Re: [PATCH v2 17/17] PCI: qcom: Expose link transition counts via debugfs

[Manivannan Sadhasivam]

On Thu, Mar 09, 2023 at 05:21:38PM +0530, Sricharan Ramabadhran wrote:
> 
> 
> On 3/9/2023 2:21 PM, Manivannan Sadhasivam wrote:
> > Qualcomm PCIe controllers have debug registers in the MHI region that
> > count PCIe link transitions. Expose them over debugfs to userspace to
> > help debug the low power issues.
> > 
> > Note that even though the registers are prefixed as PARF_, they don't
> > live under the "parf" register region. The register naming is following
> > the Qualcomm's internal documentation as like other registers.
> > 
> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>
> > ---
> >   drivers/pci/controller/dwc/pcie-qcom.c | 59 ++++++++++++++++++++++++++
> >   1 file changed, 59 insertions(+)
> > 
> > diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> > index e1180c84f0fa..6d9bde64c9e9 100644
> > --- a/drivers/pci/controller/dwc/pcie-qcom.c
> > +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> > @@ -10,6 +10,7 @@
> >   #include <linux/clk.h>
> >   #include <linux/crc8.h>
> > +#include <linux/debugfs.h>
> >   #include <linux/delay.h>
> >   #include <linux/gpio/consumer.h>
> >   #include <linux/interconnect.h>
> > @@ -62,6 +63,13 @@
> >   #define AXI_MSTR_RESP_COMP_CTRL1		0x81c
> >   #define MISC_CONTROL_1_REG			0x8bc
> > +/* MHI registers */
> > +#define PARF_DEBUG_CNT_PM_LINKST_IN_L2		0xc04
> > +#define PARF_DEBUG_CNT_PM_LINKST_IN_L1		0xc0c
> > +#define PARF_DEBUG_CNT_PM_LINKST_IN_L0S		0xc10
> > +#define PARF_DEBUG_CNT_AUX_CLK_IN_L1SUB_L1	0xc84
> > +#define PARF_DEBUG_CNT_AUX_CLK_IN_L1SUB_L2	0xc88
> > +
> >   /* PARF_SYS_CTRL register fields */
> >   #define MAC_PHY_POWERDOWN_IN_P2_D_MUX_EN	BIT(29)
> >   #define MST_WAKEUP_EN				BIT(13)
> > @@ -229,11 +237,13 @@ struct qcom_pcie {
> >   	struct dw_pcie *pci;
> >   	void __iomem *parf;			/* DT parf */
> >   	void __iomem *elbi;			/* DT elbi */
> > +	void __iomem *mhi;
> >   	union qcom_pcie_resources res;
> >   	struct phy *phy;
> >   	struct gpio_desc *reset;
> >   	struct icc_path *icc_mem;
> >   	const struct qcom_pcie_cfg *cfg;
> > +	struct dentry *debugfs;
> >   };
> >   #define to_qcom_pcie(x)		dev_get_drvdata((x)->dev)
> > @@ -1385,6 +1395,37 @@ static void qcom_pcie_icc_update(struct qcom_pcie *pcie)
> >   	}
> >   }
> > +static int qcom_pcie_link_transition_count(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->mhi + PARF_DEBUG_CNT_PM_LINKST_IN_L0S));
> > +
> > +	seq_printf(s, "L1 transition count: %u\n",
> > +		   readl_relaxed(pcie->mhi + PARF_DEBUG_CNT_PM_LINKST_IN_L1));
> > +
> > +	seq_printf(s, "L1.1 transition count: %u\n",
> > +		   readl_relaxed(pcie->mhi + PARF_DEBUG_CNT_AUX_CLK_IN_L1SUB_L1));
> > +
> > +	seq_printf(s, "L1.2 transition count: %u\n",
> > +		   readl_relaxed(pcie->mhi + PARF_DEBUG_CNT_AUX_CLK_IN_L1SUB_L2));
> > +
> > +	seq_printf(s, "L2 transition count: %u\n",
> > +		   readl_relaxed(pcie->mhi + PARF_DEBUG_CNT_PM_LINKST_IN_L2));
> > +
> > +	return 0;
> > +}
> > +
> > +static void qcom_pcie_init_debugfs(struct qcom_pcie *pcie)
> > +{
> > +	struct dw_pcie *pci = pcie->pci;
> > +
> > +	debugfs_create_devm_seqfile(pci->dev, "link_transition_count", pcie->debugfs,
> > +				    qcom_pcie_link_transition_count);
> > +}
> > +
> >   static int qcom_pcie_probe(struct platform_device *pdev)
> >   {
> >   	struct device *dev = &pdev->dev;
> > @@ -1392,6 +1433,7 @@ static int qcom_pcie_probe(struct platform_device *pdev)
> >   	struct dw_pcie *pci;
> >   	struct qcom_pcie *pcie;
> >   	const struct qcom_pcie_cfg *pcie_cfg;
> > +	char *name;
> >   	int ret;
> >   	pcie_cfg = of_device_get_match_data(dev);
> > @@ -1439,6 +1481,12 @@ static int qcom_pcie_probe(struct platform_device *pdev)
> >   		goto err_pm_runtime_put;
> >   	}
> > +	pcie->mhi = devm_platform_ioremap_resource_byname(pdev, "mhi");
> > +	if (IS_ERR(pcie->mhi)) {
> > +		ret = PTR_ERR(pcie->mhi);
> > +		goto err_pm_runtime_put;
> > +	}
> > +
> 
>  Tested this series on ipq4019-ap.dk07.1-c1 board and the above hunk
>  breaks enumeration because there is no 'mhi' region. All the debug bits
>  used in the transition_count function is inside the PARF_STTS register
>  at offset 0x24 inside the PARF region.
> 

Ah, "mhi" is supposed to be optional, my bad. Will fix it in next revision.

>  Register: PCIE_0_PCIE20_PARF_PM_STTS | 0x80024
>  Offset:    0x24    Reset State:    0x00040000
> 

Hmm, is this register present on other IPQ/APQ SoCs?

> Bits    Field Name
> 31    LINK_REQ_RST_NOT
> 30    XMLH_LINK_UP
> 29    PM_DSTATE_0
> 0x0: D0
> 0x1: D3
> 28    PHYSTATUS
> 27:16    PM_DSTATE
> 15:12    PM_PME_EN
> 11    PHYCLK_REQ_N
> 10    L1SS_CLKREQN_OE
> 9    L1SS_CLKREQN_IN
> 8    PM_LINKST_IN_L1SUB
> 7    PM_LINKST_IN_L0S
> 6    PM_LINKST_L2_EXIT
> 5    PM_LINKST_IN_L2
> 4    PM_LINKST_IN_L1
> 3:0    PM_STATUS
> 
> Otherwise, with rest of the patches enumeration was fine.
> Tested with a pcie ethernet adapter.
> 

Thanks a lot for testing!

- Mani

> Regards,
>  Sricharan

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