linux-kernel - Re: [PATCH v2 8/9] arm64: dts: qcom: ipq8074: fix Gen3 PCIe node

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Message-ID: <20230228132043.GC4839@thinkpad>
Date:   Tue, 28 Feb 2023 18:50:43 +0530
From:   Manivannan Sadhasivam <mani@...nel.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Robert Marko <robimarko@...il.com>, Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>, bhelgaas@...gle.com,
        lpieralisi@...nel.org, Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        krzysztof.kozlowski+dt@...aro.org,
        Manivannan Sadhasivam <mani@...nel.org>, 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, Abel Vesa <abelvesa@...nel.org>,
        Jingoo Han <jingoohan1@...il.com>,
        Gustavo Pimentel <gustavo.pimentel@...opsys.com>
Subject: Re: [PATCH v2 8/9] arm64: dts: qcom: ipq8074: fix Gen3 PCIe node

On Thu, Feb 02, 2023 at 10:42:15AM +0100, Arnd Bergmann wrote:
> On Thu, Feb 2, 2023, at 10:16, Robert Marko wrote:
> > On Mon, 30 Jan 2023 at 18:11, Arnd Bergmann <arnd@...db.de> wrote:
> >> On Fri, Jan 13, 2023, at 17:44, Robert Marko wrote:
> >
> > As pointed out in the commit description, the ranges property was copied
> > from the QCA-s downstream 5.4 kernel [1] as I dont have any documentation
> > on the SoC.
> >
> > I have runtime tested this on Xiaomi AX3600 which has a QCA9889 card on the
> > Gen3 PCIe port, and on Xiaomi AX9000 which has QCA9889 on Gen2 port
> > and QCN9074 on the Gen3 port and they are working fine.
> 
> Neither of those use I/O ports though, nor does any other sensible
> device that was made in the past decade.
> 
> The compatible string tells me that this is a designware pcie block,
> so I think driver actually sets up the mapping based on the ranges
> property in DT in dw_pcie_iatu_detect() and dw_pcie_iatu_setup(),
> rather than the mapping being determined by hardware or firmware
> in advance.
> 
> Not sure about the general policy we have for this case, maybe the
> pci controller or pci-dwc maintainers have an idea here. I would
> think it's better to either have no I/O ranges in DT or have
> sensible ones than ones that are clearly bogus, if the controller
> is able to set up the ranges.
> 

Just happen to see this thread and I agree that the I/O port range is indeeed
bogus. This is due to the fact that no one tested I/O range with a compatible
device.

I'm not sure about the PCI policy though but we should fix the mapping across
all SoCs. I will send out a series for that.

Thanks for spotting, Arnd!

- Mani

>      Arnd

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