drm/xe: Don't fail probe on unsupported mailbox command

If the device is running older pcode firmware, it is possible that newer
mailbox commands are not supported by it. The sysfs attributes aren't
useful in that case, but we shouldn't fail driver probe because of it.
As of now, it is unknown if we can distinguish unsupported commands before
attempting them. But until we figure out a way to do that, fix the
regressions.

v2: Add debug message (Lucas)

Fixes: cdc36b6 ("drm/xe: Expose fan control and voltage regulator version")
Signed-off-by: Raag Jadav <[email protected]>
Tested-by: Matthew Brost <[email protected]>
Reviewed-by: Jonathan Cavitt <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Rodrigo Vivi <[email protected]>
(cherry picked from commit ed5461d)
Signed-off-by: Rodrigo Vivi <[email protected]>

Author: raagjadav

drivers/gpu/drm/xe/xe_device_sysfs.c

@@ -160,8 +160,13 @@ static int late_bind_create_files(struct device *dev)
 
 	ret = xe_pcode_read(root, PCODE_MBOX(PCODE_LATE_BINDING, GET_CAPABILITY_STATUS, 0),
 			    &cap, NULL);
-	if (ret)
+	if (ret) {
+		if (ret == -ENXIO) {
+			drm_dbg(&xe->drm, "Late binding not supported by firmware\n");
+			ret = 0;
+		}
 		goto out;
+	}
 
 	if (REG_FIELD_GET(V1_FAN_SUPPORTED, cap)) {
 		ret = sysfs_create_file(&dev->kobj, &dev_attr_lb_fan_control_version.attr);