phy: zynqmp: Add debugfs support

Add support for printing some basic status information to debugfs. This
is helpful when debugging phy consumers to make sure they are configuring
the phy appropriately.

Signed-off-by: Sean Anderson <sean.anderson@linux.dev>
Link: https://lore.kernel.org/r/20240628205540.3098010-6-sean.anderson@linux.dev
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Author: Sean Anderson

drivers/phy/xilinx/phy-zynqmp.c

@@ -13,6 +13,7 @@
  */
 
 #include <linux/clk.h>
+#include <linux/debugfs.h>
 #include <linux/delay.h>
 #include <linux/io.h>
 #include <linux/kernel.h>
@@ -123,6 +124,15 @@
 #define ICM_PROTOCOL_DP			0x4
 #define ICM_PROTOCOL_SGMII		0x5
 
+static const char *const xpsgtr_icm_str[] = {
+	[ICM_PROTOCOL_PD] = "none",
+	[ICM_PROTOCOL_PCIE] = "PCIe",
+	[ICM_PROTOCOL_SATA] = "SATA",
+	[ICM_PROTOCOL_USB] = "USB",
+	[ICM_PROTOCOL_DP] = "DisplayPort",
+	[ICM_PROTOCOL_SGMII] = "SGMII",
+};
+
 /* Test Mode common reset control  parameters */
 #define TM_CMN_RST			0x10018
 #define TM_CMN_RST_EN			0x1
@@ -787,6 +797,34 @@ static struct phy *xpsgtr_xlate(struct device *dev,
 	return ERR_PTR(-EINVAL);
 }
 
+/*
+ * DebugFS
+ */
+
+static int xpsgtr_status_read(struct seq_file *seq, void *data)
+{
+	struct device *dev = seq->private;
+	struct xpsgtr_phy *gtr_phy = dev_get_drvdata(dev);
+	struct clk *clk;
+	u32 pll_status;
+
+	mutex_lock(&gtr_phy->phy->mutex);
+	pll_status = xpsgtr_read_phy(gtr_phy, L0_PLL_STATUS_READ_1);
+	clk = gtr_phy->dev->clk[gtr_phy->refclk];
+
+	seq_printf(seq, "Lane:            %u\n", gtr_phy->lane);
+	seq_printf(seq, "Protocol:        %s\n",
+		   xpsgtr_icm_str[gtr_phy->protocol]);
+	seq_printf(seq, "Instance:        %u\n", gtr_phy->instance);
+	seq_printf(seq, "Reference clock: %u (%pC)\n", gtr_phy->refclk, clk);
+	seq_printf(seq, "Reference rate:  %lu\n", clk_get_rate(clk));
+	seq_printf(seq, "PLL locked:      %s\n",
+		   pll_status & PLL_STATUS_LOCKED ? "yes" : "no");
+
+	mutex_unlock(&gtr_phy->phy->mutex);
+	return 0;
+}
+
 /*
  * Power Management
  */
@@ -936,6 +974,8 @@ static int xpsgtr_probe(struct platform_device *pdev)
 
 		gtr_phy->phy = phy;
 		phy_set_drvdata(phy, gtr_phy);
+		debugfs_create_devm_seqfile(&phy->dev, "status", phy->debugfs,
+					    xpsgtr_status_read);
 	}
 
 	/* Register the PHY provider. */