* 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;