diff options
| -rw-r--r-- | drivers/pwm/pwm-stm32.c | 23 |
1 files changed, 16 insertions, 7 deletions
diff --git a/drivers/pwm/pwm-stm32.c b/drivers/pwm/pwm-stm32.c index a2f231d13a9f..8bae3fd2b330 100644 --- a/drivers/pwm/pwm-stm32.c +++ b/drivers/pwm/pwm-stm32.c @@ -321,22 +321,30 @@ static int stm32_pwm_config(struct stm32_pwm *priv, unsigned int ch, * First we need to find the minimal value for prescaler such that * * period_ns * clkrate - * ------------------------------ + * ------------------------------ < max_arr + 1 * NSEC_PER_SEC * (prescaler + 1) * - * isn't bigger than max_arr. + * This equation is equivalent to + * + * period_ns * clkrate + * ---------------------------- < prescaler + 1 + * NSEC_PER_SEC * (max_arr + 1) + * + * Using integer division and knowing that the right hand side is + * integer, this is further equivalent to + * + * (period_ns * clkrate) // (NSEC_PER_SEC * (max_arr + 1)) ≤ prescaler */ prescaler = mul_u64_u64_div_u64(period_ns, clk_get_rate(priv->clk), - (u64)NSEC_PER_SEC * priv->max_arr); - if (prescaler > 0) - prescaler -= 1; - + (u64)NSEC_PER_SEC * ((u64)priv->max_arr + 1)); if (prescaler > MAX_TIM_PSC) return -EINVAL; prd = mul_u64_u64_div_u64(period_ns, clk_get_rate(priv->clk), (u64)NSEC_PER_SEC * (prescaler + 1)); + if (!prd) + return -EINVAL; /* * All channels share the same prescaler and counter so when two @@ -673,7 +681,8 @@ static int stm32_pwm_probe(struct platform_device *pdev) * .apply() won't overflow. */ if (clk_get_rate(priv->clk) > 1000000000) - return dev_err_probe(dev, -EINVAL, "Failed to lock clock\n"); + return dev_err_probe(dev, -EINVAL, "Clock freq too high (%lu)\n", + clk_get_rate(priv->clk)); chip->ops = &stm32pwm_ops; |