PCI: dwc: Add debugfs property to provide LTSSM status of the PCIe link

Add the debugfs property to provide a view of the current link's LTSSM
status from the Root Port device.

Signed-off-by: Hans Zhang <18255117159@163.com>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Tested-by: Niklas Cassel <cassel@kernel.org>
Tested-by: Hrishikesh Deleep <hrishikesh.d@samsung.com>
Link: https://lore.kernel.org/r/20250223141848.231232-1-18255117159@163.com
[kwilczynski: commit log, refactor dw_ltssm_sts_string() to avoid
compilation errors on platforms that do not set CONFIG_PCIE_DW_HOST]
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>

2 files changed, 110 insertions, 0 deletions

diff --git a/drivers/pci/controller/dwc/pcie-designware-debugfs.c b/drivers/pci/controller/dwc/pcie-designware-debugfs.c
index 6100a0d1c709..9e6f4d00f262 100644
--- a/drivers/pci/controller/dwc/pcie-designware-debugfs.c
+++ b/drivers/pci/controller/dwc/pcie-designware-debugfs.c
@@ -443,6 +443,72 @@ static ssize_t counter_value_read(struct file *file, char __user *buf,
 	return simple_read_from_buffer(buf, count, ppos, debugfs_buf, pos);
 }
 
+static const char *ltssm_status_string(enum dw_pcie_ltssm ltssm)
+{
+	const char *str;
+
+	switch (ltssm) {
+#define DW_PCIE_LTSSM_NAME(n) case n: str = #n; break
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_DETECT_QUIET);
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_DETECT_ACT);
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_POLL_ACTIVE);
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_POLL_COMPLIANCE);
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_POLL_CONFIG);
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_PRE_DETECT_QUIET);
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_DETECT_WAIT);
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_CFG_LINKWD_START);
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_CFG_LINKWD_ACEPT);
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_CFG_LANENUM_WAI);
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_CFG_LANENUM_ACEPT);
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_CFG_COMPLETE);
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_CFG_IDLE);
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_RCVRY_LOCK);
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_RCVRY_SPEED);
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_RCVRY_RCVRCFG);
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_RCVRY_IDLE);
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_L0);
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_L0S);
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_L123_SEND_EIDLE);
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_L1_IDLE);
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_L2_IDLE);
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_L2_WAKE);
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_DISABLED_ENTRY);
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_DISABLED_IDLE);
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_DISABLED);
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_LPBK_ENTRY);
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_LPBK_ACTIVE);
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_LPBK_EXIT);
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_LPBK_EXIT_TIMEOUT);
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_HOT_RESET_ENTRY);
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_HOT_RESET);
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_RCVRY_EQ0);
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_RCVRY_EQ1);
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_RCVRY_EQ2);
+	DW_PCIE_LTSSM_NAME(DW_PCIE_LTSSM_RCVRY_EQ3);
+	default:
+		str = "DW_PCIE_LTSSM_UNKNOWN";
+		break;
+	}
+
+	return str + strlen("DW_PCIE_LTSSM_");
+}
+
+static int ltssm_status_show(struct seq_file *s, void *v)
+{
+	struct dw_pcie *pci = s->private;
+	enum dw_pcie_ltssm val;
+
+	val = dw_pcie_get_ltssm(pci);
+	seq_printf(s, "%s (0x%02x)\n", ltssm_status_string(val), val);
+
+	return 0;
+}
+
+static int ltssm_status_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, ltssm_status_show, inode->i_private);
+}
+
 #define dwc_debugfs_create(name)			\
 debugfs_create_file(#name, 0644, rasdes_debug, pci,	\
 			&dbg_ ## name ## _fops)
@@ -479,6 +545,11 @@ static const struct file_operations dwc_pcie_counter_value_ops = {
 	.read = counter_value_read,
 };
 
+static const struct file_operations dwc_pcie_ltssm_status_ops = {
+	.open = ltssm_status_open,
+	.read = seq_read,
+};
+
 static void dwc_pcie_rasdes_debugfs_deinit(struct dw_pcie *pci)
 {
 	struct dwc_pcie_rasdes_info *rinfo = pci->debugfs->rasdes_info;
@@ -565,6 +636,12 @@ err_deinit:
 	return ret;
 }
 
