drm/amd/display: Add DMUB tracebuffer debugfs

[Why]
The DMUB tracebuffer is useful for understanding DMCUB execution state.

[How]
Add a "show" attribute debugfs so we can loop through the buffer
and print the entries.

The structs for the entry format are defined in the debugfs since
the tracebuffer header no longer exists in the DMUB service.
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Reviewed-by: Hersen Wu <hersenxs.wu@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_debugfs.c

@@ -32,6 +32,19 @@
 #include "amdgpu_dm.h"
 #include "amdgpu_dm_debugfs.h"
 #include "dm_helpers.h"
+#include "dmub/inc/dmub_srv.h"
+
+struct dmub_debugfs_trace_header {
+	uint32_t entry_count;
+	uint32_t reserved[3];
+};
+
+struct dmub_debugfs_trace_entry {
+	uint32_t trace_code;
+	uint32_t tick_count;
+	uint32_t param0;
+	uint32_t param1;
+};
 
 /* function description
  * get/ set DP configuration: lane_count, link_rate, spread_spectrum
@@ -675,6 +688,50 @@ static ssize_t dp_phy_test_pattern_debugfs_write(struct file *f, const char __us
 	return bytes_from_user;
 }
 
+/**
+ * Returns the DMCUB tracebuffer contents.
+ * Example usage: cat /sys/kernel/debug/dri/0/amdgpu_dm_dmub_tracebuffer
+ */
+static int dmub_tracebuffer_show(struct seq_file *m, void *data)
+{
+	struct amdgpu_device *adev = m->private;
+	struct dmub_srv_fb_info *fb_info = adev->dm.dmub_fb_info;
+	struct dmub_debugfs_trace_entry *entries;
+	uint8_t *tbuf_base;
+	uint32_t tbuf_size, max_entries, num_entries, i;
+
+	if (!fb_info)
+		return 0;
+
+	tbuf_base = (uint8_t *)fb_info->fb[DMUB_WINDOW_5_TRACEBUFF].cpu_addr;
+	if (!tbuf_base)
+		return 0;
+
+	tbuf_size = fb_info->fb[DMUB_WINDOW_5_TRACEBUFF].size;
+	max_entries = (tbuf_size - sizeof(struct dmub_debugfs_trace_header)) /
+		      sizeof(struct dmub_debugfs_trace_entry);
+
+	num_entries =
+		((struct dmub_debugfs_trace_header *)tbuf_base)->entry_count;
+
+	num_entries = min(num_entries, max_entries);
+
+	entries = (struct dmub_debugfs_trace_entry
+			   *)(tbuf_base +
+			      sizeof(struct dmub_debugfs_trace_header));
+
+	for (i = 0; i < num_entries; ++i) {
+		struct dmub_debugfs_trace_entry *entry = &entries[i];
+
+		seq_printf(m,
+			   "trace_code=%u tick_count=%u param0=%u param1=%u\n",
+			   entry->trace_code, entry->tick_count, entry->param0,
+			   entry->param1);
+	}
+
+	return 0;
+}
+
 /*
  * Returns the current and maximum output bpc for the connector.
  * Example usage: cat /sys/kernel/debug/dri/0/DP-1/output_bpc
@@ -880,6 +937,7 @@ static ssize_t dp_dpcd_data_read(struct file *f, char __user *buf,
 	return read_size - r;
 }
 
+DEFINE_SHOW_ATTRIBUTE(dmub_tracebuffer);
 DEFINE_SHOW_ATTRIBUTE(output_bpc);
 DEFINE_SHOW_ATTRIBUTE(vrr_range);
 
@@ -1188,5 +1246,8 @@ int dtn_debugfs_init(struct amdgpu_device *adev)
 	debugfs_create_file_unsafe("amdgpu_dm_visual_confirm", 0644, root, adev,
 				   &visual_confirm_fops);
 
+	debugfs_create_file_unsafe("amdgpu_dm_dmub_tracebuffer", 0644, root,
+				   adev, &dmub_tracebuffer_fops);
+
 	return 0;
 }