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video: backlight: Support PWMs without a known period_ns

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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.

Also adds a sandbox test for a PWM channel that has a fixed period,
checking that the resulting duty_cycle matches on a set_config() even if
the requested period_ns can't be set.

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
This commit is contained in:
Alper Nebi Yasak 2020-10-22 23:49:26 +03:00 committed by Anatolij Gustschin
parent 9749d2ea29
commit fefa713b18
4 changed files with 42 additions and 8 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

11
drivers/pwm/sandbox_pwm.c
View file

@ -59,8 +59,15 @@ static int sandbox_pwm_set_config(struct udevice *dev, uint channel,
if (channel >= NUM_CHANNELS)
return -ENOSPC;
chan = &priv->chan[channel];
chan->period_ns = period_ns;
chan->duty_ns = duty_ns;
if (channel == 2) {
/* Pretend to have some fixed period */
chan->period_ns = 4096;
chan->duty_ns = duty_ns * 4096 / period_ns;
} else {
chan->period_ns = period_ns;
chan->duty_ns = duty_ns;
}
return 0;
}

20
drivers/video/pwm_backlight.c
View file

@ -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);
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);
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,
priv->cur_level - priv->min_level);
}
if (ret)
return log_ret(ret);
@ -213,10 +220,11 @@ static int pwm_backlight_of_to_plat(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];

8
include/pwm.h
View file

@ -17,6 +17,10 @@ struct pwm_ops {
/**
* set_config() - Set the PWM configuration
*
* Change both the PWM device's period and it's duty period if
* possible. Otherwise, set an appropriate duty period that best
* matches the given period_ns / duty_ns ratio for the device.
*
* @dev: PWM device to update
* @channel: PWM channel to update
* @period_ns: PWM period in nanoseconds
@ -51,6 +55,10 @@ struct pwm_ops {
/**
* pwm_set_config() - Set the PWM configuration
*
* Change both the PWM device's period and it's duty period if
* possible. Otherwise, set an appropriate duty period that best
* matches the given period_ns / duty_ns ratio for the device.
*
* @dev: PWM device to update
* @channel: PWM channel to update
* @period_ns: PWM period in nanoseconds

11
test/dm/pwm.c
View file

@ -6,6 +6,7 @@
#include <common.h>
#include <dm.h>
#include <pwm.h>
#include <asm/test.h>
#include <dm/test.h>
#include <test/test.h>
#include <test/ut.h>
@ -14,6 +15,10 @@
static int dm_test_pwm_base(struct unit_test_state *uts)
{
struct udevice *dev;
uint period_ns;
uint duty_ns;
bool enable;
bool polarity;
ut_assertok(uclass_get_device(UCLASS_PWM, 0, &dev));
ut_assertnonnull(dev);
@ -24,6 +29,12 @@ static int dm_test_pwm_base(struct unit_test_state *uts)
ut_asserteq(-ENOSPC, pwm_set_enable(dev, 3, true));
ut_assertok(pwm_set_invert(dev, 0, true));
ut_assertok(pwm_set_config(dev, 2, 100, 50));
ut_assertok(sandbox_pwm_get_config(dev, 2, &period_ns, &duty_ns,
&enable, &polarity));
ut_asserteq(period_ns, 4096);
ut_asserteq(duty_ns, 50 * 4096 / 100);
ut_assertok(uclass_get_device(UCLASS_PWM, 1, &dev));
ut_asserteq(-ENODEV, uclass_get_device(UCLASS_PWM, 2, &dev));