From 3e3ed6cdc49d758719c148a78c8b04c243ef74d0 Mon Sep 17 00:00:00 2001 From: Thierry Reding Date: Fri, 16 Dec 2011 21:25:29 +0100 Subject: pwm-backlight: Add rudimentary device tree support This commit adds very basic support for device tree probing. Currently, only a PWM and a list of distinct brightness levels can be specified. Enabling or disabling backlight power via GPIOs is not yet supported. Reviewed-by: Shawn Guo Reviewed-by: Mark Brown Signed-off-by: Thierry Reding diff --git a/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt b/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt new file mode 100644 index 0000000..1e4fc72 --- /dev/null +++ b/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt @@ -0,0 +1,28 @@ +pwm-backlight bindings + +Required properties: + - compatible: "pwm-backlight" + - pwms: OF device-tree PWM specification (see PWM binding[0]) + - brightness-levels: Array of distinct brightness levels. Typically these + are in the range from 0 to 255, but any range starting at 0 will do. + The actual brightness level (PWM duty cycle) will be interpolated + from these values. 0 means a 0% duty cycle (darkest/off), while the + last value in the array represents a 100% duty cycle (brightest). + - default-brightness-level: the default brightness level (index into the + array defined by the "brightness-levels" property) + +Optional properties: + - pwm-names: a list of names for the PWM devices specified in the + "pwms" property (see PWM binding[0]) + +[0]: Documentation/devicetree/bindings/pwm/pwm.txt + +Example: + + backlight { + compatible = "pwm-backlight"; + pwms = <&pwm 0 5000000>; + + brightness-levels = <0 4 8 16 32 64 128 255>; + default-brightness-level = <6>; + }; diff --git a/drivers/video/backlight/Kconfig b/drivers/video/backlight/Kconfig index fa2b037..4c9c022 100644 --- a/drivers/video/backlight/Kconfig +++ b/drivers/video/backlight/Kconfig @@ -245,7 +245,7 @@ config BACKLIGHT_CARILLO_RANCH config BACKLIGHT_PWM tristate "Generic PWM based Backlight Driver" - depends on HAVE_PWM + depends on PWM help If you have a LCD backlight adjustable by PWM, say Y to enable this driver. diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c index 342b7d7..057389d 100644 --- a/drivers/video/backlight/pwm_bl.c +++ b/drivers/video/backlight/pwm_bl.c @@ -26,11 +26,13 @@ struct pwm_bl_data { struct device *dev; unsigned int period; unsigned int lth_brightness; + unsigned int *levels; int (*notify)(struct device *, int brightness); void (*notify_after)(struct device *, int brightness); int (*check_fb)(struct device *, struct fb_info *); + void (*exit)(struct device *); }; static int pwm_backlight_update_status(struct backlight_device *bl) @@ -52,6 +54,11 @@ static int pwm_backlight_update_status(struct backlight_device *bl) pwm_config(pb->pwm, 0, pb->period); pwm_disable(pb->pwm); } else { + if (pb->levels) { + brightness = pb->levels[brightness]; + max = pb->levels[max]; + } + brightness = pb->lth_brightness + (brightness * (pb->period - pb->lth_brightness) / max); pwm_config(pb->pwm, brightness, pb->period); @@ -83,17 +90,98 @@ static const struct backlight_ops pwm_backlight_ops = { .check_fb = pwm_backlight_check_fb, }; +#ifdef CONFIG_OF +static int pwm_backlight_parse_dt(struct device *dev, + struct platform_pwm_backlight_data *data) +{ + struct device_node *node = dev->of_node; + struct property *prop; + int length; + u32 value; + int ret; + + if (!node) + return -ENODEV; + + memset(data, 0, sizeof(*data)); + + /* determine the number of brightness levels */ + prop = of_find_property(node, "brightness-levels", &length); + if (!prop) + return -EINVAL; + + data->max_brightness = length / sizeof(u32); + + /* read brightness levels from DT property */ + if (data->max_brightness > 0) { + size_t size = sizeof(*data->levels) * data->max_brightness; + + data->levels = devm_kzalloc(dev, size, GFP_KERNEL); + if (!data->levels) + return -ENOMEM; + + ret = of_property_read_u32_array(node, "brightness-levels", + data->levels, + data->max_brightness); + if (ret < 0) + return ret; + + ret = of_property_read_u32(node, "default-brightness-level", + &value); + if (ret < 0) + return ret; + + if (value >= data->max_brightness) { + dev_warn(dev, "invalid default brightness level: %u, using %u\n", + value, data->max_brightness - 1); + value = data->max_brightness - 