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authorAndy Shevchenko <andriy.shevchenko@linux.intel.com>2017-01-28 17:10:39 +0200
committerThierry Reding <thierry.reding@gmail.com>2017-01-30 08:13:19 +0100
commit684309e5043efaaa94d9b4e65f53f7fdde1f6675 (patch)
tree8f25bbc38fbe2e2c2ecb2c3f8b11aca68404853b /drivers/pwm
parent8d254a340efb12b40c4c1ff25a48a4f48f7bbd6b (diff)
pwm: lpss: Avoid potential overflow of base_unit
The resolution of base_unit is derived from base_unit_bits and thus must be equal to (2^base_unit_bits - 1). Otherwise frequency and therefore base_unit might potentially overflow. Prevent the above by substracting 1 in all cases where base_unit_bits or derivative is used. Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
Diffstat (limited to 'drivers/pwm')
-rw-r--r--drivers/pwm/pwm-lpss.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/drivers/pwm/pwm-lpss.c b/drivers/pwm/pwm-lpss.c
index 72c0bce5a75c..8642feeb8abd 100644
--- a/drivers/pwm/pwm-lpss.c
+++ b/drivers/pwm/pwm-lpss.c
@@ -102,7 +102,7 @@ static int pwm_lpss_config(struct pwm_chip *chip, struct pwm_device *pwm,
* The equation is:
* base_unit = round(base_unit_range * freq / c)
*/
- base_unit_range = BIT(lpwm->info->base_unit_bits);
+ base_unit_range = BIT(lpwm->info->base_unit_bits) - 1;
freq *= base_unit_range;
base_unit = DIV_ROUND_CLOSEST_ULL(freq, c);
@@ -117,8 +117,8 @@ static int pwm_lpss_config(struct pwm_chip *chip, struct pwm_device *pwm,
ctrl = pwm_lpss_read(pwm);
ctrl &= ~PWM_ON_TIME_DIV_MASK;
- ctrl &= ~((base_unit_range - 1) << PWM_BASE_UNIT_SHIFT);
- base_unit &= (base_unit_range - 1);
+ ctrl &= ~(base_unit_range << PWM_BASE_UNIT_SHIFT);
+ base_unit &= base_unit_range;
ctrl |= (u32) base_unit << PWM_BASE_UNIT_SHIFT;
ctrl |= on_time_div;
pwm_lpss_write(pwm, ctrl);