[v2,02/25] drm/panel: add backlight support
diff mbox series

Message ID 20191207140353.23967-3-sam@ravnborg.org
State New
Delegated to: Kieran Bingham
Headers show
Series
  • drm/panel infrastructure + backlight update
Related show

Commit Message

Sam Ravnborg Dec. 7, 2019, 2:03 p.m. UTC
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@ravnborg.org>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <maxime.ripard@bootlin.com>
Cc: Sean Paul <sean@poorly.run>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
---
 drivers/gpu/drm/drm_panel.c | 58 ++++++++++++++++++++++++++++++++++++-
 include/drm/drm_panel.h     | 25 ++++++++++++++++
 2 files changed, 82 insertions(+), 1 deletion(-)

Comments

Laurent Pinchart Dec. 9, 2019, 12:55 a.m. UTC | #1
Hi Sam,

Thank you for the patch.

On Sat, Dec 07, 2019 at 03:03:30PM +0100, Sam Ravnborg wrote:
> Panels often supports backlight as specified in a device tree.

s/supports/support/

> 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.

s/in row/in a row/

> 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@ravnborg.org>
> Cc: Thierry Reding <thierry.reding@gmail.com>
> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Maxime Ripard <maxime.ripard@bootlin.com>
> Cc: Sean Paul <sean@poorly.run>
> Cc: David Airlie <airlied@linux.ie>
> Cc: Daniel Vetter <daniel@ffwll.ch>
> ---
>  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;

You can move this within the above if () block and avoid initializing
ret to 0:

	if (panel->funcs && panel->funcs->enable) {
		ret = panel->funcs->enable(panel);
		if (ret < 0)
			return ret;
	}

With these small issues addressed,

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

> +	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@nvidia.com>");
>  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
Linus Walleij Dec. 13, 2019, 1:30 p.m. UTC | #2
On Sat, Dec 7, 2019 at 3:04 PM Sam Ravnborg <sam@ravnborg.org> wrote:

> 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:

v3 looks good to me +/- Laurent's comments:
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

Yours,
Linus Walleij

Patch
diff mbox series

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@nvidia.com>");
 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