| Message ID | 20200923165231.18188-1-alpernebiyasak@gmail.com |
|---|---|
| State | Superseded |
| Delegated to: | Anatolij Gustschin |
| Headers | show |
| Series | [1/2] video: backlight: Support PWMs without a known period_ns | expand |
Hi Alper, On Wed, 23 Sep 2020 at 10:52, Alper Nebi Yasak <alpernebiyasak@gmail.com> wrote: > > The PWM device provided by Chrome OS EC doesn't really support anything > other than setting a relative duty cycle. To support it as a backlight, > this patch makes the PWM period optional in the device tree and pretends > the valid brightness range is its period_ns. > > Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com> > --- > > drivers/video/pwm_backlight.c | 20 ++++++++++++++------ > 1 file changed, 14 insertions(+), 6 deletions(-) This looks OK. But please update the comment for pwm_set_config() to describe the param updates and add a sandbox test to pwm.c Does this affect the devicetree binding? Regards, Simon
On 24/09/2020 19:08, Simon Glass wrote: > Hi Alper, > > On Wed, 23 Sep 2020 at 10:52, Alper Nebi Yasak <alpernebiyasak@gmail.com> wrote: >> >> The PWM device provided by Chrome OS EC doesn't really support anything >> other than setting a relative duty cycle. To support it as a backlight, >> this patch makes the PWM period optional in the device tree and pretends >> the valid brightness range is its period_ns. >> >> Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com> >> --- >> >> drivers/video/pwm_backlight.c | 20 ++++++++++++++------ >> 1 file changed, 14 insertions(+), 6 deletions(-) > > This looks OK. > > But please update the comment for pwm_set_config() to describe the > param updates and add a sandbox test to pwm.c OK. I'm also adding the same comment to pwm_ops->set_config() as it has the same change in its meaning. > Does this affect the devicetree binding? I don't think it does, or more precisely I'm making the backlight driver support the following where I think the bindings themselves were already valid: pwm: pwm { #pwm-cells = <1>; [...] }; backlight: backlight { compatible = "pwm-backlight"; pwms = <&pwm 0>; [...] }; (These with &cros-ec-pwm already exist in rk3399-gru-bob.dts and rk3399-gru-kevin.dts)
diff --git a/drivers/video/pwm_backlight.c b/drivers/video/pwm_backlight.c index 468a5703bd..4c2a307462 100644 --- a/drivers/video/pwm_backlight.c +++ b/drivers/video/pwm_backlight.c @@ -62,10 +62,17 @@ static int set_pwm(struct pwm_backlight_priv *priv) uint duty_cycle; int ret; - duty_cycle = priv->period_ns * (priv->cur_level - priv->min_level) / - (priv->max_level - priv->min_level + 1); - ret = pwm_set_config(priv->pwm, priv->channel, priv->period_ns, - duty_cycle); + if (priv->period_ns) { + duty_cycle = priv->period_ns * (priv->cur_level - priv->min_level) / + (priv->max_level - priv->min_level + 1); + ret = pwm_set_config(priv->pwm, priv->channel, priv->period_ns, + duty_cycle); + } else { + /* PWM driver will internally scale these like the above. */ + ret = pwm_set_config(priv->pwm, priv->channel, + priv->max_level - priv->min_level + 1, + priv->cur_level - priv->min_level); + } if (ret) return log_ret(ret); @@ -213,10 +220,11 @@ static int pwm_backlight_ofdata_to_platdata(struct udevice *dev) log_debug("Cannot get PWM: ret=%d\n", ret); return log_ret(ret); } - if (args.args_count < 2) + if (args.args_count < 1) return log_msg_ret("Not enough arguments to pwm\n", -EINVAL); priv->channel = args.args[0]; - priv->period_ns = args.args[1]; + if (args.args_count > 1) + priv->period_ns = args.args[1]; if (args.args_count > 2) priv->polarity = args.args[2];
The PWM device provided by Chrome OS EC doesn't really support anything other than setting a relative duty cycle. To support it as a backlight, this patch makes the PWM period optional in the device tree and pretends the valid brightness range is its period_ns. Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com> --- drivers/video/pwm_backlight.c | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 deletions(-)