Panels often supports backlight as specified in a device tree.
Update the drm_panel infrastructure to support this to
simplify the drivers.
With this the panel driver just needs to add the following to the
probe() function:
err = drm_panel_of_backlight(panel);
if (err)
return err;
Then drm_panel will handle all the rest.
There is one caveat with the backlight support.
If drm_panel_(enable|disable) are called multiple times
in row then backlight_(enable|disable) will be called multiple times.
The above will happen when a panel drivers unconditionally
calls drm_panel_disable() in their shutdown() function,
whan the panel is already disabled and then shutdown() is called.
Reading the backlight code it seems safe to call
the backlight_(enable|disable) several times.
v3:
- Improve comments, fix grammar (Laurent)
- Do not fail in drm_panel_of_backlight() if no DT support (Laurent)
- Log if backlight_(enable|disable) fails (Laurent)
- Improve drm_panel_of_backlight() docs
- Updated changelog with backlight analysis (triggered by Laurent)
v2:
- Drop test of CONFIG_DRM_PANEL in header-file (Laurent)
- do not enable backlight if ->enable() returns an error
Signed-off-by: Sam Ravnborg <sam@xxxxxxxxxxxx>
Cc: Thierry Reding <thierry.reding@xxxxxxxxx>
Cc: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
Cc: Maxime Ripard <maxime.ripard@xxxxxxxxxxx>
Cc: Sean Paul <sean@xxxxxxxxxx>
Cc: David Airlie <airlied@xxxxxxxx>
Cc: Daniel Vetter <daniel@xxxxxxxx>
---
drivers/gpu/drm/drm_panel.c | 58 ++++++++++++++++++++++++++++++++++++-
include/drm/drm_panel.h | 25 ++++++++++++++++
2 files changed, 82 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/drm_panel.c b/drivers/gpu/drm/drm_panel.c
index 4ab7229fb22b..c312d5eb214d 100644
--- a/drivers/gpu/drm/drm_panel.c
+++ b/drivers/gpu/drm/drm_panel.c
@@ -21,11 +21,13 @@
* DEALINGS IN THE SOFTWARE.
*/
+#include <linux/backlight.h>
#include <linux/err.h>
#include <linux/module.h>
#include <drm/drm_crtc.h>
#include <drm/drm_panel.h>
+#include <drm/drm_print.h>
static DEFINE_MUTEX(panel_lock);
static LIST_HEAD(panel_list);
@@ -196,11 +198,20 @@ EXPORT_SYMBOL(drm_panel_unprepare);
*/
int drm_panel_enable(struct drm_panel *panel)
{
+ int ret = 0;
+
if (!panel)
return -EINVAL;
if (panel->funcs && panel->funcs->enable)
- return panel->funcs->enable(panel);
+ ret = panel->funcs->enable(panel);
+
+ if (ret < 0)
+ return ret;
+
+ ret = backlight_enable(panel->backlight);
+ if (ret < 0)
+ DRM_DEV_INFO(panel->dev, "failed to enable backlight: %d\n", ret);
return 0;
}
@@ -218,9 +229,15 @@ EXPORT_SYMBOL(drm_panel_enable);
*/
int drm_panel_disable(struct drm_panel *panel)
{
+ int ret;
+
if (!panel)
return -EINVAL;
+ ret = backlight_disable(panel->backlight);
+ if (ret < 0)
+ DRM_DEV_INFO(panel->dev, "failed to disable backlight: %d\n", ret);
+
if (panel->funcs && panel->funcs->disable)
return panel->funcs->disable(panel);
@@ -289,6 +306,45 @@ struct drm_panel *of_drm_find_panel(const struct device_node *np)
EXPORT_SYMBOL(of_drm_find_panel);
#endif
+#ifdef CONFIG_BACKLIGHT_CLASS_DEVICE
+/**
+ * drm_panel_of_backlight - use backlight device node for backlight
+ * @panel: DRM panel
+ *
+ * Use this function to enable backlight handling if your panel
+ * uses device tree and has a backlight phandle.
+ *
+ * When the panel is enabled backlight will be enabled after a
+ * successfull call to &drm_panel_funcs.enable()
+ *
+ * When the panel is disabled backlight will be disabled before the
+ * call to &drm_panel_funcs.disable().
+ *
+ * A typical implementation for a panel driver supporting device tree
+ * will call this function at probe time. Backlight will then be handled
+ * transparently without requiring any intervention from the driver.
+ * drm_panel_of_backlight() must be called after the call to drm_panel_init().
+ *
+ * Return: 0 on success or a negative error code on failure.
+ */
+int drm_panel_of_backlight(struct drm_panel *panel)
+{
+ struct backlight_device *backlight;
+
+ if (!panel || !panel->dev)
+ return -EINVAL;
+
+ backlight = devm_of_find_backlight(panel->dev);
+
+ if (IS_ERR(backlight))
+ return PTR_ERR(backlight);
+
+ panel->backlight = backlight;
+ return 0;
+}
+EXPORT_SYMBOL(drm_panel_of_backlight);
+#endif
+
MODULE_AUTHOR("Thierry Reding <treding@xxxxxxxxxx>");
MODULE_DESCRIPTION("DRM panel infrastructure");
MODULE_LICENSE("GPL and additional rights");
diff --git a/include/drm/drm_panel.h b/include/drm/drm_panel.h
index d71655b2634c..c751c9b17df0 100644
--- a/include/drm/drm_panel.h
+++ b/include/drm/drm_panel.h
@@ -28,6 +28,7 @@
#include <linux/errno.h>
#include <linux/list.h>
+struct backlight_device;
struct device_node;
struct drm_connector;
struct drm_device;
@@ -59,6 +60,10 @@ struct display_timing;
*
* To save power when no video data is transmitted, a driver can power down
* the panel. This is the job of the .unprepare() function.
+ *
+ * Backlight can be handled automatically if configured using
+ * drm_panel_of_backlight(). Then the driver does not need to implement the
+ * functionality to enable/disable backlight.
*/
struct drm_panel_funcs {
/**
@@ -146,6 +151,17 @@ struct drm_panel {
*/
struct device *dev;
+ /**
+ * @backlight:
+ *
+ * Backlight device, used to turn on backlight after the call
+ * to enable(), and to turn off backlight before the call to
+ * disable().
+ * backlight is set by drm_panel_of_backlight() and drivers
+ * shall not assign it.
+ */
+ struct backlight_device *backlight;
+
/**
* @funcs:
*
@@ -197,4 +213,13 @@ static inline struct drm_panel *of_drm_find_panel(const struct device_node *np)
}
#endif
+#if IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE)
+int drm_panel_of_backlight(struct drm_panel *panel);
+#else
+static inline int drm_panel_of_backlight(struct drm_panel *panel)
+{
+ return 0;
+}
+#endif
+
#endif
--
2.20.1
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