github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-06-08 14:42:37 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

pwm: stm32-lp: Add check in case requested period cannot be achieved

Browse Source 
[ Upstream commit c91e3234c6 ]

LPTimer can use a 32KHz clock for counting. It depends on clock tree
configuration. In such a case, PWM output frequency range is limited.
Although unlikely, nothing prevents user from requesting a PWM frequency
above counting clock (32KHz for instance):
- This causes (prd - 1) = 0xffff to be written in ARR register later in
the apply() routine.
This results in badly configured PWM period (and also duty_cycle).
Add a check to report an error is such a case.

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Fabrice Gasnier 2019-09-18 16:54:21 +02:00 committed by Greg Kroah-Hartman
parent 19b1c70e91
commit 6534865953
1 changed files with 6 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
drivers/pwm/pwm-stm32-lp.c
View File

@ -58,6 +58,12 @@ static int stm32_pwm_lp_apply(struct pwm_chip *chip, struct pwm_device *pwm,
/* Calculate the period and prescaler value */
div = (unsigned long long)clk_get_rate(priv->clk) * state->period;
do_div(div, NSEC_PER_SEC);
if (!div) {
/* Clock is too slow to achieve requested period. */
dev_dbg(priv->chip.dev, "Can't reach %u ns\n", state->period);
return -EINVAL;
}
prd = div;
while (div > STM32_LPTIM_MAX_ARR) {
presc++;