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@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;
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@xxxxxxxxxxxxxxxx>
> + 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
--
Regards,
Laurent Pinchart
