pwm: lpss: Prevent on_time_div overflow on lower frequencies

[cascardo/linux.git] / drivers / pwm / pwm-lpss.c

diff --git a/drivers/pwm/pwm-lpss.c b/drivers/pwm/pwm-lpss.c
index 295b963..be4658b 100644 (file)
--- a/drivers/pwm/pwm-lpss.c
+++ b/drivers/pwm/pwm-lpss.c
@@ -27,7 +27,6 @@
 #define PWM_SW_UPDATE                  BIT(30)
 #define PWM_BASE_UNIT_SHIFT            8
 #define PWM_ON_TIME_DIV_MASK           0x000000ff
-#define PWM_DIVISION_CORRECTION                0x2
 
 /* Size of each PWM register space if multiple */
 #define PWM_SIZE                       0x400
@@ -92,7 +91,7 @@ static int pwm_lpss_config(struct pwm_chip *chip, struct pwm_device *pwm,
                           int duty_ns, int period_ns)
 {
        struct pwm_lpss_chip *lpwm = to_lpwm(chip);
-       u8 on_time_div;
+       unsigned long long on_time_div;
        unsigned long c, base_unit_range;
        unsigned long long base_unit, freq = NSEC_PER_SEC;
        u32 ctrl;
@@ -101,21 +100,22 @@ static int pwm_lpss_config(struct pwm_chip *chip, struct pwm_device *pwm,
 
        /*
         * The equation is:
-        * base_unit = ((freq / c) * base_unit_range) + correction
+        * base_unit = round(base_unit_range * freq / c)
         */
        base_unit_range = BIT(lpwm->info->base_unit_bits);
-       base_unit = freq * base_unit_range;
+       freq *= base_unit_range;
 
        c = lpwm->info->clk_rate;
        if (!c)
                return -EINVAL;
 
-       do_div(base_unit, c);
-       base_unit += PWM_DIVISION_CORRECTION;
+       base_unit = DIV_ROUND_CLOSEST_ULL(freq, c);
 
        if (duty_ns <= 0)
                duty_ns = 1;
-       on_time_div = 255 - (255 * duty_ns / period_ns);
+       on_time_div = 255ULL * duty_ns;
+       do_div(on_time_div, period_ns);
+       on_time_div = 255ULL - on_time_div;
 
        pm_runtime_get_sync(chip->dev);