linux-kernel - Re: [PATCH v2 2/2] arm64: dts: qcom: sa8775p: Remove max link speed property for PCIe EP

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Message-ID: <CAMyL0qNQWN1ORReZu3wrw_Ex+nAmAJxhTMCt4Jw6PyEN4tEtGQ@mail.gmail.com>
Date: Mon, 19 May 2025 17:46:04 +0530
From: Mrinmay Sarkar <mrinmay.sarkar@....qualcomm.com>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Cc: Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Vinod Koul <vkoul@...nel.org>,
        Kishon Vijay Abraham I <kishon@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-phy@...ts.infradead.org,
        devicetree@...r.kernel.org, krishna.chundru@....qualcomm.com,
        quic_vbadigan@...cinc.com, quic_nayiluri@...cinc.com,
        quic_ramkri@...cinc.com, quic_nitegupt@...cinc.com,
        Mrinmay Sarkar <quic_msarkar@...cinc.com>
Subject: Re: [PATCH v2 2/2] arm64: dts: qcom: sa8775p: Remove max link speed
 property for PCIe EP

On Sat, May 17, 2025 at 3:33 AM Dmitry Baryshkov
<dmitry.baryshkov@....qualcomm.com> wrote:
>
> On Fri, May 16, 2025 at 03:59:02PM +0530, Mrinmay Sarkar wrote:
> > On Fri, May 16, 2025 at 2:30 PM Konrad Dybcio
> > <konrad.dybcio@....qualcomm.com> wrote:
> > >
> > > On 5/14/25 6:38 PM, neil.armstrong@...aro.org wrote:
> > > > On 14/05/2025 13:37, Mrinmay Sarkar wrote:
> > > >> From: Mrinmay Sarkar <mrinmay.sarkar@....qualcomm.com>
> > > >>
> > > >> The maximum link speed was previously restricted to Gen3 due to the
> > > >> absence of Gen4 equalization support in the driver.
> > > >>
> > > >> Add change to remove max link speed property, Since Gen4 equalization
> > > >> support has already been added into the driver.
> > > >
> > > > Which driver, PHY or Controller ?
> > >
> > > Controller, see
> > >
> > > 09483959e34d ("PCI: dwc: Add support for configuring lane equalization presets")
> >
> > Yes, this patch is helping to solve gen4 stability issue.
> > >
> > > and commits around it
> > >
> > > does this change depends on the patch 1 PHY settings update ?
> > >
> > > That I'm curious about too, but I would guesstimate no
> > >
> > this change doesn't depends on the patch 1 PHY settings update
>
> Then what has changed, as previously it was documented to have stability
> issues.
>
Actually this controller change is solving the stability issue with
gen4: "PCI: qcom: Add equalization settings for 16.0 GT/s"
https://lore.kernel.org/linux-pci/20240911-pci-qcom-gen4-stability-v7-3-743f5c1fd027@linaro.org/

Thanks,
Mrinmay
> --
> With best wishes
> Dmitry