Re: [PATCH v4 3/5] PCI: qcom: Disable ASPM L0s for sc8280xp, sa8540p and sa8295p

[Manivannan Sadhasivam]

On Wed, Mar 06, 2024 at 10:56:49AM +0100, Johan Hovold wrote:
> Commit 9f4f3dfad8cf ("PCI: qcom: Enable ASPM for platforms supporting
> 1.9.0 ops") 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 when L0s is enabled,
> which could indicate an incomplete driver ASPM implementation or that
> the hardware does in fact not support L0s.
> 
> This has now been confirmed by Qualcomm to be the case for sc8280xp and
> its derivate platforms (e.g. sa8540p and sa8295p). Specifically, the PHY
> configuration used on these platforms is not correctly tuned for L0s and
> there is currently no updated configuration available.
> 
> Add a new flag to the driver configuration data and use it to disable
> ASPM L0s on sc8280xp, sa8540p and sa8295p for now.
> 
> Note that only the 1.9.0 ops enable ASPM currently.
> 
> Fixes: 9f4f3dfad8cf ("PCI: qcom: Enable ASPM for platforms supporting 1.9.0 ops")
> Cc: stable@xxxxxxxxxxxxxxx      # 6.7
> Signed-off-by: Johan Hovold <johan+linaro@xxxxxxxxxx>

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>

- Mani

> ---
>  drivers/pci/controller/dwc/pcie-qcom.c | 31 ++++++++++++++++++++++++--
>  1 file changed, 29 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> index 2ce2a3bd932b..9f83a1611a20 100644
> --- a/drivers/pci/controller/dwc/pcie-qcom.c
> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> @@ -229,6 +229,7 @@ struct qcom_pcie_ops {
>  
>  struct qcom_pcie_cfg {
>  	const struct qcom_pcie_ops *ops;
> +	bool no_l0s;
>  };
>  
>  struct qcom_pcie {
> @@ -272,6 +273,26 @@ static int qcom_pcie_start_link(struct dw_pcie *pci)
>  	return 0;
>  }
>  
> +static void qcom_pcie_clear_aspm_l0s(struct dw_pcie *pci)
> +{
> +	struct qcom_pcie *pcie = to_qcom_pcie(pci);
> +	u16 offset;
> +	u32 val;
> +
> +	if (!pcie->cfg->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);
> @@ -961,6 +982,7 @@ 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;
> @@ -1358,6 +1380,11 @@ static const struct qcom_pcie_cfg cfg_2_9_0 = {
>  	.ops = &ops_2_9_0,
>  };
>  
> +static const struct qcom_pcie_cfg cfg_sc8280xp = {
> +	.ops = &ops_1_9_0,
> +	.no_l0s = true,
> +};
> +
>  static const struct dw_pcie_ops dw_pcie_ops = {
>  	.link_up = qcom_pcie_link_up,
>  	.start_link = qcom_pcie_start_link,
> @@ -1629,11 +1656,11 @@ static const struct of_device_id qcom_pcie_match[] = {
>  	{ .compatible = "qcom,pcie-ipq8074-gen3", .data = &cfg_2_9_0 },
>  	{ .compatible = "qcom,pcie-msm8996", .data = &cfg_2_3_2 },
>  	{ .compatible = "qcom,pcie-qcs404", .data = &cfg_2_4_0 },
> -	{ .compatible = "qcom,pcie-sa8540p", .data = &cfg_1_9_0 },
> +	{ .compatible = "qcom,pcie-sa8540p", .data = &cfg_sc8280xp },
>  	{ .compatible = "qcom,pcie-sa8775p", .data = &cfg_1_9_0},
>  	{ .compatible = "qcom,pcie-sc7280", .data = &cfg_1_9_0 },
>  	{ .compatible = "qcom,pcie-sc8180x", .data = &cfg_1_9_0 },
> -	{ .compatible = "qcom,pcie-sc8280xp", .data = &cfg_1_9_0 },
> +	{ .compatible = "qcom,pcie-sc8280xp", .data = &cfg_sc8280xp },
>  	{ .compatible = "qcom,pcie-sdm845", .data = &cfg_2_7_0 },
>  	{ .compatible = "qcom,pcie-sdx55", .data = &cfg_1_9_0 },
>  	{ .compatible = "qcom,pcie-sm8150", .data = &cfg_1_9_0 },
> -- 
> 2.43.0
> 

-- 
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