[PATCH 1/2] video: backlight: Support PWMs without a known period_ns
Alper Nebi Yasak
alpernebiyasak at gmail.com
Wed Sep 23 18:52:30 CEST 2020
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 at gmail.com>
---
drivers/video/pwm_backlight.c | 20 ++++++++++++++------
1 file changed, 14 insertions(+), 6 deletions(-)
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];
--
2.28.0
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