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Date:   Mon, 15 Jul 2019 10:24:00 +0100
From:   Daniel Thompson <daniel.thompson@linaro.org>
To:     Jean-Jacques Hiblot <jjhiblot@ti.com>
Cc:     Dan Murphy <dmurphy@ti.com>, jacek.anaszewski@gmail.com,
        pavel@ucw.cz, robh+dt@kernel.org, mark.rutland@arm.com,
        linux-leds@vger.kernel.org, linux-kernel@vger.kernel.org,
        devicetree@vger.kernel.org
Subject: Re: [PATCH 1/2] leds: Add control of the voltage/current regulator
 to the LED core
Message-ID: <20190715092400.sedjumqkecglheyu@holly.lan>
References: <20190708103547.23528-1-jjhiblot@ti.com>
 <20190708103547.23528-2-jjhiblot@ti.com>
 <56d16260-ff82-3439-4c1f-2a3a1552bc7d@ti.com>
 <ab4818c0-bc7a-13e1-c6ce-e977b0234de0@ti.com>
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On Mon, Jul 15, 2019 at 11:01:29AM +0200, Jean-Jacques Hiblot wrote:
> Hi Dan,
> 
> On 12/07/2019 20:49, Dan Murphy wrote:
> > JJ
> > 
> > On 7/8/19 5:35 AM, Jean-Jacques Hiblot wrote:
> > > A LED is usually powered by a voltage/current regulator. Let the LED
> > > core
> > Let the LED core know
> > > about it. This allows the LED core to turn on or off the power supply
> > > as needed.
> > 
> > > 
> > > Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
> > > ---
> > > ? drivers/leds/led-class.c | 10 ++++++++
> > > ? drivers/leds/led-core.c? | 53 +++++++++++++++++++++++++++++++++++++---
> > > ? include/linux/leds.h???? |? 4 +++
> > > ? 3 files changed, 64 insertions(+), 3 deletions(-)
> > > 
> > > diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
> > > index 4793e77808e2..e01b2d982564 100644
> > > --- a/drivers/leds/led-class.c
> > > +++ b/drivers/leds/led-class.c
> > > @@ -17,6 +17,7 @@
> > > ? #include <linux/slab.h>
> > > ? #include <linux/spinlock.h>
> > > ? #include <linux/timer.h>
> > > +#include <linux/regulator/consumer.h>
> > 
> > What if you move this to leds.h so core and class can both include it.
> > 
> > 
> > > ? #include <uapi/linux/uleds.h>
> > > ? #include "leds.h"
> > > ? @@ -272,6 +273,15 @@ int of_led_classdev_register(struct device
> > > *parent, struct device_node *np,
> > > ????????? dev_warn(parent, "Led %s renamed to %s due to name collision",
> > > ????????????????? led_cdev->name, dev_name(led_cdev->dev));
> > > ? +??? led_cdev->regulator = devm_regulator_get(led_cdev->dev, "power");
> > 
> > Is the regulator always going to be called power?
> 
> Actually in the dts, that will be "power-supply". I lacked the imagination
> to come up with a better name.
> 
> 
> 
> > 
> > > +??? if (IS_ERR(led_cdev->regulator)) {
> > > +??????? dev_err(led_cdev->dev, "Cannot get the power supply for %s\n",
> > > +??????????? led_cdev->name);
> > > +??????? device_unregister(led_cdev->dev);
> > > +??????? mutex_unlock(&led_cdev->led_access);
> > > +??????? return PTR_ERR(led_cdev->regulator);
> > 
> > This is listed as optional in the DT doc.? This appears to be required.
> 
> The regulator core will provide a dummy regulator if none is given in the
> device tree. I would rather have an error in that case, but that is not how
> it works.

If you actively wanted to get -ENODEV back when there is no regulator
then you can use devm_regulator_get_optional() for that.

However perhaps be careful what you wish for. If you use get_optional()
then you will have to sprinkle NULL or IS_ERR() checks everywhere. I'd
favour using the current approach!


Daniel.

