drm/amd/display: Add DMUB firmware state debugfs

[Why]
Firmware state helps to debug sequence issues and hangs for DMCUB
commands and we don't have an easy mechanism to dump it from the driver.

[How]
Add a debugfs entry to dump the current firmware state.
Example usage:

cat /sys/kernel/debug/dri/0/amdgpu_dm_dmub_fw_state
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Reviewed-by: Hersen Wu <hersenxs.wu@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -732,6 +732,29 @@ static int dmub_tracebuffer_show(struct seq_file *m, void *data)
 	return 0;
 }
 
+/**
+ * Returns the DMCUB firmware state contents.
+ * Example usage: cat /sys/kernel/debug/dri/0/amdgpu_dm_dmub_fw_state
+ */
+static int dmub_fw_state_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;
+	uint8_t *state_base;
+	uint32_t state_size;
+
+	if (!fb_info)
+		return 0;
+
+	state_base = (uint8_t *)fb_info->fb[DMUB_WINDOW_6_FW_STATE].cpu_addr;
+	if (!state_base)
+		return 0;
+
+	state_size = fb_info->fb[DMUB_WINDOW_6_FW_STATE].size;
+
+	return seq_write(m, state_base, state_size);
+}
+
 /*
  * Returns the current and maximum output bpc for the connector.
  * Example usage: cat /sys/kernel/debug/dri/0/DP-1/output_bpc
@@ -937,6 +960,7 @@ static ssize_t dp_dpcd_data_read(struct file *f, char __user *buf,
 	return read_size - r;
 }
 
+DEFINE_SHOW_ATTRIBUTE(dmub_fw_state);
 DEFINE_SHOW_ATTRIBUTE(dmub_tracebuffer);
 DEFINE_SHOW_ATTRIBUTE(output_bpc);
 DEFINE_SHOW_ATTRIBUTE(vrr_range);
@@ -1249,5 +1273,8 @@ int dtn_debugfs_init(struct amdgpu_device *adev)
 	debugfs_create_file_unsafe("amdgpu_dm_dmub_tracebuffer", 0644, root,
 				   adev, &dmub_tracebuffer_fops);
 
+	debugfs_create_file_unsafe("amdgpu_dm_dmub_fw_state", 0644, root,
+				   adev, &dmub_fw_state_fops);
+
 	return 0;
 }