+static void dwc_pcie_ltssm_debugfs_init(struct dw_pcie *pci, struct dentry *dir)
+{
+	debugfs_create_file("ltssm_status", 0444, dir, pci,
+			    &dwc_pcie_ltssm_status_ops);
+}
+
 void dwc_pcie_debugfs_deinit(struct dw_pcie *pci)
 {
 	if (!pci->debugfs)
@@ -595,4 +672,6 @@ void dwc_pcie_debugfs_init(struct dw_pcie *pci)
 	if (err)
 		dev_err(dev, "failed to initialize RAS DES debugfs, err=%d\n",
 			err);
+
+	dwc_pcie_ltssm_debugfs_init(pci, dir);
 }
diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
index dd129718fb41..a03b3799fb27 100644
--- a/drivers/pci/controller/dwc/pcie-designware.h
+++ b/drivers/pci/controller/dwc/pcie-designware.h
@@ -330,9 +330,40 @@ enum dw_pcie_ltssm {
 	/* Need to align with PCIE_PORT_DEBUG0 bits 0:5 */
 	DW_PCIE_LTSSM_DETECT_QUIET = 0x0,
 	DW_PCIE_LTSSM_DETECT_ACT = 0x1,
+	DW_PCIE_LTSSM_POLL_ACTIVE = 0x2,
+	DW_PCIE_LTSSM_POLL_COMPLIANCE = 0x3,
+	DW_PCIE_LTSSM_POLL_CONFIG = 0x4,
+	DW_PCIE_LTSSM_PRE_DETECT_QUIET = 0x5,
 	DW_PCIE_LTSSM_DETECT_WAIT = 0x6,
+	DW_PCIE_LTSSM_CFG_LINKWD_START = 0x7,
+	DW_PCIE_LTSSM_CFG_LINKWD_ACEPT = 0x8,
+	DW_PCIE_LTSSM_CFG_LANENUM_WAI = 0x9,
+	DW_PCIE_LTSSM_CFG_LANENUM_ACEPT = 0xa,
+	DW_PCIE_LTSSM_CFG_COMPLETE = 0xb,
+	DW_PCIE_LTSSM_CFG_IDLE = 0xc,
+	DW_PCIE_LTSSM_RCVRY_LOCK = 0xd,
+	DW_PCIE_LTSSM_RCVRY_SPEED = 0xe,
+	DW_PCIE_LTSSM_RCVRY_RCVRCFG = 0xf,
+	DW_PCIE_LTSSM_RCVRY_IDLE = 0x10,
 	DW_PCIE_LTSSM_L0 = 0x11,
+	DW_PCIE_LTSSM_L0S = 0x12,
+	DW_PCIE_LTSSM_L123_SEND_EIDLE = 0x13,
+	DW_PCIE_LTSSM_L1_IDLE = 0x14,
 	DW_PCIE_LTSSM_L2_IDLE = 0x15,
+	DW_PCIE_LTSSM_L2_WAKE = 0x16,
+	DW_PCIE_LTSSM_DISABLED_ENTRY = 0x17,
+	DW_PCIE_LTSSM_DISABLED_IDLE = 0x18,
+	DW_PCIE_LTSSM_DISABLED = 0x19,
+	DW_PCIE_LTSSM_LPBK_ENTRY = 0x1a,
+	DW_PCIE_LTSSM_LPBK_ACTIVE = 0x1b,
+	DW_PCIE_LTSSM_LPBK_EXIT = 0x1c,
+	DW_PCIE_LTSSM_LPBK_EXIT_TIMEOUT = 0x1d,
+	DW_PCIE_LTSSM_HOT_RESET_ENTRY = 0x1e,
+	DW_PCIE_LTSSM_HOT_RESET = 0x1f,
+	DW_PCIE_LTSSM_RCVRY_EQ0 = 0x20,
+	DW_PCIE_LTSSM_RCVRY_EQ1 = 0x21,
+	DW_PCIE_LTSSM_RCVRY_EQ2 = 0x22,
+	DW_PCIE_LTSSM_RCVRY_EQ3 = 0x23,
 
 	DW_PCIE_LTSSM_UNKNOWN = 0xFFFFFFFF,
 };