> 
> 
> > 
> > I prefer to keep it optional.? Many LED drivers are connected to fixed
> > non-managed supplies.
> > 
> > > +??? }
> > > +
> > > ????? if (led_cdev->flags & LED_BRIGHT_HW_CHANGED) {
> > > ????????? ret = led_add_brightness_hw_changed(led_cdev);
> > > ????????? if (ret) {
> > > diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c
> > > index 7107cd7e87cf..139de6b08cad 100644
> > > --- a/drivers/leds/led-core.c
> > > +++ b/drivers/leds/led-core.c
> > > @@ -16,6 +16,7 @@
> > > ? #include <linux/rwsem.h>
> > > ? #include <linux/slab.h>
> > > ? #include "leds.h"
> > > +#include <linux/regulator/consumer.h>
> > > ? ? DECLARE_RWSEM(leds_list_lock);
> > > ? EXPORT_SYMBOL_GPL(leds_list_lock);
> > > @@ -23,6 +24,31 @@ EXPORT_SYMBOL_GPL(leds_list_lock);
> > > ? LIST_HEAD(leds_list);
> > > ? EXPORT_SYMBOL_GPL(leds_list);
> > > ? +static bool __led_need_regulator_update(struct led_classdev
> > > *led_cdev,
> > > +??????????????????? int brightness)
> > > +{
> > > +??? bool new_regulator_state = (brightness != LED_OFF);
> > > +
> > > +??? return led_cdev->regulator_state != new_regulator_state;
> > > +}
> > > +
> > > +static int __led_handle_regulator(struct led_classdev *led_cdev,
> > > +??????????????? int brightness)
> > > +{
> > > +??? if (__led_need_regulator_update(led_cdev, brightness)) {
> > > +??????? int ret;
> > 
> > Prefer to this to be moved up.
> ok
> > 
> > > +
> > > +??????? if (brightness != LED_OFF)
> > > +??????????? ret = regulator_enable(led_cdev->regulator);
> > > +??????? else
> > > +??????????? ret = regulator_disable(led_cdev->regulator);
> > > +??????? if (ret)
> > > +??????????? return ret;
> > new line
> > > +??????? led_cdev->regulator_state = (brightness != LED_OFF);
> > > +??? }
> > > +??? return 0;
> > > +}
> > > +
> > > ? static int __led_set_brightness(struct led_classdev *led_cdev,
> > > ????????????????? enum led_brightness value)
> > > ? {
> > > @@ -80,6 +106,7 @@ static void led_timer_function(struct timer_list *t)
> > > ????? }
> > > ? ????? led_set_brightness_nosleep(led_cdev, brightness);
> > > +??? __led_handle_regulator(led_cdev, brightness);
> > 
> > Again this seems to indicate that the regulator is a required property
> > for the LEDs
> > 
> > This needs to be made optional.? And the same comment through out for
> > every call.
> > 
> > 
> > > ? ????? /* Return in next iteration if led is in one-shot mode and
> > > we are in
> > > ?????? * the final blink state so that the led is toggled each
> > > delay_on +
> > > @@ -115,6 +142,8 @@ static void set_brightness_delayed(struct
> > > work_struct *ws)
> > > ????? if (ret == -ENOTSUPP)
> > > ????????? ret = __led_set_brightness_blocking(led_cdev,
> > > ????????????????????? led_cdev->delayed_set_value);
> > > +??? __led_handle_regulator(led_cdev, led_cdev->delayed_set_value);
> > > +
> > > ????? if (ret < 0 &&
> > > ????????? /* LED HW might have been unplugged, therefore don't warn */
> > > ????????? !(ret == -ENODEV && (led_cdev->flags & LED_UNREGISTERING) &&
> > > @@ -141,6 +170,7 @@ static void led_set_software_blink(struct
> > > led_classdev *led_cdev,
> > > ????? /* never on - just set to off */
> > > ????? if (!delay_on) {
> > > ????????? led_set_brightness_nosleep(led_cdev, LED_OFF);
> > > +??????? __led_handle_regulator(led_cdev, LED_OFF);
> > > ????????? return;
> > > ????? }
> > > ? @@ -148,6 +178,7 @@ static void led_set_software_blink(struct
> > > led_classdev *led_cdev,
> > > ????? if (!delay_off) {
> > > ????????? led_set_brightness_nosleep(led_cdev,
> > > ???????????????????????? led_cdev->blink_brightness);
> > > +??????? __led_handle_regulator(led_cdev, led_cdev->blink_brightness);
> > > ????????? return;
> > > ????? }
> > > ? @@ -256,8 +287,14 @@ void led_set_brightness_nopm(struct
> > > led_classdev *led_cdev,
> > > ??????????????????? enum led_brightness value)
> > > ? {
> > > ????? /* Use brightness_set op if available, it is guaranteed not to
> > > sleep */
> > > -??? if (!__led_set_brightness(led_cdev, value))
> > > -??????? return;
> > > +??? if (!__led_set_brightness(led_cdev, value)) {
> > > +??????? /*
> > > +???????? * if regulator state doesn't need to be changed, that is all/
> > > +???????? * Otherwise delegate the change to a work queue
> > > +???????? */
> > > +??????? if (!__led_need_regulator_update(led_cdev, value))
> > > +??????????? return;
> > > +??? }
> > > ? ????? /* If brightness setting can sleep, delegate it to a work
> > > queue task */
> > > ????? led_cdev->delayed_set_value = value;
> > > @@ -280,6 +317,8 @@ EXPORT_SYMBOL_GPL(led_set_brightness_nosleep);
> > > ? int led_set_brightness_sync(struct led_classdev *led_cdev,
> > > ????????????????? enum led_brightness value)
> > > ? {
> > > +??? int ret;
> > > +
> > > ????? if (led_cdev->blink_delay_on || led_cdev->blink_delay_off)
> > > ????????? return -EBUSY;
> > > ? @@ -288,7 +327,15 @@ int led_set_brightness_sync(struct
> > > led_classdev *led_cdev,
> > > ????? if (led_cdev->flags & LED_SUSPENDED)
> > > ????????? return 0;
> > > ? -??? return __led_set_brightness_blocking(led_cdev,
> > > led_cdev->brightness);
> > > +??? ret = __led_set_brightness_blocking(led_cdev,
> > > led_cdev->brightness);
> > > +??? if (ret)
> > > +??????? return ret;
> > > +
> > > +??? ret = __led_handle_regulator(led_cdev, led_cdev->brightness);
> > 
> > Can't you just return here?
> 
> ok
> 
> 
> thanks for the review
> 
> JJ
> 
> > 
> > Dan
> > 
> > > +??? if (ret)
> > > +??????? return ret;
> > > +
> > > +??? return 0;
> > > ? }
> > > ? EXPORT_SYMBOL_GPL(led_set_brightness_sync);
> > > ? diff --git a/include/linux/leds.h b/include/linux/leds.h
> > > index 9b2bf574a17a..bee8e3f8dddd 100644
> > > --- a/include/linux/leds.h
> > > +++ b/include/linux/leds.h
> > > @@ -123,6 +123,10 @@ struct led_classdev {
> > > ? ????? /* Ensures consistent access to the LED Flash Class device */
> > > ????? struct mutex??????? led_access;
> > > +
> > > +??? /* regulator */
> > > +??? struct regulator??? *regulator;
> > > +??? bool??????????? regulator_state;
> > > ? };
> > > ? ? extern int of_led_classdev_register(struct device *parent,