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Subject[PATCH v6 2/4] pwm_backlight: use power sequences
Date
Make use of the power sequences specified in the device tree or platform
data to control how the backlight is powered on and off.

Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
---
.../bindings/video/backlight/pwm-backlight.txt | 65 +++++++-
drivers/video/backlight/Kconfig | 1 +
drivers/video/backlight/pwm_bl.c | 180 +++++++++++++++------
include/linux/pwm_backlight.h | 15 +-
4 files changed, 208 insertions(+), 53 deletions(-)

diff --git a/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt b/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
index 689c7d2..3b7e99b 100644
--- a/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
+++ b/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
@@ -2,7 +2,8 @@ pwm-backlight bindings

Required properties:
- compatible: "pwm-backlight"
- - pwms: OF device-tree PWM specification (see PWM binding[0])
+ - pwms: OF device-tree PWM specification (see PWM binding[0]). Exactly one PWM
+ must be specified
- 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
@@ -16,17 +17,75 @@ Optional properties:
"pwms" property (see PWM binding[0])
- low_threshold_brightness: brightness threshold low level. (get linear
scales in brightness in low end of brightness levels)
+ - pwm-names: name for the PWM device specified in the "pwms" property (see PWM
+ binding[0]). Necessary if power sequences are used
+ - power-sequences: Power sequences (see Power sequences[1]) used to bring the
+ backlight on and off. If this property is present, then two power
+ sequences named "power-on" and "power-off" must be defined to control how
+ the backlight is to be powered on and off. These sequences must reference
+ the PWM specified in the pwms property by its name, and can also reference
+ other resources supported by the power sequences mechanism

[0]: Documentation/devicetree/bindings/pwm/pwm.txt
+[1]: Documentation/devicetree/bindings/power_seq/power_seq.txt

Example:

backlight {
compatible = "pwm-backlight";
- pwms = <&pwm 0 5000000>;
-
brightness-levels = <0 4 8 16 32 64 128 255>;
default-brightness-level = <6>;
+
+ /* resources used by the sequences */
+ pwms = <&pwm 2 5000000>;
+ pwm-names = "backlight";
+ power-supply = <&backlight_reg>;
+
+ power-sequences {
+ power-on {
+ step0 {
+ type = "regulator";
+ id = "power";
+ enable;
+ };
+ step1 {
+ type = "delay";
+ delay = <10000>;
+ };
+ step2 {
+ type = "pwm";
+ id = "backlight";
+ enable;
+ };
+ step3 {
+ type = "gpio";
+ gpio = <&gpio 28 0>;
+ value = <1>;
+ };
+ };
+
+ power-off {
+ step0 {
+ type = "gpio";
+ gpio = <&gpio 28 0>;
+ value = <0>;
+ };
+ step1 {
+ type = "pwm";
+ id = "backlight";
+ disable;
+ };
+ step2 {
+ type = "delay";
+ delay = <10000>;
+ };
+ step3 {
+ type = "regulator";
+ id = "power";
+ disable;
+ };
+ };
+ };
};

Example for brightness_threshold_level:
diff --git a/drivers/video/backlight/Kconfig b/drivers/video/backlight/Kconfig
index 950a131..ca86125 100644
--- a/drivers/video/backlight/Kconfig
+++ b/drivers/video/backlight/Kconfig
@@ -239,6 +239,7 @@ config BACKLIGHT_CARILLO_RANCH
config BACKLIGHT_PWM
tristate "Generic PWM based Backlight Driver"
depends on PWM
+ select POWER_SEQ
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 4965408..37a23c5 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -27,6 +27,12 @@ struct pwm_bl_data {
unsigned int period;
unsigned int lth_brightness;
unsigned int *levels;
+ bool enabled;
+ struct power_seq_set *power_seqs;
+ struct power_seq *power_on_seq;
+ struct power_seq *power_off_seq;
+
+ /* Legacy callbacks */
int (*notify)(struct device *,
int brightness);
void (*notify_after)(struct device *,
@@ -35,6 +41,52 @@ struct pwm_bl_data {
void (*exit)(struct device *);
};

