From mboxrd@z Thu Jan 1 00:00:00 1970 From: megous@megous.com Subject: [PATCH] pwm: sun4i: Fix incorrect calculation of duty_cycle/period Date: Mon, 14 Oct 2019 15:53:03 +0200 Message-ID: <20191014135303.2944058-1-megous@megous.com> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: Sender: linux-kernel-owner@vger.kernel.org Cc: Ondrej Jirman , Thierry Reding , =?UTF-8?q?Uwe=20Kleine-K=C3=B6nig?= , Maxime Ripard , Chen-Yu Tsai , "open list:PWM SUBSYSTEM" , "moderated list:ARM/Allwinner sunXi SoC support" , open list List-Id: linux-pwm@vger.kernel.org From: Ondrej Jirman Since 5.4-rc1, pwm_apply_state calls ->get_state after ->apply if available, and this revealed an issue with integer precision when calculating duty_cycle and period for the currently set state in ->get_state callback. This issue manifested in broken backlight on several Allwinner based devices. Previously this worked, because ->apply updated the passed state directly. Fixes: deb9c462f4e53 ("pwm: sun4i: Don't update the state for the caller of pwm_apply_state") Signed-off-by: Ondrej Jirman --- drivers/pwm/pwm-sun4i.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/pwm/pwm-sun4i.c b/drivers/pwm/pwm-sun4i.c index 6f5840a1a82d..05273725a9ff 100644 --- a/drivers/pwm/pwm-sun4i.c +++ b/drivers/pwm/pwm-sun4i.c @@ -137,10 +137,10 @@ static void sun4i_pwm_get_state(struct pwm_chip *chip, val = sun4i_pwm_readl(sun4i_pwm, PWM_CH_PRD(pwm->hwpwm)); - tmp = prescaler * NSEC_PER_SEC * PWM_REG_DTY(val); + tmp = (u64)prescaler * NSEC_PER_SEC * PWM_REG_DTY(val); state->duty_cycle = DIV_ROUND_CLOSEST_ULL(tmp, clk_rate); - tmp = prescaler * NSEC_PER_SEC * PWM_REG_PRD(val); + tmp = (u64)prescaler * NSEC_PER_SEC * PWM_REG_PRD(val); state->period = DIV_ROUND_CLOSEST_ULL(tmp, clk_rate); } -- 2.23.0