On Thu 2017-07-06 10:01:32, Thierry Reding wrote: > On Fri, Jun 30, 2017 at 01:21:07PM +0200, Enric Balletbo i Serra wrote: > > From: huang lin <h...@rock-chips.com> > > > > Some panels (i.e. N116BGE-L41), in their power sequence specifications, > > request a delay between set the PWM signal and enable the backlight and > > between clear the PWM signal and disable the backlight. Add support for > > the new pwm-delay-us property to meet the timing. > > > > Note that this patch inverts current sequence. Before this patch the > > enable signal was set before the PWM signal and vice-versa on power off. > > > > I assumed that this sequence was wrong, at least it is on different panel > > datasheets that I checked, so I inverted the sequence to follow: > > > > On power on, set the PWM signal, wait, and set the LED_EN signal. > > On power off, clear the LED_EN signal, wait, and stop the PWM signal. > > I think this should be two separate patches to make it easier to revert > the inverted sequence should it prove to regress on other panels.
Don't make this overly complex. This is trivial. No need to split it into more patches. > Two more comments below. > > > Signed-off-by: huang lin <h...@rock-chips.com> > > Signed-off-by: Enric Balletbo i Serra <enric.balle...@collabora.com> > > --- > > Changes since v1: > > - As suggested by Daniel Thompson > > - Do not assume power-on delay and power-off delay will be the same > > - Move the check of dt property to the parse dt function. > > > > v1: https://lkml.org/lkml/2017/6/28/219 > > > > drivers/video/backlight/pwm_bl.c | 24 ++++++++++++++++++++---- > > include/linux/pwm_backlight.h | 1 + > > 2 files changed, 21 insertions(+), 4 deletions(-) > > > > diff --git a/drivers/video/backlight/pwm_bl.c > > b/drivers/video/backlight/pwm_bl.c > > index 002f1ce..0f5470e 100644 > > --- a/drivers/video/backlight/pwm_bl.c > > +++ b/drivers/video/backlight/pwm_bl.c > > @@ -10,6 +10,7 @@ > > * published by the Free Software Foundation. > > */ > > > > +#include <linux/delay.h> > > #include <linux/gpio/consumer.h> > > #include <linux/gpio.h> > > #include <linux/module.h> > > @@ -35,6 +36,7 @@ struct pwm_bl_data { > > struct gpio_desc *enable_gpio; > > unsigned int scale; > > bool legacy; > > + unsigned int pwm_delay[2]; > > int (*notify)(struct device *, > > int brightness); > > void (*notify_after)(struct device *, > > @@ -54,10 +56,14 @@ static void pwm_backlight_power_on(struct pwm_bl_data > > *pb, int brightness) > > if (err < 0) > > dev_err(pb->dev, "failed to enable power supply\n"); > > > > + pwm_enable(pb->pwm); > > + > > + if (pb->pwm_delay[0]) > > + usleep_range(pb->pwm_delay[0], pb->pwm_delay[0] + 2000); > > 2000 us is kind of arbitrary. What if pwm_delay[0] is on the order of 20 > us? Making the delay 2 ms longer (in the worst case) seems somewhat > excessive. Why not something like: > > usleep_range(pb->pwm_delay[0], pb->pwm_delay[0] * 2); > > ? > > > + > > if (pb->enable_gpio) > > gpiod_set_value_cansleep(pb->enable_gpio, 1); > > > > - pwm_enable(pb->pwm); > > pb->enabled = true; > > } > > > > @@ -66,12 +72,15 @@ static void pwm_backlight_power_off(struct pwm_bl_data > > *pb) > > if (!pb->enabled) > > return; > > > > - pwm_config(pb->pwm, 0, pb->period); > > - pwm_disable(pb->pwm); > > - > > if (pb->enable_gpio) > > gpiod_set_value_cansleep(pb->enable_gpio, 0); > > > > + if (pb->pwm_delay[1]) > > + usleep_range(pb->pwm_delay[1], pb->pwm_delay[1] + 2000); > > + > > + pwm_config(pb->pwm, 0, pb->period); > > + pwm_disable(pb->pwm); > > + > > regulator_disable(pb->power_supply); > > pb->enabled = false; > > } > > @@ -174,6 +183,12 @@ static int pwm_backlight_parse_dt(struct device *dev, > > data->max_brightness--; > > } > > > > + /* read pwm to enable pre/post delays from DT property */ > > This comment is confusing. This isn't reading anything from the PWM. > > Thierry -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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