The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From 9017dc4fbd59c09463019ce494cfe36d654495a8 Mon Sep 17 00:00:00 2001
From: Paul Cercueil <paul@xxxxxxxxxxxxxxx>
Date: Wed, 27 May 2020 13:52:23 +0200
Subject: [PATCH] pwm: jz4740: Enhance precision in calculation of duty cycle
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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@xxxxxxxxxxxxxxx>
Suggested-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
Reviewed-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
Signed-off-by: Paul Cercueil <paul@xxxxxxxxxxxxxxx>
Signed-off-by: Thierry Reding <thierry.reding@xxxxxxxxx>
diff --git a/drivers/pwm/pwm-jz4740.c b/drivers/pwm/pwm-jz4740.c
index 3cd5c054ad9a..4fe9d99ac9a9 100644
--- a/drivers/pwm/pwm-jz4740.c
+++ b/drivers/pwm/pwm-jz4740.c
@@ -158,11 +158,11 @@ static int jz4740_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
/* 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)
