[PATCH v2 10/11] video: simple-panel: support panel-lvds DT bindings

simple-panel already parses display-timings, enable-gpios and a
backlight phandle from DT, which is exactly what a Linux panel-lvds
node provides.  Unlike Linux's drivers/gpu/drm/panel/panel-simple.c
we have no hardcoded panel tables, so there's nothing LVDS-specific
left for a dedicated driver to do.  Bring panel-lvds DTs in:

  - Match "panel-lvds" in the of_device_id table.

  - Read modes from a "panel-timing" subnode as a fallback when
    "display-timings" isn't present.  Linux's panel-lvds binding uses
    the singular form; without this, the panel reports "No modes
    found" and the display chain has nothing to allocate a fb for.

  - Switch the power-supply lookup to regulator_get_optional() and
    treat -ENODEV as "no supply".  Many panel-lvds DTs omit
    "power-supply" because the rail is hard-wired; the call sites
    already pass NULL through safely.

Signed-off-by: Johannes Schneider <[email protected]>
---
 drivers/video/simple-panel.c | 23 ++++++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/drivers/video/simple-panel.c b/drivers/video/simple-panel.c
index 63a032a9b8..66d519425a 100644
--- a/drivers/video/simple-panel.c
+++ b/drivers/video/simple-panel.c
@@ -112,6 +112,19 @@ static int simple_panel_get_modes(struct simple_panel *panel, struct display_tim
 		return 0;
 	}
 
+	/* panel-lvds DTs put the single mode in "panel-timing", not "display-timings" */
+	if (of_get_child_by_name(panel->dev->of_node, "panel-timing")) {
+		struct fb_videomode *mode = xzalloc(sizeof(*mode));
+
+		ret = of_get_display_timing(panel->dev->of_node, "panel-timing", mode);
+		if (!ret) {
+			timings->modes = mode;
+			timings->num_modes = 1;
+			return 0;
+		}
+		free(mode);
+	}
+
 	dev_err(panel->dev, "No modes found\n");
 
 	return -ENOENT;
@@ -162,9 +175,12 @@ static int simple_panel_probe(struct device *dev)
 
 	panel->backlight_node = of_parse_phandle(node, "backlight", 0);
 
-	panel->power = regulator_get(dev, "power");
-	if (IS_ERR(panel->power))
-		return dev_errp_probe(dev, panel->power, "Cannot find regulator\n");
+	panel->power = regulator_get_optional(dev, "power");
+	if (IS_ERR(panel->power)) {
+		if (PTR_ERR(panel->power) != -ENODEV)
+			return dev_errp_probe(dev, panel->power, "power supply\n");
+		panel->power = NULL;
+	}
 
 	ret = vpl_register(&panel->vpl);
 	if (ret)
@@ -175,6 +191,7 @@ static int simple_panel_probe(struct device *dev)
 
 static struct of_device_id simple_panel_of_ids[] = {
 	{ .compatible = "simple-panel", },
+	{ .compatible = "panel-lvds", },
 	{ }
 };
 MODULE_DEVICE_TABLE(of, simple_panel_of_ids);
-- 
2.43.0