PCI: qcom-ep: Expose link transition counts via debugfs

Qualcomm PCIe controllers have debug registers in the MMIO region
that count PCIe link transitions. Expose them over debugfs to
userspace to help debug the low power issues.

Link: https://lore.kernel.org/r/20220914075350.7992-6-manivannan.sadhasivam@linaro.orgSigned-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>

drivers/pci/controller/dwc/pcie-qcom-ep.c

@@ -10,6 +10,7 @@
  */
 
 #include <linux/clk.h>
+#include <linux/debugfs.h>
 #include <linux/delay.h>
 #include <linux/gpio/consumer.h>
 #include <linux/mfd/syscon.h>
@@ -45,6 +46,11 @@
 #define PARF_ATU_BASE_ADDR			0x634
 #define PARF_ATU_BASE_ADDR_HI			0x638
 #define PARF_SRIS_MODE				0x644
+#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
 #define PARF_DEVICE_TYPE			0x1000
 #define PARF_BDF_TO_SID_CFG			0x2c00
 
@@ -135,12 +141,14 @@ enum qcom_pcie_ep_link_status {
  * @pci: Designware PCIe controller struct
  * @parf: Qualcomm PCIe specific PARF register base
  * @elbi: Designware PCIe specific ELBI register base
+ * @mmio: MMIO register base
  * @perst_map: PERST regmap
  * @mmio_res: MMIO region resource
  * @core_reset: PCIe Endpoint core reset
  * @reset: PERST# GPIO
  * @wake: WAKE# GPIO
  * @phy: PHY controller block
+ * @debugfs: PCIe Endpoint Debugfs directory
  * @clks: PCIe clocks
  * @num_clks: PCIe clocks count
  * @perst_en: Flag for PERST enable
@@ -154,6 +162,7 @@ struct qcom_pcie_ep {
 
 	void __iomem *parf;
 	void __iomem *elbi;
+	void __iomem *mmio;
 	struct regmap *perst_map;
 	struct resource *mmio_res;
 
@@ -161,6 +170,7 @@ struct qcom_pcie_ep {
 	struct gpio_desc *reset;
 	struct gpio_desc *wake;
 	struct phy *phy;
+	struct dentry *debugfs;
 
 	struct clk_bulk_data *clks;
 	int num_clks;
@@ -446,6 +456,9 @@ static int qcom_pcie_ep_get_io_resources(struct platform_device *pdev,
 
 	pcie_ep->mmio_res = platform_get_resource_byname(pdev, IORESOURCE_MEM,
 							 "mmio");
+	pcie_ep->mmio = devm_pci_remap_cfg_resource(dev, pcie_ep->mmio_res);
+	if (IS_ERR(pcie_ep->mmio))
+		return PTR_ERR(pcie_ep->mmio);
 
 	syscon = of_parse_phandle(dev->of_node, "qcom,perst-regs", 0);
 	if (!syscon) {
@@ -627,6 +640,37 @@ static int qcom_pcie_ep_raise_irq(struct dw_pcie_ep *ep, u8 func_no,
 	}
 }
 
+static int qcom_pcie_ep_link_transition_count(struct seq_file *s, void *data)
+{
+	struct qcom_pcie_ep *pcie_ep = (struct qcom_pcie_ep *)
+				     dev_get_drvdata(s->private);
+
+	seq_printf(s, "L0s transition count: %u\n",
+		   readl_relaxed(pcie_ep->mmio + PARF_DEBUG_CNT_PM_LINKST_IN_L0S));
+
+	seq_printf(s, "L1 transition count: %u\n",
+		   readl_relaxed(pcie_ep->mmio + PARF_DEBUG_CNT_PM_LINKST_IN_L1));
+
+	seq_printf(s, "L1.1 transition count: %u\n",
+		   readl_relaxed(pcie_ep->mmio + PARF_DEBUG_CNT_AUX_CLK_IN_L1SUB_L1));
+
+	seq_printf(s, "L1.2 transition count: %u\n",
+		   readl_relaxed(pcie_ep->mmio + PARF_DEBUG_CNT_AUX_CLK_IN_L1SUB_L2));
+
+	seq_printf(s, "L2 transition count: %u\n",
+		   readl_relaxed(pcie_ep->mmio + PARF_DEBUG_CNT_PM_LINKST_IN_L2));
+
+	return 0;
+}
+
+static void qcom_pcie_ep_init_debugfs(struct qcom_pcie_ep *pcie_ep)
+{
+	struct dw_pcie *pci = &pcie_ep->pci;
+
+	debugfs_create_devm_seqfile(pci->dev, "link_transition_count", pcie_ep->debugfs,
+				    qcom_pcie_ep_link_transition_count);
+}
+
 static const struct pci_epc_features qcom_pcie_epc_features = {
 	.linkup_notifier = true,
 	.core_init_notifier = true,
@@ -659,6 +703,7 @@ static int qcom_pcie_ep_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
 	struct qcom_pcie_ep *pcie_ep;
+	char *name;
 	int ret;
 
 	pcie_ep = devm_kzalloc(dev, sizeof(*pcie_ep), GFP_KERNEL);
@@ -690,8 +735,21 @@ static int qcom_pcie_ep_probe(struct platform_device *pdev)
 	if (ret)
 		goto err_disable_resources;
 
+	name = devm_kasprintf(dev, GFP_KERNEL, "%pOFP", dev->of_node);
+	if (!name) {
+		ret = -ENOMEM;
+		goto err_disable_irqs;
+	}
+
+	pcie_ep->debugfs = debugfs_create_dir(name, NULL);
+	qcom_pcie_ep_init_debugfs(pcie_ep);
+
 	return 0;
 
+err_disable_irqs:
+	disable_irq(pcie_ep->global_irq);
+	disable_irq(pcie_ep->perst_irq);
+
 err_disable_resources:
 	qcom_pcie_disable_resources(pcie_ep);
 
@@ -705,6 +763,8 @@ static int qcom_pcie_ep_remove(struct platform_device *pdev)
 	disable_irq(pcie_ep->global_irq);
 	disable_irq(pcie_ep->perst_irq);
 
+	debugfs_remove_recursive(pcie_ep->debugfs);
+
 	if (pcie_ep->link_status == QCOM_PCIE_EP_LINK_DISABLED)
 		return 0;