions, I think that this approach
> > > is not correct and not that easy to extend. Instead I'd like to
> > > suggest adding a property to the DP controller, which enables eDP
> > > behaviour (and thus makes DP driver call phy_set_mode()). Something
> > > like this:
> > > dp: displayport-controller@ae0000 {
> > >      compatible = "qcom,sm8000-dp";
> > >      /* reg, interrupts, etc */
> > >     edp-interface;
> > >     /* or simpler */
> > >     is-edp;
> > > };
> > >
> > > What do you think?
> >
> > Please excuse my alzheimer, but why did we not go with phy-type after
> > the last discussion?
>
> phy-type would be a property of the phy. That way we would need pass
> the mode to the controller. So it was concluded that passing that
> information from the controller via phy_set_mode is more straightforward.

Eeh, reluctantly, I'm gonna say yes. It's not the prettiest solution,
but none of the ones I can think of seem much better.

Konrad