linux-kernel - Re: [PATCH v3 19/19] PCI: qcom: Expose link transition counts via debugfs for v2.4.0

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Message-ID: <e02980a9-34ca-9b9a-389a-01c599612140@quicinc.com>
Date:   Tue, 14 Mar 2023 16:06:07 +0530
From:   Sricharan Ramabadhran <quic_srichara@...cinc.com>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        <andersson@...nel.org>, <lpieralisi@...nel.org>, <kw@...ux.com>,
        <krzysztof.kozlowski+dt@...aro.org>, <robh@...nel.org>
CC:     <konrad.dybcio@...aro.org>, <linux-arm-msm@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-pci@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 19/19] PCI: qcom: Expose link transition counts via
 debugfs for v2.4.0



On 3/10/2023 9:38 AM, Manivannan Sadhasivam wrote:
> Qualcomm PCIe controllers of version v2.4.0 have debug registers in the
> PARF region that count PCIe link transitions. Expose them over debugfs to
> userspace to help debug the low power issues.
> 
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> ---
>   drivers/pci/controller/dwc/pcie-qcom.c | 33 ++++++++++++++++++++++++++
>   1 file changed, 33 insertions(+)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> index f99b7e7f3f73..0b41f007fa90 100644
> --- a/drivers/pci/controller/dwc/pcie-qcom.c
> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> @@ -37,6 +37,7 @@
>   /* PARF registers */
>   #define PARF_SYS_CTRL				0x00
>   #define PARF_PM_CTRL				0x20
> +#define PARF_PM_STTS				0x24
>   #define PARF_PCS_DEEMPH				0x34
>   #define PARF_PCS_SWING				0x38
>   #define PARF_PHY_CTRL				0x40
> @@ -84,6 +85,12 @@
>   /* PARF_PM_CTRL register fields */
>   #define REQ_NOT_ENTR_L1				BIT(5)
>   
> +/* PARF_PM_STTS register fields */
> +#define PM_LINKST_IN_L1SUB			BIT(8)
> +#define PM_LINKST_IN_L0S			BIT(7)
> +#define PM_LINKST_IN_L2				BIT(5)
> +#define PM_LINKST_IN_L1				BIT(4)
> +
>   /* PARF_PCS_DEEMPH register fields */
>   #define PCS_DEEMPH_TX_DEEMPH_GEN1(x)		FIELD_PREP(GENMASK(21, 16), x)
>   #define PCS_DEEMPH_TX_DEEMPH_GEN2_3_5DB(x)	FIELD_PREP(GENMASK(13, 8), x)
> @@ -737,6 +744,31 @@ static int qcom_pcie_post_init_2_4_0(struct qcom_pcie *pcie)
>   	return 0;
>   }
>   
> +static int qcom_pcie_debugfs_func_2_4_0(struct seq_file *s, void *data)
> +{
> +	struct qcom_pcie *pcie = (struct qcom_pcie *) dev_get_drvdata(s->private);
> +
> +	seq_printf(s, "L0s transition count: %u\n",
> +		   readl_relaxed(pcie->parf + PM_LINKST_IN_L0S));
> +
> +	seq_printf(s, "L1 transition count: %u\n",
> +		   readl_relaxed(pcie->parf + PM_LINKST_IN_L1));
> +
> +	seq_printf(s, "L1.1 transition count: %u\n",
> +		   readl_relaxed(pcie->parf + PM_LINKST_IN_L1SUB));
> +
> +	seq_printf(s, "L2 transition count: %u\n",
> +		   readl_relaxed(pcie->parf + PM_LINKST_IN_L2));
> +

  Using bitmask as register offset ? instead use PM_STTS and bitmask it ?

Regards,
  Sricharan