| From 6e9d3924d4dd83254426f8ae6d978a395985be76 Mon Sep 17 00:00:00 2001 |
| From: Fabrice Gasnier <fabrice.gasnier@st.com> |
| Date: Wed, 18 Sep 2019 16:54:21 +0200 |
| Subject: [PATCH] pwm: stm32-lp: Add check in case requested period cannot be |
| achieved |
| MIME-Version: 1.0 |
| Content-Type: text/plain; charset=UTF-8 |
| Content-Transfer-Encoding: 8bit |
| |
| commit c91e3234c6035baf5a79763cb4fcd5d23ce75c2b upstream. |
| |
| 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-Kรถnig <u.kleine-koenig@pengutronix.de> |
| Signed-off-by: Thierry Reding <thierry.reding@gmail.com> |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| |
| diff --git a/drivers/pwm/pwm-stm32-lp.c b/drivers/pwm/pwm-stm32-lp.c |
| index 0059b24cfdc3..28e1f6413476 100644 |
| --- a/drivers/pwm/pwm-stm32-lp.c |
| +++ b/drivers/pwm/pwm-stm32-lp.c |
| @@ -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++; |
| -- |
| 2.7.4 |
| |
