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SubjectRe: [PATCH v2] drm/panel: rpi-touchscreen: Add backlight support
Date
Nicolas Saenz Julienne <nsaenzjulienne@suse.de> writes:

> This patch exposes backlight control into userspace by creating a
> backlight device instead of directly accessing the PWM registers.
>
> The backlight driver can't go on a separate file as it shares the I2C
> bus & address with the panel.

I remember some concerns from Gordon about exposing the backlight PWM.
Gordon, care to chime in on this?

> Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
> ---
> v1 -> v2:
> - Add Kconfig dependency with BACKLIGHT_CLASS_DEVICE
>
> drivers/gpu/drm/panel/Kconfig | 1 +
> .../drm/panel/panel-raspberrypi-touchscreen.c | 33 +++++++++++++++++--
> 2 files changed, 32 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/panel/Kconfig b/drivers/gpu/drm/panel/Kconfig
> index 6020c30a33b3..1ce35483f342 100644
> --- a/drivers/gpu/drm/panel/Kconfig
> +++ b/drivers/gpu/drm/panel/Kconfig
> @@ -112,6 +112,7 @@ config DRM_PANEL_PANASONIC_VVX10F034N00
> config DRM_PANEL_RASPBERRYPI_TOUCHSCREEN
> tristate "Raspberry Pi 7-inch touchscreen panel"
> depends on DRM_MIPI_DSI
> + depends on BACKLIGHT_CLASS_DEVICE
> help
> Say Y here if you want to enable support for the Raspberry
> Pi 7" Touchscreen. To compile this driver as a module,
> diff --git a/drivers/gpu/drm/panel/panel-raspberrypi-touchscreen.c b/drivers/gpu/drm/panel/panel-raspberrypi-touchscreen.c
> index 2c9c9722734f..838b5c8767bc 100644
> --- a/drivers/gpu/drm/panel/panel-raspberrypi-touchscreen.c
> +++ b/drivers/gpu/drm/panel/panel-raspberrypi-touchscreen.c
> @@ -52,6 +52,7 @@
> #include <linux/of_device.h>
> #include <linux/of_graph.h>
> #include <linux/pm.h>
> +#include <linux/backlight.h>
>
> #include <drm/drm_panel.h>
> #include <drm/drmP.h>
> @@ -196,6 +197,7 @@ struct rpi_touchscreen {
> struct drm_panel base;
> struct mipi_dsi_device *dsi;
> struct i2c_client *i2c;
> + struct backlight_device *backlight;
> };
>
> static const struct drm_display_mode rpi_touchscreen_modes[] = {
> @@ -256,7 +258,8 @@ static int rpi_touchscreen_disable(struct drm_panel *panel)
> {
> struct rpi_touchscreen *ts = panel_to_ts(panel);
>
> - rpi_touchscreen_i2c_write(ts, REG_PWM, 0);
> + ts->backlight->props.brightness = 0;
> + backlight_update_status(ts->backlight);
>
> rpi_touchscreen_i2c_write(ts, REG_POWERON, 0);
> udelay(1);
> @@ -300,7 +303,8 @@ static int rpi_touchscreen_enable(struct drm_panel *panel)
> msleep(100);
>
> /* Turn on the backlight. */
> - rpi_touchscreen_i2c_write(ts, REG_PWM, 255);
> + ts->backlight->props.brightness = 255;
> + backlight_update_status(ts->backlight);
>
> /* Default to the same orientation as the closed source
> * firmware used for the panel. Runtime rotation
> @@ -358,12 +362,26 @@ static const struct drm_panel_funcs rpi_touchscreen_funcs = {
> .get_modes = rpi_touchscreen_get_modes,
> };
>
> +static int raspberrypi_bl_update_status(struct backlight_device *bl)
> +{
> + struct rpi_touchscreen *ts = bl_get_data(bl);
> +
> + rpi_touchscreen_i2c_write(ts, REG_PWM, bl->props.brightness);
> +
> + return 0;
> +}
> +
> +static const struct backlight_ops raspberrypi_bl_ops = {
> + .update_status = raspberrypi_bl_update_status,
> +};
> +
> static int rpi_touchscreen_probe(struct i2c_client *i2c,
> const struct i2c_device_id *id)
> {
> struct device *dev = &i2c->dev;
> struct rpi_touchscreen *ts;
> struct device_node *endpoint, *dsi_host_node;
> + struct backlight_properties props;
> struct mipi_dsi_host *host;
> int ret, ver;
> struct mipi_dsi_device_info info = {
> @@ -398,6 +416,17 @@ static int rpi_touchscreen_probe(struct i2c_client *i2c,
> /* Turn off at boot, so we can cleanly sequence powering on. */
> rpi_touchscreen_i2c_write(ts, REG_POWERON, 0);
>
> + memset(&props, 0, sizeof(props));
> + props.type = BACKLIGHT_RAW;
> + props.max_brightness = 255;
> + ts->backlight = devm_backlight_device_register(dev, dev_name(dev), dev,
> + ts, &raspberrypi_bl_ops,
> + &props);
> + if (IS_ERR(ts->backlight)) {
> + dev_err(dev, "Failed to create backlight device\n");
> + return PTR_ERR(ts->backlight);
> + }
> +
> /* Look up the DSI host. It needs to probe before we do. */
> endpoint = of_graph_get_next_endpoint(dev->of_node, NULL);
> dsi_host_node = of_graph_get_remote_port_parent(endpoint);
> --
> 2.19.2
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