diff options
| -rw-r--r-- | drivers/pwm/pwm-jz4740.c | 44 |
1 files changed, 29 insertions, 15 deletions
diff --git a/drivers/pwm/pwm-jz4740.c b/drivers/pwm/pwm-jz4740.c index 2eb31f2c7717..f4c6c69d0bf6 100644 --- a/drivers/pwm/pwm-jz4740.c +++ b/drivers/pwm/pwm-jz4740.c @@ -112,28 +112,42 @@ static int jz4740_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm, const struct pwm_state *state) { struct jz4740_pwm_chip *jz4740 = to_jz4740(pwm->chip); - struct clk *clk = pwm_get_chip_data(pwm), - *parent_clk = clk_get_parent(clk); - unsigned long rate, period, duty; - unsigned long long tmp; - unsigned int prescaler = 0; + unsigned long long tmp = 0xffffull * NSEC_PER_SEC; + struct clk *clk = pwm_get_chip_data(pwm); + unsigned long period, duty; uint16_t ctrl; + long rate; int err; - rate = clk_get_rate(parent_clk); - tmp = (unsigned long long)rate * state->period; - do_div(tmp, 1000000000); - period = tmp; + /* + * Limit the clock to a maximum rate that still gives us a period value + * which fits in 16 bits. + */ + do_div(tmp, state->period); - while (period > 0xffff && prescaler < 6) { - period >>= 2; - rate >>= 2; - ++prescaler; + /* + * /!\ IMPORTANT NOTE: + * ------------------- + * This code relies on the fact that clk_round_rate() will always round + * down, which is not a valid assumption given by the clk API, but only + * happens to be true with the clk drivers used for Ingenic SoCs. + * + * Right now, there is no alternative as the clk API does not have a + * round-down function (and won't have one for a while), but if it ever + * comes to light, a round-down function should be used instead. + */ + rate = clk_round_rate(clk, tmp); + if (rate < 0) { + dev_err(chip->dev, "Unable to round rate: %ld", rate); + return rate; } - if (prescaler == 6) - return -EINVAL; + /* Calculate period value */ + tmp = (unsigned long long)rate * state->period; + do_div(tmp, NSEC_PER_SEC); + period = (unsigned long)tmp; + /* Calculate duty value */ tmp = (unsigned long long)period * state->duty_cycle; do_div(tmp, state->period); duty = period - tmp; |