gpio: mvebu: fix pwm .get_state period calculation

BugLink: https://bugs.launchpad.net/bugs/1915200
commit e73b0101ae5124bf7cd3fb5d250302ad2f16a416 upstream.

The period is the sum of on and off values. That is, calculate period as

  ($on + $off) / clkrate

instead of

  $off / clkrate - $on / clkrate

that makes no sense.

Reported-by: Russell King <linux@armlinux.org.uk>
Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Fixes: 757642f9a584e ("gpio: mvebu: Add limited PWM support")
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
[baruch: backport to kernels <= v5.10]
Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: William Breathitt Gray <william.gray@canonical.com>

diff --git a/drivers/gpio/gpio-mvebu.c b/drivers/gpio/gpio-mvebu.c
index 3985d6e1c17dc603c6e539dd889ee8898326b5a3..89a053b1d27994ffacccf9140b575f4e31aed7fc 100644 (file)
--- a/drivers/gpio/gpio-mvebu.c
+++ b/drivers/gpio/gpio-mvebu.c
@@ -657,9 +657,8 @@ static void mvebu_pwm_get_state(struct pwm_chip *chip,
 
        spin_lock_irqsave(&mvpwm->lock, flags);
 
-       val = (unsigned long long)
-               readl_relaxed(mvebu_pwmreg_blink_on_duration(mvpwm));
-       val *= NSEC_PER_SEC;
+       u = readl_relaxed(mvebu_pwmreg_blink_on_duration(mvpwm));
+       val = (unsigned long long) u * NSEC_PER_SEC;
        do_div(val, mvpwm->clk_rate);
        if (val > UINT_MAX)
                state->duty_cycle = UINT_MAX;
@@ -668,21 +667,17 @@ static void mvebu_pwm_get_state(struct pwm_chip *chip,
        else
                state->duty_cycle = 1;
 
-       val = (unsigned long long)
-               readl_relaxed(mvebu_pwmreg_blink_off_duration(mvpwm));
+       val = (unsigned long long) u; /* on duration */
+       /* period = on + off duration */
+       val += readl_relaxed(mvebu_pwmreg_blink_off_duration(mvpwm));
        val *= NSEC_PER_SEC;
        do_div(val, mvpwm->clk_rate);
-       if (val < state->duty_cycle) {
+       if (val > UINT_MAX)
+               state->period = UINT_MAX;
+       else if (val)
+               state->period = val;
+       else
                state->period = 1;
-       } else {
-               val -= state->duty_cycle;
-               if (val > UINT_MAX)
-                       state->period = UINT_MAX;
-               else if (val)
-                       state->period = val;
-               else
-                       state->period = 1;
-       }
 
        regmap_read(mvchip->regs, GPIO_BLINK_EN_OFF + mvchip->offset, &u);
        if (u)