[PATCH v4 10/10] pwm-backlight: Add rudimentary device tree support
Thierry Reding
thierry.reding at avionic-design.de
Wed Mar 14 11:56:33 EDT 2012
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.
A pointer to the exit() callback is stored in the driver data to keep it
around until the driver is unloaded.
Signed-off-by: Thierry Reding <thierry.reding at avionic-design.de>
---
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 | 19 +++
drivers/video/backlight/Kconfig | 2 +-
drivers/video/backlight/pwm_bl.c | 136 +++++++++++++++++---
include/linux/pwm_backlight.h | 2 +
4 files changed, 141 insertions(+), 18 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..79db3dd
--- /dev/null
+++ b/Documentation/devicetree/bindings/video/backlight/pwm-backlight
@@ -0,0 +1,19 @@
+pwm-backlight bindings
+
+Required properties:
+ - compatible: "pwm-backlight"
+ - pwm: OF device-tree PWM specification
+ - num-brightness-levels: number of distinct brightness levels
+ - brightness-levels: array of distinct brightness levels
+ - default-brightness-level: the default brightness level
+
+Example:
+
+ backlight {
+ compatible = "pwm-backlight";
+ pwm = <&pwm 0 5000000>;
+
+ num-brightness-levels = <8>;
+ 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..ecfe3a0 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 HAVE_PWM || 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..57ff91b 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -17,6 +17,7 @@
#include <linux/fb.h>
#include <linux/backlight.h>
#include <linux/err.h>
+#include <linux/of_pwm.h>
#include <linux/pwm.h>
#include <linux/pwm_backlight.h>
#include <linux/slab.h>
@@ -26,11 +27,13 @@ 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 +55,11 @@ 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 +91,102 @@ 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 pwm_device *pwm;
+ u32 value;
+ int ret;
+
+ if (!node)
+ return -ENODEV;
+
+ pwm = of_pwm_request(node, "pwm", 0);
+ if (IS_ERR(pwm))
+ return PTR_ERR(pwm);
+
+ memset(data, 0, sizeof(*data));
+ data->pwm_period_ns = pwm_get_period(pwm);
+ data->pwm = pwm;
+
+ ret = of_property_read_u32(node, "num-brightness-levels", &value);
+ if (ret < 0)
+ goto free;
+
+ data->max_brightness = value;
+
+ 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) {
+ ret = -ENOMEM;
+ goto free;
+ }
+
+ ret = of_property_read_u32_array(node, "brightness-levels",
+ data->levels,
+ data->max_brightness);
+ if (ret < 0)
+ goto free;
+
+ ret = of_property_read_u32(node, "default-brightness-level",
+ &value);
+ if (ret < 0)
+ goto free;
+
+ 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;
+
+free:
+ pwm_free(pwm);
+
+ return ret;
+}
+
+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_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 +202,30 @@ static int pwm_backlight_probe(struct platform_device *pdev)
goto err_alloc;
}
+ if (data->levels) {
+ max = data->levels[data->max_brightness];
+ pb->levels = data->levels;
+ } else
+ max = data->max_brightness;
+
pb->period = data->pwm_period_ns;
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->lth_brightness = data->lth_brightness * (data->pwm_period_ns / max);
+ pb->pwm = data->pwm;
pb->dev = &pdev->dev;
- pb->pwm = pwm_request(data->pwm_id, "backlight");
- 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");
+ if (!pb->pwm) {
+ pb->pwm = pwm_request(data->pwm_id, "backlight");
+ 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");
+ }
memset(&props, 0, sizeof(struct backlight_properties));
props.type = BACKLIGHT_RAW;
@@ -152,7 +254,6 @@ 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);
@@ -160,8 +261,8 @@ static int pwm_backlight_remove(struct platform_device *pdev)
pwm_config(pb->pwm, 0, pb->period);
pwm_disable(pb->pwm);
pwm_free(pb->pwm);
- if (data->exit)
- data->exit(&pdev->dev);
+ if (pb->exit)
+ pb->exit(&pdev->dev);
return 0;
}
@@ -195,11 +296,12 @@ 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..3d1f0da 100644
--- a/include/linux/pwm_backlight.h
+++ b/include/linux/pwm_backlight.h
@@ -7,11 +7,13 @@
#include <linux/backlight.h>
struct platform_pwm_backlight_data {
+ struct pwm_device *pwm;
int pwm_id;
unsigned int max_brightness;
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);
--
1.7.9.4
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