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.
Signed-off-by: Thierry Reding <thierry.reding@xxxxxxxxxxxxxxxxx>
---
Changes in v6:
- don't pass consumer name to pwm_get() because we don't need multiple
PWM devices
- drop num-brightness-levels property because it can be derived from
the brightness-levels property itself
Changes in v5:
- use "pwms" fixed property name
- document brightness-levels and default-brightness-level properties
- check default-brightness-level against brightness-levels
- use new PWM API (pwm_get() and pwm_put()), legacy API (pwm_request())
as fallback
Changes in v4:
- store a PWM requested with of_pwm_request() in the platform data
Changes in v3:
- use a list of distinct brightness levels instead of a linear range
as discussed with Stephen Warren and Mitch Bradley
Changes in v2:
- avoid oops by keeping a reference to the platform-specific exit()
callback
TODO:
- add fixed-regulator support for backlight enable/disable
.../bindings/video/backlight/pwm-backlight | 28 ++++
drivers/video/backlight/Kconfig | 2 +-
drivers/video/backlight/pwm_bl.c | 149 +++++++++++++++++---
include/linux/pwm_backlight.h | 1 +
4 files changed, 159 insertions(+), 21 deletions(-)
create mode 100644 Documentation/devicetree/bindings/video/backlight/pwm-backlight
diff --git a/Documentation/devicetree/bindings/video/backlight/pwm-backlight b/Documentation/devicetree/bindings/video/backlight/pwm-backlight
new file mode 100644
index 0000000..1e4fc72
--- /dev/null
+++ b/Documentation/devicetree/bindings/video/backlight/pwm-backlight
@@ -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 7ed9991..cd77e79 100644
--- a/drivers/video/backlight/Kconfig
+++ b/drivers/video/backlight/Kconfig
@@ -233,7 +233,7 @@ 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);
--
1.7.9.6
--
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