+static void pwm_backlight_on(struct backlight_device *bl)
+{
+ struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
+ int ret;
+
+ if (pb->enabled)
+ return;
+
+ if (pb->power_seqs) {
+ ret = power_seq_run(pb->power_on_seq);
+ if (ret < 0) {
+ dev_err(&bl->dev, "cannot run power on sequence\n");
+ return;
+ }
+ } else {
+ /* legacy framework */
+ pwm_config(pb->pwm, 0, pb->period);
+ pwm_disable(pb->pwm);
+ }
+
+ pb->enabled = true;
+}
+
+static void pwm_backlight_off(struct backlight_device *bl)
+{
+ struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
+ int ret;
+
+ if (!pb->enabled)
+ return;
+
+ if (pb->power_seqs) {
+ ret = power_seq_run(pb->power_off_seq);
+ if (ret < 0) {
+ dev_err(&bl->dev, "cannot run power off sequence\n");
+ return;
+ }
+ } else {
+ /* legacy framework */
+ pwm_enable(pb->pwm);
+ return;
+ }
+
+ pb->enabled = false;
+}
+
static int pwm_backlight_update_status(struct backlight_device *bl)
{
struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
@@ -51,8 +103,7 @@ static int pwm_backlight_update_status(struct backlight_device *bl)
brightness = pb->notify(pb->dev, brightness);

if (brightness == 0) {
- pwm_config(pb->pwm, 0, pb->period);
- pwm_disable(pb->pwm);
+ pwm_backlight_off(bl);
} else {
int duty_cycle;

@@ -66,7 +117,7 @@ static int pwm_backlight_update_status(struct backlight_device *bl)
duty_cycle = pb->lth_brightness +
(duty_cycle * (pb->period - pb->lth_brightness) / max);
pwm_config(pb->pwm, duty_cycle, pb->period);
- pwm_enable(pb->pwm);
+ pwm_backlight_on(bl);
}

if (pb->notify_after)
@@ -150,12 +201,6 @@ static int pwm_backlight_parse_dt(struct device *dev,
data->lth_brightness = value;
}

- /*
- * 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;
}

@@ -177,33 +222,97 @@ static int pwm_backlight_probe(struct platform_device *pdev)
{
struct platform_pwm_backlight_data *data = pdev->dev.platform_data;
struct platform_pwm_backlight_data defdata;
+ struct power_seq_resource *res;
struct backlight_properties props;
struct backlight_device *bl;
struct pwm_bl_data *pb;
unsigned int max;
int ret;

+ pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL);
+ if (!pb) {
+ dev_err(&pdev->dev, "no memory for state\n");
+ return -ENOMEM;
+ }
+
+ /* using device tree? */
if (!data) {
+ /* build platform data from device tree */
ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
- if (ret < 0) {
+ if (ret == -EPROBE_DEFER) {
+ return ret;
+ } else if (ret < 0) {
dev_err(&pdev->dev, "failed to find platform data\n");
return ret;
}
-
data = &defdata;
}

