linux-kernel - Re: [RFC 08/10] PCI: qcom: Add support for disabling ASPM L0s in devicetree

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Date: Mon, 12 Feb 2024 13:34:49 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Johan Hovold <johan+linaro@...nel.org>
Cc: Bjorn Andersson <andersson@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Konrad Dybcio <konrad.dybcio@...aro.org>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	linux-arm-msm@...r.kernel.org, linux-pci@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC 08/10] PCI: qcom: Add support for disabling ASPM L0s in
 devicetree

On Mon, Feb 12, 2024 at 05:50:41PM +0100, Johan Hovold wrote:
> A recent commit started enabling ASPM unconditionally when the hardware
> claims to support it. This triggers Correctable Errors for some PCIe
> devices on machines like the Lenovo ThinkPad X13s, which could indicate
> an incomplete driver ASPM implementation or that the hardware does in
> fact not support L0s.

I think it would be useful for debugging purposes to identify the
specific commit.  Maybe it's 9f4f3dfad8cf ("PCI: qcom: Enable ASPM for
platforms supporting 1.9.0 ops") ?

> Add support for disabling ASPM L0s in the devicetree when it is not
> supported on a particular machine and controller.
> 
> Note that only the 1.9.0 ops enable ASPM currently.
> 
> Fixes: a9a023c05697 ("PCI: qcom: Add support for disabling ASPM L0s in devicetree")

I don't see this SHA1 in the PCI tree; is it a stable SHA1 from
somewhere else?

> Signed-off-by: Johan Hovold <johan+linaro@...nel.org>
> ---
>  drivers/pci/controller/dwc/pcie-qcom.c | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> index 2455decc574a..071741b81644 100644
> --- a/drivers/pci/controller/dwc/pcie-qcom.c
> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> @@ -273,6 +273,25 @@ static int qcom_pcie_start_link(struct dw_pcie *pci)
>  	return 0;
>  }
>  
> +static void qcom_pcie_clear_aspm_l0s(struct dw_pcie *pci)
> +{
> +	u16 offset;
> +	u32 val;
> +
> +	if (!of_property_read_bool(pci->dev->of_node, "aspm-no-l0s"))
> +		return;
> +
> +	offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
> +
> +	dw_pcie_dbi_ro_wr_en(pci);
> +
> +	val = readl(pci->dbi_base + offset + PCI_EXP_LNKCAP);
> +	val &= ~PCI_EXP_LNKCAP_ASPM_L0S;
> +	writel(val, pci->dbi_base + offset + PCI_EXP_LNKCAP);
> +
> +	dw_pcie_dbi_ro_wr_dis(pci);
> +}
> +
>  static void qcom_pcie_clear_hpc(struct dw_pcie *pci)
>  {
>  	u16 offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
> @@ -962,6 +981,7 @@ static int qcom_pcie_init_2_7_0(struct qcom_pcie *pcie)
>  
>  static int qcom_pcie_post_init_2_7_0(struct qcom_pcie *pcie)
>  {
> +	qcom_pcie_clear_aspm_l0s(pcie->pci);
>  	qcom_pcie_clear_hpc(pcie->pci);
>  
>  	return 0;
> -- 
> 2.43.0
>