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: <1527272e-fe7a-435d-a279-3ff73c245200@linaro.org>
Date: Tue, 20 May 2025 09:25:51 +0200
From: Neil Armstrong <neil.armstrong@...aro.org>
To: Mrinmay Sarkar <mrinmay.sarkar@....qualcomm.com>,
 Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Cc: Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
 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 19/05/2025 14:16, Mrinmay Sarkar wrote:
> 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/

Ok so those patches should be send separately and will reduce maintainers work
by trying to figure out if there's a dependency.

Neil

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