From: Lakshmi Sowjanya D <lakshmi.sowjanya.d@xxxxxxxxx> The Intel(R) PMC Timed I/O driver uses the PWM interface to export a clock from the platform. Normally, PWM output is not phase aligned to any clock. To remedy this: add an additional PWM state parameter specifying alignment in nanoseconds within the output period. Co-developed-by: Christopher Hall <christopher.s.hall@xxxxxxxxx> Signed-off-by: Christopher Hall <christopher.s.hall@xxxxxxxxx> Signed-off-by: Tamal Saha <tamal.saha@xxxxxxxxx> Signed-off-by: Lakshmi Sowjanya D <lakshmi.sowjanya.d@xxxxxxxxx> Reviewed-by: Mark Gross <mgross@xxxxxxxxxxxxxxx> --- drivers/pwm/core.c | 7 +++++-- drivers/pwm/sysfs.c | 37 +++++++++++++++++++++++++++++++++++++ include/linux/pwm.h | 2 ++ 3 files changed, 44 insertions(+), 2 deletions(-) diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c index c658585ac3bc..5d6c64916e51 100644 --- a/drivers/pwm/core.c +++ b/drivers/pwm/core.c @@ -271,6 +271,7 @@ int pwmchip_add(struct pwm_chip *chip) pwm->chip = chip; pwm->pwm = chip->base + i; pwm->hwpwm = i; + pwm->state.alignment = 0; radix_tree_insert(&pwm_tree, pwm->pwm, pwm); } @@ -535,7 +536,8 @@ int pwm_apply_state(struct pwm_device *pwm, const struct pwm_state *state) int err; if (!pwm || !state || !state->period || - state->duty_cycle > state->period) + state->duty_cycle > state->period || + state->alignment >= state->period) return -EINVAL; chip = pwm->chip; @@ -544,7 +546,8 @@ int pwm_apply_state(struct pwm_device *pwm, const struct pwm_state *state) state->duty_cycle == pwm->state.duty_cycle && state->polarity == pwm->state.polarity && state->enabled == pwm->state.enabled && - state->usage_power == pwm->state.usage_power) + state->usage_power == pwm->state.usage_power && + state->alignment == pwm->state.alignment) return 0; if (chip->ops->apply) { diff --git a/drivers/pwm/sysfs.c b/drivers/pwm/sysfs.c index 9903c3a7eced..5d020618d8ba 100644 --- a/drivers/pwm/sysfs.c +++ b/drivers/pwm/sysfs.c @@ -33,6 +33,41 @@ static struct pwm_device *child_to_pwm_device(struct device *child) return export->pwm; } +static ssize_t alignment_show(struct device *child, + struct device_attribute *attr, + char *buf) +{ + const struct pwm_device *pwm = child_to_pwm_device(child); + struct pwm_state state; + + pwm_get_state(pwm, &state); + + return sprintf(buf, "%llu\n", state.alignment); +} + +static ssize_t alignment_store(struct device *child, + struct device_attribute *attr, + const char *buf, size_t size) +{ + struct pwm_export *export = child_to_pwm_export(child); + struct pwm_device *pwm = export->pwm; + struct pwm_state state; + unsigned int val; + int ret; + + ret = kstrtouint(buf, 0, &val); + if (ret) + return ret; + + mutex_lock(&export->lock); + pwm_get_state(pwm, &state); + state.alignment = val; + ret = pwm_apply_state(pwm, &state); + mutex_unlock(&export->lock); + + return ret ? : size; +} + static ssize_t period_show(struct device *child, struct device_attribute *attr, char *buf) @@ -219,6 +254,7 @@ static DEVICE_ATTR_RW(period); static DEVICE_ATTR_RW(duty_cycle); static DEVICE_ATTR_RW(enable); static DEVICE_ATTR_RW(polarity); +static DEVICE_ATTR_RW(alignment); static DEVICE_ATTR_RO(capture); static struct attribute *pwm_attrs[] = { @@ -226,6 +262,7 @@ static struct attribute *pwm_attrs[] = { &dev_attr_duty_cycle.attr, &dev_attr_enable.attr, &dev_attr_polarity.attr, + &dev_attr_alignment.attr, &dev_attr_capture.attr, NULL }; diff --git a/include/linux/pwm.h b/include/linux/pwm.h index d805fee81e2c..17ca1ea7ba94 100644 --- a/include/linux/pwm.h +++ b/include/linux/pwm.h @@ -59,6 +59,7 @@ enum { * output but has more freedom regarding signal form. * If supported, the signal can be optimized, for example to * improve EMI by phase shifting individual channels. + * @alignment: offset in ns to device clock second */ struct pwm_state { u64 period; @@ -66,6 +67,7 @@ struct pwm_state { enum pwm_polarity polarity; bool enabled; bool usage_power; + u64 alignment; }; /** -- 2.17.1