linux-kernel - Re: [PATCH 2/9] arm64: dts: qcom: ipq8074: fix Gen3 PCIe QMP PHY

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Message-ID: <20221229172944.6lg6mb53uqj2hps6@builder.lan>
Date:   Thu, 29 Dec 2022 11:29:44 -0600
From:   Bjorn Andersson <andersson@...nel.org>
To:     Robert Marko <robimarko@...il.com>
Cc:     agross@...nel.org, konrad.dybcio@...aro.org, bhelgaas@...gle.com,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        mani@...nel.org, lpieralisi@...nel.org, kw@...ux.com,
        svarbanov@...sol.com, shawn.guo@...aro.org,
        linux-arm-msm@...r.kernel.org, linux-pci@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/9] arm64: dts: qcom: ipq8074: fix Gen3 PCIe QMP PHY

On Wed, Dec 28, 2022 at 12:10:17PM +0100, Robert Marko wrote:
> On Tue, 27 Dec 2022 at 20:20, Bjorn Andersson <andersson@...nel.org> wrote:
> >
> > On Tue, Dec 06, 2022 at 10:51:40AM +0100, Robert Marko wrote:
> > > On Mon, 5 Dec 2022 at 22:52, Bjorn Andersson <andersson@...nel.org> wrote:
> > > >
> > > > On Wed, Nov 16, 2022 at 10:48:34PM +0100, Robert Marko wrote:
> > > > > IPQ8074 comes in 2 silicon versions:
> > > > > * v1 with 2x Gen2 PCIe ports and QMP PHY-s
> > > > > * v2 with 1x Gen3 and 1x Gen2 PCIe ports and QMP PHY-s
> > > > >
> > > > > v2 is the final and production version that is actually supported by the
> > > > > kernel, however it looks like PCIe related nodes were added for the v1 SoC.
> > > > >
> > > > > Now that we have Gen3 QMP PHY support, we can start fixing the PCIe support
> > > > > by fixing the Gen3 QMP PHY node first.
> > > > >
> > > > > Change the compatible to the Gen3 QMP PHY, correct the register space start
> > > > > and size, add the missing misc PCS register space.
> > > > >
> > > >
> > > > Does this imply that the current node doesn't actually work?
> > >
> > > Hi Bjorn,
> > > Yes, the node is for a completely different PHY generation, basically
> > > PCIe on IPQ8074
> > > is completely broken, hence this patch series.
> > >
> > > >
> > > > If that's the case, could we perhaps adopt Johan Hovolds' new binding
> > > > and drop the subnode in favor of just a flat reg covering the whole
> > > > QMP region?
> > >
> > > I have not seen that so far, any examples?
> > >
> >
> > See
> > Documentation/devicetree/bindings/phy/qcom,sc8280xp-qmp-pcie-phy.yaml in
> > v6.2-rc1.
> >
> > The idea is to, at least, use this for all new platforms introduced.
> >
> > And if the current definition doesn't actually work I suggest that we
> > replace it with the new one.
> 
> I understand the intention, but these bindings dont match the QMP generation
> found in IPQ8074 at all, and Gen3 has already been documented in bindings.
> 
> This would require updating the driver to carry the offsets and rework
> of bindings to
> not require power domains, etc for IPQ8074 as I have not found any
> code downstream
> to indicate it has GSDC-s for PCIe though I dont have any docs at all
> for the SoC.
> 

I was only thinking of the structural difference, not the power-domains
etc. But yes you're right that it means updating the driver and the
binding.

The end result would be much nicer though...

Regards,
Bjorn