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

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Date:   Tue, 14 Mar 2023 16:25:29 +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 3/14/2023 4:06 PM, Sricharan Ramabadhran wrote:
> 
> 
> 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 ?

  Also, since its 1 bit, all are status and not count.
  Not sure, if you want it to limit this debug based on 'mhi' property
  being populated ?

Regards,
  Sricharan