SL28CPLD_PWM_CTRL_PRESCALER_MASK
prescaler = FIELD_GET(SL28CPLD_PWM_CTRL_PRESCALER_MASK, reg);
if (prescaler > field_max(SL28CPLD_PWM_CTRL_PRESCALER_MASK))
ctrl = FIELD_PREP(SL28CPLD_PWM_CTRL_PRESCALER_MASK, prescaler);
ctrl &= ~SL28CPLD_PWM_CTRL_PRESCALER_MASK;
ctrl |= FIELD_PREP(SL28CPLD_PWM_CTRL_PRESCALER_MASK, 1);