diff options
Diffstat (limited to 'drivers/pwm/core.c')
| -rw-r--r-- | drivers/pwm/core.c | 118 |
1 files changed, 86 insertions, 32 deletions
diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c index 0387bd838487..4d842c692194 100644 --- a/drivers/pwm/core.c +++ b/drivers/pwm/core.c @@ -216,21 +216,28 @@ static int __pwm_write_waveform(struct pwm_chip *chip, struct pwm_device *pwm, c * * Typically a given waveform cannot be implemented exactly by hardware, e.g. * because hardware only supports coarse period resolution or no duty_offset. - * This function returns the actually implemented waveform if you pass wf to - * pwm_set_waveform_might_sleep now. + * This function returns the actually implemented waveform if you pass @wf to + * pwm_set_waveform_might_sleep() now. * * Note however that the world doesn't stop turning when you call it, so when - * doing + * doing:: * - * pwm_round_waveform_might_sleep(mypwm, &wf); - * pwm_set_waveform_might_sleep(mypwm, &wf, true); + * pwm_round_waveform_might_sleep(mypwm, &wf); + * pwm_set_waveform_might_sleep(mypwm, &wf, true); * * the latter might fail, e.g. because an input clock changed its rate between * these two calls and the waveform determined by * pwm_round_waveform_might_sleep() cannot be implemented any more. * - * Returns 0 on success, 1 if there is no valid hardware configuration matching - * the input waveform under the PWM rounding rules or a negative errno. + * Usually all values passed in @wf are rounded down to the nearest possible + * value (in the order period_length_ns, duty_length_ns and then + * duty_offset_ns). Only if this isn't possible, a value might grow. See the + * documentation for pwm_set_waveform_might_sleep() for a more formal + * description. + * + * Returns: 0 on success, 1 if at least one value had to be rounded up or a + * negative errno. + * Context: May sleep. */ int pwm_round_waveform_might_sleep(struct pwm_device *pwm, struct pwm_waveform *wf) { @@ -270,10 +277,10 @@ int pwm_round_waveform_might_sleep(struct pwm_device *pwm, struct pwm_waveform * wf_req.duty_length_ns, wf_req.period_length_ns, wf_req.duty_offset_ns, ret_tohw); if (IS_ENABLED(CONFIG_PWM_DEBUG) && - ret_tohw == 0 && !pwm_check_rounding(&wf_req, wf)) - dev_err(&chip->dev, "Wrong rounding: requested %llu/%llu [+%llu], result %llu/%llu [+%llu]\n", + (ret_tohw == 0) != pwm_check_rounding(&wf_req, wf)) + dev_err(&chip->dev, "Wrong rounding: requested %llu/%llu [+%llu], result %llu/%llu [+%llu], ret: %d\n", wf_req.duty_length_ns, wf_req.period_length_ns, wf_req.duty_offset_ns, - wf->duty_length_ns, wf->period_length_ns, wf->duty_offset_ns); + wf->duty_length_ns, wf->period_length_ns, wf->duty_offset_ns, ret_tohw); return ret_tohw; } @@ -287,6 +294,9 @@ EXPORT_SYMBOL_GPL(pwm_round_waveform_might_sleep); * * Stores the current configuration of the PWM in @wf. Note this is the * equivalent of pwm_get_state_hw() (and not pwm_get_state()) for pwm_waveform. + * + * Returns: 0 on success or a negative errno + * Context: May sleep. */ int pwm_get_waveform_might_sleep(struct pwm_device *pwm, struct pwm_waveform *wf) { @@ -341,10 +351,10 @@ static int __pwm_set_waveform(struct pwm_device *pwm, if (err) return err; - if (IS_ENABLED(CONFIG_PWM_DEBUG) && ret_tohw == 0 && !pwm_check_rounding(wf, &wf_rounded)) - dev_err(&chip->dev, "Wrong rounding: requested %llu/%llu [+%llu], result %llu/%llu [+%llu]\n", + if (IS_ENABLED(CONFIG_PWM_DEBUG) && (ret_tohw == 0) != pwm_check_rounding(wf, &wf_rounded)) + dev_err(&chip->dev, "Wrong rounding: requested %llu/%llu [+%llu], result %llu/%llu [+%llu], ret: %d\n", wf->duty_length_ns, wf->period_length_ns, wf->duty_offset_ns, - wf_rounded.duty_length_ns, wf_rounded.period_length_ns, wf_rounded.duty_offset_ns); + wf_rounded.duty_length_ns, wf_rounded.period_length_ns, wf_rounded.duty_offset_ns, ret_tohw); if (exact && pwmwfcmp(wf, &wf_rounded)) { dev_dbg(&chip->dev, "Requested no rounding, but %llu/%llu [+%llu] -> %llu/%llu [+%llu]\n", @@ -395,13 +405,37 @@ static int __pwm_set_waveform(struct pwm_device *pwm, * * Typically a requested waveform cannot be implemented exactly, e.g. because * you requested .period_length_ns = 100 ns, but the hardware can only set - * periods that are a multiple of 8.5 ns. With that hardware passing exact = - * true results in pwm_set_waveform_might_sleep() failing and returning 1. If - * exact = false you get a period of 93.5 ns (i.e. the biggest period not bigger - * than the requested value). - * Note that even with exact = true, some rounding by less than 1 is + * periods that are a multiple of 8.5 ns. With that hardware passing @exact = + * true results in pwm_set_waveform_might_sleep() failing and returning -EDOM. + * If @exact = false you get a period of 93.5 ns (i.e. the biggest period not + * bigger than the requested value). + * Note that