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 ---
Changes in v3: - Add tag: "Reviewed-by: Simon Glass sjg@chromium.org" - Adjust to match recently merged duty cycle calculation fix.
v2: https://patchwork.ozlabs.org/project/uboot/patch/20200926200851.4388-1-alper...
Changes in v2: - Add sandbox test to pwm.c (using sandbox_pwm's channel 2) - Add comments to pwm_set_config() and pwm_ops->set_config()
v1: https://patchwork.ozlabs.org/project/uboot/patch/20200923165231.18188-1-alpe...
drivers/pwm/sandbox_pwm.c | 11 +++++++++-- drivers/video/pwm_backlight.c | 20 ++++++++++++++------ include/pwm.h | 8 ++++++++ test/dm/pwm.c | 11 +++++++++++ 4 files changed, 42 insertions(+), 8 deletions(-)
diff --git a/drivers/pwm/sandbox_pwm.c b/drivers/pwm/sandbox_pwm.c index 28988187e039..3fd2e78c909d 100644 --- a/drivers/pwm/sandbox_pwm.c +++ b/drivers/pwm/sandbox_pwm.c @@ -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; } diff --git a/drivers/video/pwm_backlight.c b/drivers/video/pwm_backlight.c index 9519180ceb39..18b7a00b033c 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); - 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_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];
diff --git a/include/pwm.h b/include/pwm.h index 54ae3e64c310..97bda0856e6c 100644 --- a/include/pwm.h +++ b/include/pwm.h @@ -15,6 +15,10 @@ 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 @@ -49,6 +53,10 @@ 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 diff --git a/test/dm/pwm.c b/test/dm/pwm.c index 0de6dba1ba64..b624cf3d6558 100644 --- a/test/dm/pwm.c +++ b/test/dm/pwm.c @@ -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));