From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sasha Levin Subject: [PATCH AUTOSEL 5.2 23/63] pwm: stm32-lp: Add check in case requested period cannot be achieved Date: Tue, 1 Oct 2019 12:40:45 -0400 Message-ID: <20191001164125.15398-23-sashal@kernel.org> References: <20191001164125.15398-1-sashal@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20191001164125.15398-1-sashal@kernel.org> Sender: linux-kernel-owner@vger.kernel.org To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Fabrice Gasnier , =?UTF-8?q?Uwe=20Kleine-K=C3=B6nig?= , Thierry Reding , Sasha Levin , linux-pwm@vger.kernel.org List-Id: linux-pwm@vger.kernel.org From: Fabrice Gasnier [ Upstream commit c91e3234c6035baf5a79763cb4fcd5d23ce75c2b ] 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 Reviewed-by: Uwe Kleine-König Signed-off-by: Thierry Reding Signed-off-by: Sasha Levin --- drivers/pwm/pwm-stm32-lp.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/pwm/pwm-stm32-lp.c b/drivers/pwm/pwm-stm32-lp.c index 0059b24cfdc3c..28e1f64134763 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++; -- 2.20.1