diff options
| -rw-r--r-- | drivers/pwm/Kconfig | 9 | ||||
| -rw-r--r-- | drivers/pwm/core.c | 135 | ||||
| -rw-r--r-- | include/linux/pwm.h | 4 |
3 files changed, 140 insertions, 8 deletions
diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig index 30190beeb6e9..e21834f44a29 100644 --- a/drivers/pwm/Kconfig +++ b/drivers/pwm/Kconfig @@ -33,6 +33,15 @@ config PWM_SYSFS bool default y if SYSFS +config PWM_DEBUG + bool "PWM lowlevel drivers additional checks and debug messages" + depends on DEBUG_KERNEL + help + This option enables some additional checks to help lowlevel driver + authors to get their callbacks implemented correctly. + It is expected to introduce some runtime overhead and diagnostic + output to the kernel log, so only enable while working on a driver. + config PWM_AB8500 tristate "AB8500 PWM support" depends on AB8500_CORE && ARCH_U8500 diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c index 5a7f6598c05f..e9b9283cff28 100644 --- a/drivers/pwm/core.c +++ b/drivers/pwm/core.c @@ -120,6 +120,9 @@ static int pwm_device_request(struct pwm_device *pwm, const char *label) if (pwm->chip->ops->get_state) { pwm->chip->ops->get_state(pwm->chip, pwm, &pwm->state); trace_pwm_get(pwm, &pwm->state); + + if (IS_ENABLED(PWM_DEBUG)) + pwm->last = pwm->state; } set_bit(PWMF_REQUESTED, &pwm->flags); @@ -232,17 +235,28 @@ void *pwm_get_chip_data(struct pwm_device *pwm) } EXPORT_SYMBOL_GPL(pwm_get_chip_data); -static bool pwm_ops_check(const struct pwm_ops *ops) +static bool pwm_ops_check(const struct pwm_chip *chip) { + + const struct pwm_ops *ops = chip->ops; + /* driver supports legacy, non-atomic operation */ - if (ops->config && ops->enable && ops->disable) - return true; + if (ops->config && ops->enable && ops->disable) { + if (IS_ENABLED(CONFIG_PWM_DEBUG)) + dev_warn(chip->dev, + "Driver needs updating to atomic API\n"); - /* driver supports atomic operation */ - if (ops->apply) return true; + } - return false; + if (!ops->apply) + return false; + + if (IS_ENABLED(CONFIG_PWM_DEBUG) && !ops->get_state) + dev_warn(chip->dev, + "Please implement the .get_state() callback\n"); + + return true; } /** @@ -266,7 +280,7 @@ int pwmchip_add_with_polarity(struct pwm_chip *chip, if (!chip || !chip->dev || !chip->ops || !chip->npwm) return -EINVAL; - if (!pwm_ops_check(chip->ops)) + if (!pwm_ops_check(chip)) return -EINVAL; mutex_lock(&pwm_lock); @@ -450,6 +464,107 @@ void pwm_free(struct pwm_device *pwm) } EXPORT_SYMBOL_GPL(pwm_free); +void pwm_apply_state_debug(struct pwm_device *pwm, + const struct pwm_state *state) +{ + struct pwm_state *last = &pwm->last; + struct pwm_chip *chip = pwm->chip; + struct pwm_state s1, s2; + int err; + + if (!IS_ENABLED(CONFIG_PWM_DEBUG)) + return; + + /* No reasonable diagnosis possible without .get_state() */ + if (!chip->ops->get_state) + return; + + /* + * *state was just applied. Read out the hardware state and do some + * checks. + */ + + chip->ops->get_state(chip, pwm, &s1); + trace_pwm_get(pwm, &s1); + + /* + * The lowlevel driver either ignored .polarity (which is a bug) or as + * best effort inverted .polarity and fixed .duty_cycle respectively. + * Undo this inversion and fixup for further tests. + */ + if (s1.enabled && s1.polarity != state->polarity) { + s2.polarity = state->polarity; + s2.duty_cycle = s1.period - s1.duty_cycle; + s2.period = s1.period; + s2.enabled = s1.enabled; + } else { + s2 = s1; + } + + if (s2.polarity != state->polarity && + state->duty_cycle < state->period) + dev_warn(chip->dev, ".apply ignored .polarity\n"); + + if (state->enabled && + last->polarity == state->polarity && + last->period > s2.period && + last->period <= state->period) + dev_warn(chip->dev, + ".apply didn't pick the best available period (requested: %u, applied: %u, possible: %u)\n", + state->period, s2.period, last->period); + + if (state->enabled && state->period < s2.period) + dev_warn(chip->dev, + ".apply is supposed to round down period (requested: %u, applied: %u)\n", + state->period, s2.period); + + if (state->enabled && + last->polarity == state->polarity && + last->period == s2.period && + last->duty_cycle > s2.duty_cycle && + last->duty_cycle <= state->duty_cycle) + dev_warn(chip->dev, + ".apply didn't pick the best available duty cycle (requested: %u/%u, applied: %u/%u, possible: %u/%u)\n", + state->duty_cycle, state->period, + s2.duty_cycle, s2.period, + last->duty_cycle, last->period); + + if (state->enabled && state->duty_cycle < s2.duty_cycle) + dev_warn(chip->dev, + ".apply is supposed to round down duty_cycle (requested: %u/%u, applied: %u/%u)\n", + state->duty_cycle, state->period, + s2.duty_cycle, s2.period); + + if (!state->enabled && s2.enabled && s2.duty_cycle > 0) + dev_warn(chip->dev, + "requested disabled, but yielded enabled with duty > 0"); + + /* reapply the state that the driver reported being configured. */ + err = chip->ops->apply(chip, pwm, &s1); + if (err) { + *last = s1; + dev_err(chip->dev, "failed to reapply current setting\n"); + return; + } + + trace_pwm_apply(pwm, &s1); + + chip->ops->get_state(chip, pwm, last); + trace_pwm_get(pwm, last); + + /* reapplication of the current state should give an exact match */ + if (s1.enabled != last->enabled || + s1.polarity != last->polarity || + (s1.enabled && s1.period != last->period) || + (s1.enabled && s1.duty_cycle != last->duty_cycle)) { + dev_err(chip->dev, + ".apply is not idempotent (ena=%d pol=%d %u/%u) -> (ena=%d pol=%d %u/%u)\n", + s1.enabled, s1.polarity, s1.duty_cycle, s1.period, + last->enabled, last->polarity, last->duty_cycle, + last->period); + } +} + /** * pwm_apply_state() - atomically apply a new state to a PWM device * @pwm: PWM device @@ -480,6 +595,12 @@ int pwm_apply_state(struct pwm_device *pwm, const struct pwm_state *state) trace_pwm_apply(pwm, state); pwm->state = *state; + + /* + * only do this after pwm->state was applied as some + * implementations of .get_state depend on this + */ + pwm_apply_state_debug(pwm, state); } else { /* * FIXME: restore the initial state in case of error. diff --git a/include/linux/pwm.h b/include/linux/pwm.h index 0ef808d925bb..2635b2a55090 100644 --- a/include/linux/pwm.h +++ b/include/linux/pwm.h @@ -71,7 +71,8 @@ struct pwm_state { * @chip: PWM chip providing this PWM device * @chip_data: chip-private data associated with the PWM device * @args: PWM arguments - * @state: curent PWM channel state + * @state: last applied state + * @last: last implemented state (for PWM_DEBUG) */ struct pwm_device { const char *label; @@ -83,6 +84,7 @@ struct pwm_device { struct pwm_args args; struct pwm_state state; + struct pwm_state last; }; /** |