+ /* using power sequences? */
+ pb->power_seqs = devm_power_seq_set_build(&pdev->dev, data->power_seqs);
+ if (pb->power_seqs) {
+ struct power_seq_set *seqs = pb->power_seqs;
+
+ if (IS_ERR(seqs))
+ return PTR_ERR(seqs);
+
+ pb->power_on_seq = power_seq_lookup(seqs, "power-on");
+ if (!pb->power_on_seq) {
+ dev_err(&pdev->dev, "missing power-on sequence\n");
+ return -EINVAL;
+ }
+ pb->power_off_seq = power_seq_lookup(seqs, "power-off");
+ if (!pb->power_off_seq) {
+ dev_err(&pdev->dev, "missing power-off sequence\n");
+ return -EINVAL;
+ }
+
+ /* we must have exactly one PWM for this driver */
+ power_seq_for_each_resource(res, seqs) {
+ if (res->type != POWER_SEQ_PWM)
+ continue;
+ if (pb->pwm) {
+ dev_err(&pdev->dev, "more than one PWM used\n");
+ return -EINVAL;
+ }
+ /* keep the pwm at hand */
+ pb->pwm = res->pwm.pwm;
+ }
+ }
+ /* using legacy interface? */
+ else {
+ pb->pwm = devm_pwm_get(&pdev->dev, NULL);
+ if (IS_ERR(pb->pwm)) {
+ 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");
+ return PTR_ERR(pb->pwm);
+ }
+ }
+
+ /*
+ * 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);
+ }
+
if (data->init) {
ret = data->init(&pdev->dev);
if (ret < 0)
- return ret;
+ goto err;
}

- pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL);
- if (!pb) {
- dev_err(&pdev->dev, "no memory for state\n");
- ret = -ENOMEM;
- goto err_alloc;
+ /* from here we should have a PWM */
+ if (!pb->pwm) {
+ dev_err(&pdev->dev, "no PWM defined!\n");
+ return -EINVAL;
}

if (data->levels) {
@@ -218,28 +327,6 @@ static int pwm_backlight_probe(struct platform_device *pdev)
pb->exit = data->exit;
pb->dev = &pdev->dev;

- pb->pwm = pwm_get(&pdev->dev, NULL);
- if (IS_ERR(pb->pwm)) {
- 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);

@@ -251,18 +338,17 @@ static int pwm_backlight_probe(struct platform_device *pdev)
if (IS_ERR(bl)) {
dev_err(&pdev->dev, "failed to register backlight\n");
ret = PTR_ERR(bl);
- goto err_bl;
+ goto err;
}

bl->props.brightness = data->dft_brightness;
backlight_update_status(bl);

platform_set_drvdata(pdev, bl);
+
return 0;

-err_bl:
- pwm_put(pb->pwm);
-err_alloc:
+err:
if (data->exit)
data->exit(&pdev->dev);
return ret;
@@ -274,9 +360,8 @@ static int pwm_backlight_remove(struct platform_device *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_put(pb->pwm);
+ pwm_backlight_off(bl);
+
if (pb->exit)
pb->exit(&pdev->dev);
return 0;
@@ -290,8 +375,7 @@ static int pwm_backlight_suspend(struct device *dev)

if (pb->notify)
pb->notify(pb->dev, 0);
- pwm_config(pb->pwm, 0, pb->period);
- pwm_disable(pb->pwm);
+ pwm_backlight_off(bl);
if (pb->notify_after)
pb->notify_after(pb->dev, 0);
return 0;
diff --git a/include/linux/pwm_backlight.h b/include/linux/pwm_backlight.h
index 56f4a86..70d22f2 100644
--- a/include/linux/pwm_backlight.h
+++ b/include/linux/pwm_backlight.h
@@ -5,14 +5,25 @@
#define __LINUX_PWM_BACKLIGHT_H

#include <linux/backlight.h>
+#include <linux/power_seq.h>

struct platform_pwm_backlight_data {
- int pwm_id;
unsigned int max_brightness;
unsigned int dft_brightness;
unsigned int lth_brightness;
- unsigned int pwm_period_ns;
unsigned int *levels;
+ /*
+ * New interface using power sequences
+ */
+ struct platform_power_seq_set *power_seqs;
+ /*
+ * Legacy interface - use power sequences instead!
+ *
+ * pwm_id and pwm_period_ns need only be specified
+ * if get_pwm(dev, NULL) would return NULL.
+ */
+ int pwm_id;
+ unsigned int pwm_period_ns;
int (*init)(struct device *dev);
int (*notify)(struct device *dev, int brightness);
void (*notify_after)(struct device *dev, int brightness);
--
1.7.12


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