1; + } + + data->dft_brightness = value; + data->max_brightness--; + } + + /* + * TODO: Most users of this driver use a number of GPIOs to control + * backlight power. Support for specifying these needs to be + * added. + */ + + return 0; +} + +static struct of_device_id pwm_backlight_of_match[] = { + { .compatible = "pwm-backlight" }, + { } +}; + +MODULE_DEVICE_TABLE(of, pwm_backlight_of_match); +#else +static int pwm_backlight_parse_dt(struct device *dev, + struct platform_pwm_backlight_data *data) +{ + return -ENODEV; +} +#endif + static int pwm_backlight_probe(struct platform_device *pdev) { - struct backlight_properties props; struct platform_pwm_backlight_data *data = pdev->dev.platform_data; + struct platform_pwm_backlight_data defdata; + struct backlight_properties props; struct backlight_device *bl; struct pwm_bl_data *pb; + unsigned int max; int ret; if (!data) { - dev_err(&pdev->dev, "failed to find platform data\n"); - return -EINVAL; + ret = pwm_backlight_parse_dt(&pdev->dev, &defdata); + if (ret < 0) { + dev_err(&pdev->dev, "failed to find platform data\n"); + return ret; + } + + data = &defdata; } if (data->init) { @@ -109,21 +197,42 @@ static int pwm_backlight_probe(struct platform_device *pdev) goto err_alloc; } - pb->period = data->pwm_period_ns; + if (data->levels) { + max = data->levels[data->max_brightness]; + pb->levels = data->levels; + } else + max = data->max_brightness; + pb->notify = data->notify; pb->notify_after = data->notify_after; pb->check_fb = data->check_fb; - pb->lth_brightness = data->lth_brightness * - (data->pwm_period_ns / data->max_brightness); + pb->exit = data->exit; pb->dev = &pdev->dev; - pb->pwm = pwm_request(data->pwm_id, "backlight"); + pb->pwm = pwm_get(&pdev->dev, NULL); if (IS_ERR(pb->pwm)) { - dev_err(&pdev->dev, "unable to request PWM for backlight\n"); - ret = PTR_ERR(pb->pwm); - goto err_alloc; - } else - dev_dbg(&pdev->dev, "got pwm for backlight\n"); + dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n"); + + pb->pwm = pwm_request(data->pwm_id, "pwm-backlight"); + if (IS_ERR(pb->pwm)) { + dev_err(&pdev->dev, "unable to request legacy PWM\n"); + ret = PTR_ERR(pb->pwm); + goto err_alloc; + } + } + + dev_dbg(&pdev->dev, "got pwm for backlight\n"); + + /* + * The DT case will set the pwm_period_ns field to 0 and store the + * period, parsed from the DT, in the PWM device. For the non-DT case, + * set the period from platform data. + */ + if (data->pwm_period_ns > 0) + pwm_set_period(pb->pwm, data->pwm_period_ns); + + pb->period = pwm_get_period(pb->pwm); + pb->lth_brightness = data->lth_brightness * (pb->period / max); memset(&props, 0, sizeof(struct backlight_properties)); props.type = BACKLIGHT_RAW; @@ -143,7 +252,7 @@ static int pwm_backlight_probe(struct platform_device *pdev) return 0; err_bl: - pwm_free(pb->pwm); + pwm_put(pb->pwm); err_alloc: if (data->exit) data->exit(&pdev->dev); @@ -152,16 +261,15 @@ err_alloc: static int pwm_backlight_remove(struct platform_device *pdev) { - struct platform_pwm_backlight_data *data = pdev->dev.platform_data; struct backlight_device *bl = platform_get_drvdata(pdev); struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev); backlight_device_unregister(bl); pwm_config(pb->pwm, 0, pb->period); pwm_disable(pb->pwm); - pwm_free(pb->pwm); - if (data->exit) - data->exit(&pdev->dev); + pwm_put(pb->pwm); + if (pb->exit) + pb->exit(&pdev->dev); return 0; } @@ -195,11 +303,12 @@ static SIMPLE_DEV_PM_OPS(pwm_backlight_pm_ops, pwm_backlight_suspend, static struct platform_driver pwm_backlight_driver = { .driver = { - .name = "pwm-backlight", - .owner = THIS_MODULE, + .name = "pwm-backlight", + .owner = THIS_MODULE, #ifdef CONFIG_PM - .pm = &pwm_backlight_pm_ops, + .pm = &pwm_backlight_pm_ops, #endif + .of_match_table = of_match_ptr(pwm_backlight_of_match), }, .probe = pwm_backlight_probe, .remove = pwm_backlight_remove, diff --git a/include/linux/pwm_backlight.h b/include/linux/pwm_backlight.h index 63d2df4..56f4a86 100644 --- a/include/linux/pwm_backlight.h +++ b/include/linux/pwm_backlight.h @@ -12,6 +12,7 @@ struct platform_pwm_backlight_data { unsigned int dft_brightness; unsigned int lth_brightness; unsigned int pwm_period_ns; + unsigned int *levels; int (*init)(struct device *dev); int (*notify)(struct device *dev, int brightness); void (*notify_after)(struct device *dev, int brightness); -- cgit v0.10.2