[PATCH 1/4] drm/panel: use fwnode based lookups for panel followers

[Lee, Shawn C]

On June 6, 2025, 9:05, Jani Nikula <jani.nikula at intel.com> wrote:
>Use firmware node based lookups for panel followers, to make the code independent of OF and device tree, and make it work also for ACPI with an appropriate _DSD.
>
>ASL example:
>
>	Package (0x02)
>	{
>		"panel", \_SB.PCI0.GFX0.LCD0
>	}
>
>Suggested-by: Heikki Krogerus <heikki.krogerus at linux.intel.com>
>Cc: Neil Armstrong <neil.armstrong at linaro.org>
>Cc: Jessica Zhang <jessica.zhang at oss.qualcomm.com>
>Cc: Maxime Ripard <mripard at kernel.org>
>Cc: Doug Anderson <dianders at chromium.org>
>Cc: Lee Shawn C <shawn.c.lee at intel.com>
>Signed-off-by: Jani Nikula <jani.nikula at intel.com>

This patch series was tested on my local device. And panel follower works well.

Tested-by: Lee Shawn C <shawn.c.lee at intel.com>

>---
> drivers/gpu/drm/drm_panel.c | 39 +++++++++++++++++++++++++++++--------
> 1 file changed, 31 insertions(+), 8 deletions(-)
>
>diff --git a/drivers/gpu/drm/drm_panel.c b/drivers/gpu/drm/drm_panel.c index fee65dc65979..3eb0a615f7a9 100644
>--- a/drivers/gpu/drm/drm_panel.c
>+++ b/drivers/gpu/drm/drm_panel.c
>@@ -473,17 +473,40 @@ int of_drm_get_panel_orientation(const struct device_node *np,  EXPORT_SYMBOL(of_drm_get_panel_orientation);
> #endif
> 
>-static struct drm_panel *of_find_panel(struct device *follower_dev)
>+/* Find panel by fwnode */
>+static struct drm_panel *find_panel_by_fwnode(const struct 
>+fwnode_handle *fwnode)
> {
>-	struct device_node *panel_np;
> 	struct drm_panel *panel;
> 
>-	panel_np = of_parse_phandle(follower_dev->of_node, "panel", 0);
>-	if (!panel_np)
>+	if (!fwnode_device_is_available(fwnode))
> 		return ERR_PTR(-ENODEV);
> 
>-	panel = of_drm_find_panel(panel_np);
>-	of_node_put(panel_np);
>+	mutex_lock(&panel_lock);
>+
>+	list_for_each_entry(panel, &panel_list, list) {
>+		if (dev_fwnode(panel->dev) == fwnode) {
>+			mutex_unlock(&panel_lock);
>+			return panel;
>+		}
>+	}
>+
>+	mutex_unlock(&panel_lock);
>+
>+	return ERR_PTR(-EPROBE_DEFER);
>+}
>+
>+/* Find panel by follower device */
>+static struct drm_panel *find_panel_by_dev(struct device *follower_dev) 
>+{
>+	struct fwnode_handle *fwnode;
>+	struct drm_panel *panel;
>+
>+	fwnode = fwnode_find_reference(dev_fwnode(follower_dev), "panel", 0);
>+	if (IS_ERR_OR_NULL(fwnode))
>+		return ERR_PTR(-ENODEV);
>+
>+	panel = find_panel_by_fwnode(fwnode);
>+	fwnode_handle_put(fwnode);
> 
> 	return panel;
> }
>@@ -506,7 +529,7 @@ bool drm_is_panel_follower(struct device *dev)
> 	 * don't bother trying to parse it here. We just need to know if the
> 	 * property is there.
> 	 */
>-	return of_property_present(dev->of_node, "panel");
>+	return device_property_present(dev, "panel");
> }
> EXPORT_SYMBOL(drm_is_panel_follower);
> 
>@@ -536,7 +559,7 @@ int drm_panel_add_follower(struct device *follower_dev,
> 	struct drm_panel *panel;
> 	int ret;
> 
>-	panel = of_find_panel(follower_dev);
>+	panel = find_panel_by_dev(follower_dev);
> 	if (IS_ERR(panel))
> 		return PTR_ERR(panel);
> 
>--
>2.39.5
>