even with @exact = true, some rounding by less than 1 ns is * possible/needed. In the above example requesting .period_length_ns = 94 and - * exact = true, you get the hardware configured with period = 93.5 ns. + * @exact = true, you get the hardware configured with period = 93.5 ns. + * + * Let C be the set of possible hardware configurations for a given PWM device, + * consisting of tuples (p, d, o) where p is the period length, d is the duty + * length and o the duty offset. + * + * The following algorithm is implemented to pick the hardware setting + * (p, d, o) ∈ C for a given request (p', d', o') with @exact = false:: + * + * p = max( { ṗ | ∃ ḋ, ȯ : (ṗ, ḋ, ȯ) ∈ C ∧ ṗ ≤ p' } ∪ { min({ ṗ | ∃ ḋ, ȯ : (ṗ, ḋ, ȯ) ∈ C }) }) + * d = max( { ḋ | ∃ ȯ : (p, ḋ, ȯ) ∈ C ∧ ḋ ≤ d' } ∪ { min({ ḋ | ∃ ȯ : (p, ḋ, ȯ) ∈ C }) }) + * o = max( { ȯ | (p, d, ȯ) ∈ C ∧ ȯ ≤ o' } ∪ { min({ ȯ | (p, d, ȯ) ∈ C }) }) + * + * In words: The chosen period length is the maximal possible period length not + * bigger than the requested period length and if that doesn't exist, the + * minimal period length. The chosen duty length is the maximal possible duty + * length that is compatible with the chosen period length and isn't bigger than + * the requested duty length. Again if such a value doesn't exist, the minimal + * duty length compatible with the chosen period is picked. After that the duty + * offset compatible with the chosen period and duty length is chosen in the + * same way. + * + * Returns: 0 on success, -EDOM if setting failed due to the exact waveform not + * being possible (if @exact), or a different negative errno on failure. + * Context: May sleep. */ int pwm_set_waveform_might_sleep(struct pwm_device *pwm, const struct pwm_waveform *wf, bool exact) @@ -428,6 +462,19 @@ int pwm_set_waveform_might_sleep(struct pwm_device *pwm, err = __pwm_set_waveform(pwm, wf, exact); } + /* + * map err == 1 to -EDOM for exact requests and 0 for !exact ones. Also + * make sure that -EDOM is only returned in exactly that case. Note that + * __pwm_set_waveform() should never return -EDOM which justifies the + * unlikely(). + */ + if (unlikely(err == -EDOM)) + err = -EINVAL; + else if (exact && err == 1) + err = -EDOM; + else if (err == 1) + err = 0; + return err; } EXPORT_SYMBOL_GPL(pwm_set_waveform_might_sleep); @@ -561,11 +608,6 @@ static bool pwm_state_valid(const struct pwm_state *state) return true; } -/** - * __pwm_apply() - atomically apply a new state to a PWM device - * @pwm: PWM device - * @state: new state to apply - */ static int __pwm_apply(struct pwm_device *pwm, const struct pwm_state *state) { struct pwm_chip *chip; @@ -674,6 +716,9 @@ static int __pwm_apply(struct pwm_device *pwm, const struct pwm_state *state) * Cannot be used in atomic context. * @pwm: PWM device * @state: new state to apply + * + * Returns: 0 on success, or a negative errno + * Context: May sleep. */ int pwm_apply_might_sleep(struct pwm_device *pwm, const struct pwm_state *state) { @@ -715,6 +760,9 @@ EXPORT_SYMBOL_GPL(pwm_apply_might_sleep); * Not all PWM devices support this function, check with pwm_might_sleep(). * @pwm: PWM device * @state: new state to apply + * + * Returns: 0 on success, or a negative errno + * Context: Any */ int pwm_apply_atomic(struct pwm_device *pwm, const struct pwm_state *state) { @@ -788,6 +836,9 @@ EXPORT_SYMBOL_GPL(pwm_get_state_hw); * This function will adjust the PWM config to the PWM arguments provided * by the DT or PWM lookup table. This is particularly useful to adapt * the bootloader config to the Linux one. + * + * Returns: 0 on success or a negative error code on failure. + * Context: May sleep. */ int pwm_adjust_config(struct pwm_device *pwm) { @@ -2221,25 +2272,28 @@ static void pwm_dbg_show(struct pwm_chip *chip, struct seq_file *s) for (i = 0; i < chip->npwm; i++) { struct pwm_device *pwm = &chip->pwms[i]; - struct pwm_state state; + struct pwm_state state, hwstate; pwm_get_state(pwm, &state); + pwm_get_state_hw(pwm, &hwstate); seq_printf(s, " pwm-%-3d (%-20.20s):", i, pwm->label); if (test_bit(PWMF_REQUESTED, &pwm->flags)) seq_puts(s, " requested"); - if (state.enabled) - seq_puts(s, " enabled"); + seq_puts(s, "\n"); - seq_printf(s, " period: %llu ns", state.period); - seq_printf(s, " duty: %llu ns", state.duty_cycle); - seq_printf(s, " polarity: %s", + seq_printf(s, " requested configuration: %3sabled, %llu/%llu ns, %s polarity", + state.enabled ? "en" : "dis", state.duty_cycle, state.period, state.polarity ? "inverse" : "normal"); - if (state.usage_power) - seq_puts(s, " usage_power"); + seq_puts(s, ", usage_power"); + seq_puts(s, "\n"); + + seq_printf(s, " actual configuration: %3sabled, %llu/%llu ns, %s polarity", + hwstate.enabled ? "en" : "dis", hwstate.duty_cycle, hwstate.period, + hwstate.polarity ? "inverse" : "normal"); seq_puts(s, "\n"); } |