Re: [PATCH 08/10] pwm-backlight: Use new enable_gpio field
On Tue, Oct 01, 2013 at 12:39:36PM -0600, Stephen Warren wrote:
> On 09/23/2013 03:41 PM, Thierry Reding wrote:
> > Make use of the new enable_gpio field and allow it to be set from DT as
> > well. Now that all legacy users of platform data have been converted to
> > initialize this field to an invalid value, it is safe to use the field
> > from the driver.
>
> > diff --git
> > a/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
> > b/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
>
> > Optional properties:
>
> > + - enable-gpios: a list of GPIOs to enable and disable the backlight
>
> That seems to imply that multiple GPIOs are legal. Was that intended? If
> not, I would suggest:
>
> - enable-gpios: contains a single GPIO specifier for the GPIO which
> enables/disables the backlight. See [1] for the format.
>
> >
> > [0]: Documentation/devicetree/bindings/pwm/pwm.txt
> + [1]: Documentation/devicetree/bindings/gpio/gpio.txt
Yes, that sounds better. Indeed only a single GPIO is supported. Adding
more than one would require representing the timing between the two and
that will take us back to where we left off with the power sequences.
> > diff --git a/drivers/video/backlight/pwm_bl.c
> > b/drivers/video/backlight/pwm_bl.c
>
> > @@ -51,12 +55,27 @@ static void pwm_backlight_power_on(struct pwm_bl_data
> > *pb, int brightness,
> > pb->lth_brightness;
> >
> > pwm_config(pb->pwm, duty_cycle, pb->period);
> > +
> > + if (gpio_is_valid(pb->enable_gpio)) {
> > + if (pb->enable_gpio_flags & PWM_BACKLIGHT_GPIO_ACTIVE_LOW)
> > + gpio_set_value(pb->enable_gpio, 0);
> > + else
> > + gpio_set_value(pb->enable_gpio, 1);
> > + }
>
> Feel completely free to ignore this, but when the difference in two
> code-paths is solely in function parameters, I prefer to calculate the
> parameter inside the if statement, then call the function outside the
> conditional code, to highlight the common/different parts:
>
> int value;
>
> /* or an if statement for the next 1 line, if you don't like ?: */
> value = (pb->enable_gpio_flags & PWM_BACKLIGHT_GPIO_ACTIVE_LOW) ? 0 : 1;
> gpio_set_value((pb->enable_gpio, value);
I actually tried that, but it looked cluttered, so I opted for the
alternative. Not that this matters all that much, because beginning with
3.13 the GPIO subsystem should be able to handle the active low flag
internally using the new gpiod_*() API. I plan on converting the driver
to use that during the next cycle.
> > @@ -148,11 +168,10 @@ static int pwm_backlight_parse_dt(struct device *dev,
>
> > + data->enable_gpio = of_get_named_gpio_flags(node, "enable-gpios", 0,
> > + &flags);
> > + if (gpio_is_valid(data->enable_gpio) && (flags & OF_GPIO_ACTIVE_LOW))
> > + data->enable_gpio_flags |= PWM_BACKLIGHT_GPIO_ACTIVE_LOW;
>
> This doesn't seem to handle deferred probe correctly; I would expect
> something more like:
>
> data->enable_gpio = of_get_named_gpio_flags(...);
> if (data->enable_gpio == -EPROBE_DEFERRED)
> return data->enable_gpio;
> if (gpio_is_valid(...))
> ...
> return 0;
>
> I suppose it's possible that the value filters down to
> gpio_request_one() and this actually does work out OK, but that feels
> very accidental/implicit to me.
Yes, I think it does indeed propagate to gpio_request_one(), but you're
right, it should be caught explicitly.
Thierry
pgpHbIXahcrNZ.pgp
Description: PGP signature
Re: [PATCH 08/10] pwm-backlight: Use new enable_gpio field
On 09/23/2013 03:41 PM, Thierry Reding wrote:
> Make use of the new enable_gpio field and allow it to be set from DT as
> well. Now that all legacy users of platform data have been converted to
> initialize this field to an invalid value, it is safe to use the field
> from the driver.
> diff --git
> a/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
> b/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
> Optional properties:
> + - enable-gpios: a list of GPIOs to enable and disable the backlight
That seems to imply that multiple GPIOs are legal. Was that intended? If
not, I would suggest:
- enable-gpios: contains a single GPIO specifier for the GPIO which
enables/disables the backlight. See [1] for the format.
>
> [0]: Documentation/devicetree/bindings/pwm/pwm.txt
+ [1]: Documentation/devicetree/bindings/gpio/gpio.txt
> diff --git a/drivers/video/backlight/pwm_bl.c
> b/drivers/video/backlight/pwm_bl.c
> @@ -51,12 +55,27 @@ static void pwm_backlight_power_on(struct pwm_bl_data
> *pb, int brightness,
>pb->lth_brightness;
>
> pwm_config(pb->pwm, duty_cycle, pb->period);
> +
> + if (gpio_is_valid(pb->enable_gpio)) {
> + if (pb->enable_gpio_flags & PWM_BACKLIGHT_GPIO_ACTIVE_LOW)
> + gpio_set_value(pb->enable_gpio, 0);
> + else
> + gpio_set_value(pb->enable_gpio, 1);
> + }
Feel completely free to ignore this, but when the difference in two
code-paths is solely in function parameters, I prefer to calculate the
parameter inside the if statement, then call the function outside the
conditional code, to highlight the common/different parts:
int value;
/* or an if statement for the next 1 line, if you don't like ?: */
value = (pb->enable_gpio_flags & PWM_BACKLIGHT_GPIO_ACTIVE_LOW) ? 0 : 1;
gpio_set_value((pb->enable_gpio, value);
> @@ -148,11 +168,10 @@ static int pwm_backlight_parse_dt(struct device *dev,
> + data->enable_gpio = of_get_named_gpio_flags(node, "enable-gpios", 0,
> + &flags);
> + if (gpio_is_valid(data->enable_gpio) && (flags & OF_GPIO_ACTIVE_LOW))
> + data->enable_gpio_flags |= PWM_BACKLIGHT_GPIO_ACTIVE_LOW;
This doesn't seem to handle deferred probe correctly; I would expect
something more like:
data->enable_gpio = of_get_named_gpio_flags(...);
if (data->enable_gpio == -EPROBE_DEFERRED)
return data->enable_gpio;
if (gpio_is_valid(...))
