Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 5.7 351/376] pwm: jz4740: Enhance precision in calculation of duty cycle | Date | Fri, 19 Jun 2020 16:34:29 +0200 |
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From: Paul Cercueil <paul@crapouillou.net>
commit 9017dc4fbd59c09463019ce494cfe36d654495a8 upstream.
Calculating the hardware value for the duty from the hardware value of the period resulted in a precision loss versus calculating it from the clock rate directly.
(Also remove a cast that doesn't really need to be here)
Fixes: f6b8a5700057 ("pwm: Add Ingenic JZ4740 support") Cc: <stable@vger.kernel.org> Suggested-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Signed-off-by: Paul Cercueil <paul@crapouillou.net> Signed-off-by: Thierry Reding <thierry.reding@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- drivers/pwm/pwm-jz4740.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
--- a/drivers/pwm/pwm-jz4740.c +++ b/drivers/pwm/pwm-jz4740.c @@ -158,11 +158,11 @@ static int jz4740_pwm_apply(struct pwm_c /* Calculate period value */ tmp = (unsigned long long)rate * state->period; do_div(tmp, NSEC_PER_SEC); - period = (unsigned long)tmp; + period = tmp; /* Calculate duty value */ - tmp = (unsigned long long)period * state->duty_cycle; - do_div(tmp, state->period); + tmp = (unsigned long long)rate * state->duty_cycle; + do_div(tmp, NSEC_PER_SEC); duty = period - tmp; if (duty >= period)
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