From: Ondrej Jirman megous@megous.com
[ Upstream commit 50cc7e3e4f26e3bf5ed74a8d061195c4d2161b8b ]
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 megous@megous.com Acked-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 --- 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 6f5840a1a82dc..05273725a9fff 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); }