...
return 0;
I suppose it's possible that the value filters down to
gpio_request_one() and this actually does work out OK, but that feels
very accidental/implicit to me.
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[PATCH 08/10] pwm-backlight: Use new enable_gpio field
Make use of the new enable_gpio field and allow it to be set from DT as
well. Now that all legacy users of platform data have been converted to
initialize this field to an invalid value, it is safe to use the field
from the driver.
Signed-off-by: Thierry Reding
---
.../bindings/video/backlight/pwm-backlight.txt | 3 ++
drivers/video/backlight/pwm_bl.c | 54 +++---
2 files changed, 50 insertions(+), 7 deletions(-)
diff --git
a/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
b/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
index 1e4fc72..052eb03 100644
--- a/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
+++ b/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
@@ -14,6 +14,7 @@ Required properties:
Optional properties:
- pwm-names: a list of names for the PWM devices specified in the
"pwms" property (see PWM binding[0])
+ - enable-gpios: a list of GPIOs to enable and disable the backlight
[0]: Documentation/devicetree/bindings/pwm/pwm.txt
@@ -25,4 +26,6 @@ Example:
brightness-levels = <0 4 8 16 32 64 128 255>;
default-brightness-level = <6>;
+
+ enable-gpios = <&gpio 58 0>;
};
diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index 8a49b30..506810c 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -10,6 +10,8 @@
* published by the Free Software Foundation.
*/
+#include
+#include
#include
#include
#include
@@ -27,6 +29,8 @@ struct pwm_bl_data {
unsigned intperiod;
unsigned intlth_brightness;
unsigned int*levels;
+ int enable_gpio;
+ unsigned long enable_gpio_flags;
int (*notify)(struct device *,
int brightness);
void(*notify_after)(struct device *,
@@ -51,12 +55,27 @@ static void pwm_backlight_power_on(struct pwm_bl_data *pb,
int brightness,
pb->lth_brightness;
pwm_config(pb->pwm, duty_cycle, pb->period);
+
+ if (gpio_is_valid(pb->enable_gpio)) {
+ if (pb->enable_gpio_flags & PWM_BACKLIGHT_GPIO_ACTIVE_LOW)
+ gpio_set_value(pb->enable_gpio, 0);
+ else
+ gpio_set_value(pb->enable_gpio, 1);
+ }
+
pwm_enable(pb->pwm);
}
static void pwm_backlight_power_off(struct pwm_bl_data *pb)
{
pwm_disable(pb->pwm);
+
+ if (gpio_is_valid(pb->enable_gpio)) {
+ if (pb->enable_gpio_flags & PWM_BACKLIGHT_GPIO_ACTIVE_LOW)
+ gpio_set_value(pb->enable_gpio, 1);
+ else
+ gpio_set_value(pb->enable_gpio, 0);
+ }
}
static int pwm_backlight_update_status(struct backlight_device *bl)
@@ -108,6 +127,7 @@ static int pwm_backlight_parse_dt(struct device *dev,
struct platform_pwm_backlight_data *data)
{
struct device_node *node = dev->of_node;
+ enum of_gpio_flags flags;
struct property *prop;
int length;
u32 value;
@@ -148,11 +168,10 @@ static int pwm_backlight_parse_dt(struct device *dev,
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.
-*/
+ data->enable_gpio = of_get_named_gpio_flags(node, "enable-gpios", 0,
+ &flags);
+ if (gpio_is_valid(data->enable_gpio) && (flags & OF_GPIO_ACTIVE_LOW))
+ data->enable_gpio_flags |= PWM_BACKLIGHT_GPIO_ACTIVE_LOW;
return 0;
}
@@ -210,12 +229,30 @@ static int pwm_backlight_probe(struct platform_device
*pdev)
} else
max = data->max_brightness;
+ pb->enable_gpio = data->enable_gpio;
+ pb->enable_gpio_flags = data->enable_gpio_flags;
pb->notify = data->notify;
pb->notify_after = data->notify_after;
pb->check_fb = data->check_fb;
pb->exit = data->exit;
pb->dev = &pdev->dev;
+ if (gpio_is_valid(pb->enable_gpio)) {
+ unsigned long flags;
+
+ if (pb->enable_gpio_flags & PWM_BACKLIGHT_GPIO_ACTIVE_LOW)
+ flags = GPIOF_OUT_INIT_HIGH;
+ else
+ flags = GPIOF_OUT_INIT_LOW;
+
+ ret = gpio_request_one(pb->enable_gpio, flags, "enable");
+ if (ret < 0) {
+ dev_err(&pdev->dev, "failed to request GPIO#%d: %d\n",
+ pb->enable_gpio, ret);
+ goto err_alloc;
+ }
+ }
+
pb->pwm = dev
