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. 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
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