[PATCH 1/2] PCI: dwc: Add LTSSM tracing support to debugfs

[Shawn Lin]

Some platforms may provide LTSSM trace functionality, recording historical
LTSSM state transition information. This is very useful for debugging, such
as when certain devices cannot be recognized. Add an ltssm_trace operation
node in debugfs for platform which could provide these information to show
the LTSSM history.

Signed-off-by: Shawn Lin <shawn.lin at rock-chips.com>
---
 .../controller/dwc/pcie-designware-debugfs.c  | 44 +++++++++++++++++++
 drivers/pci/controller/dwc/pcie-designware.h  |  6 +++
 2 files changed, 50 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-designware-debugfs.c b/drivers/pci/controller/dwc/pcie-designware-debugfs.c
index df98fee69892..569e8e078ef2 100644
--- a/drivers/pci/controller/dwc/pcie-designware-debugfs.c
+++ b/drivers/pci/controller/dwc/pcie-designware-debugfs.c
@@ -511,6 +511,38 @@ static int ltssm_status_open(struct inode *inode, struct file *file)
 	return single_open(file, ltssm_status_show, inode->i_private);
 }
 
+static struct dw_pcie_ltssm_history *dw_pcie_ltssm_trace(struct dw_pcie *pci)
+{
+	if (pci->ops && pci->ops->ltssm_trace)
+		return pci->ops->ltssm_trace(pci);
+
+	return NULL;
+}
+
+static int ltssm_trace_show(struct seq_file *s, void *v)
+{
+	struct dw_pcie *pci = s->private;
+	struct dw_pcie_ltssm_history *history;
+	enum dw_pcie_ltssm val;
+	u32 loop;
+
+	history = dw_pcie_ltssm_trace(pci);
+	if (!history)
+		return 0;
+
+	for (loop = 0; loop < history->count; loop++) {
+		val = history->states[loop];
+		seq_printf(s, "%s (0x%02x)\n", ltssm_status_string(val), val);
+	}
+
+	return 0;
+}
+
+static int ltssm_trace_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, ltssm_trace_show, inode->i_private);
+}
+
 #define dwc_debugfs_create(name)			\
 debugfs_create_file(#name, 0644, rasdes_debug, pci,	\
 			&dbg_ ## name ## _fops)
@@ -552,6 +584,11 @@ static const struct file_operations dwc_pcie_ltssm_status_ops = {
 	.read = seq_read,
 };
 
+static const struct file_operations dwc_pcie_ltssm_trace_ops = {
+	.open = ltssm_trace_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;
@@ -644,6 +681,12 @@ static void dwc_pcie_ltssm_debugfs_init(struct dw_pcie *pci, struct dentry *dir)
 			    &dwc_pcie_ltssm_status_ops);
 }
 
+static void dwc_pcie_ltssm_trace_debugfs_init(struct dw_pcie *pci, struct dentry *dir)
+{
+	debugfs_create_file("ltssm_trace", 0444, dir, pci,
+			    &dwc_pcie_ltssm_trace_ops);
+}
+
 static int dw_pcie_ptm_check_capability(void *drvdata)
 {
 	struct dw_pcie *pci = drvdata;
@@ -922,6 +965,7 @@ void dwc_pcie_debugfs_init(struct dw_pcie *pci, enum dw_pcie_device_mode mode)
 			err);
 
 	dwc_pcie_ltssm_debugfs_init(pci, dir);
+	dwc_pcie_ltssm_trace_debugfs_init(pci, dir);
 
 	pci->mode = mode;
 	pci->ptm_debugfs = pcie_ptm_create_debugfs(pci->dev, pci,
diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
index 5cd27f5739f1..0df18995b7fe 100644
--- a/drivers/pci/controller/dwc/pcie-designware.h
+++ b/drivers/pci/controller/dwc/pcie-designware.h
@@ -395,6 +395,11 @@ enum dw_pcie_ltssm {
 	DW_PCIE_LTSSM_UNKNOWN = 0xFFFFFFFF,
 };
 
+struct dw_pcie_ltssm_history {
+    enum dw_pcie_ltssm *states;
+    u32 count;
+};
+
 struct dw_pcie_ob_atu_cfg {
 	int index;
 	int type;
@@ -499,6 +504,7 @@ struct dw_pcie_ops {
 			      size_t size, u32 val);
 	bool	(*link_up)(struct dw_pcie *pcie);
 	enum dw_pcie_ltssm (*get_ltssm)(struct dw_pcie *pcie);
+	struct dw_pcie_ltssm_history * (*ltssm_trace)(struct dw_pcie *pcie);
 	int	(*start_link)(struct dw_pcie *pcie);
 	void	(*stop_link)(struct dw_pcie *pcie);
 	int	(*assert_perst)(struct dw_pcie *pcie, bool assert);
-- 
2.43.0