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

From: Abel Vesa <abel.vesa@linaro.org>
To: Konrad Dybcio <konrad.dybcio@linaro.org>
Cc: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
	Vinod Koul <vkoul@kernel.org>,
	Kishon Vijay Abraham I <kishon@kernel.org>,
	Bjorn Andersson <andersson@kernel.org>,
	Rob Herring <robh+dt@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Conor Dooley <conor+dt@kernel.org>,
	Johan Hovold <johan@kernel.org>,
	linux-phy@lists.infradead.org, linux-kernel@vger.kernel.org,
	linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org
Subject: Re: [PATCH 0/3] phy: qcom: edp: Add support for DT phy mode configuration
Date: Mon, 15 Jan 2024 11:52:09 +0200	[thread overview]
Message-ID: <ZaUASV+0gc/Bufmw@linaro.org> (raw)
In-Reply-To: <6179e3c7-f399-4b0f-abb0-aaf5e549d8d9@linaro.org>

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@linaro.org> 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@linaro.org/
> >>
> >> 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.

> 
> Konrad

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