diff options
| author | Baruch Siach <baruch@tkos.co.il> | 2021-01-20 18:16:28 +0200 |
|---|---|---|
| committer | Bartosz Golaszewski <bgolaszewski@baylibre.com> | 2021-02-15 11:43:30 +0100 |
| commit | 0b68d02b6a0dd2c7174a86a882e23d04fc7e7ca8 (patch) | |
| tree | 6a81816cbff192fe9fc244f047d067ca35f81273 /drivers/gpio | |
| parent | 2bee255a5ecf3213d118f22f6d8f65e4ec9101f2 (diff) | |
| download | linux-0b68d02b6a0dd2c7174a86a882e23d04fc7e7ca8.tar.bz2 | |
gpio: mvebu: improve handling of pwm zero on/off values
Hardware appears to treat zero value as 2^32. Take advantage of this
fact to support on/off values of up to UINT_MAX+1 == 2^32. Adjust both
.apply and .get_state to handle zero as a special case.
Rounded up division result in .get_state can't be zero, since the
dividend is now larger than 0. Remove check for this case.
Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Analyzed-by: Russell King <linux@armlinux.org.uk>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Diffstat (limited to 'drivers/gpio')
| -rw-r--r-- | drivers/gpio/gpio-mvebu.c | 39 |
1 files changed, 23 insertions, 16 deletions
diff --git a/drivers/gpio/gpio-mvebu.c b/drivers/gpio/gpio-mvebu.c index 6b017854ce61..75e3c235bd3a 100644 --- a/drivers/gpio/gpio-mvebu.c +++ b/drivers/gpio/gpio-mvebu.c @@ -667,22 +667,21 @@ static void mvebu_pwm_get_state(struct pwm_chip *chip, spin_lock_irqsave(&mvpwm->lock, flags); regmap_read(mvpwm->regs, mvebu_pwmreg_blink_on_duration(mvpwm), &u); - val = (unsigned long long) u * NSEC_PER_SEC; - val = DIV_ROUND_UP_ULL(val, mvpwm->clk_rate); - if (val) - state->duty_cycle = val; + /* Hardware treats zero as 2^32. See mvebu_pwm_apply(). */ + if (u > 0) + val = u; else - state->duty_cycle = 1; + val = UINT_MAX + 1ULL; + state->duty_cycle = DIV_ROUND_UP_ULL(val * NSEC_PER_SEC, + mvpwm->clk_rate); - val = (unsigned long long) u; /* on duration */ regmap_read(mvpwm->regs, mvebu_pwmreg_blink_off_duration(mvpwm), &u); - val += (unsigned long long) u; /* period = on + off duration */ - val *= NSEC_PER_SEC; - val = DIV_ROUND_UP_ULL(val, mvpwm->clk_rate); - if (val) - state->period = val; + /* period = on + off duration */ + if (u > 0) + val += u; else - state->period = 1; + val += UINT_MAX + 1ULL; + state->period = DIV_ROUND_UP_ULL(val * NSEC_PER_SEC, mvpwm->clk_rate); regmap_read(mvchip->regs, GPIO_BLINK_EN_OFF + mvchip->offset, &u); if (u) @@ -704,9 +703,15 @@ static int mvebu_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm, val = (unsigned long long) mvpwm->clk_rate * state->duty_cycle; do_div(val, NSEC_PER_SEC); - if (val > UINT_MAX) + if (val > UINT_MAX + 1ULL) return -EINVAL; - if (val) + /* + * Zero on/off values don't work as expected. Experimentation shows + * that zero value is treated as 2^32. This behavior is not documented. + */ + if (val == UINT_MAX + 1ULL) + on = 0; + else if (val) on = val; else on = 1; @@ -714,9 +719,11 @@ static int mvebu_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm, val = (unsigned long long) mvpwm->clk_rate * state->period; do_div(val, NSEC_PER_SEC); val -= on; - if (val > UINT_MAX) + if (val > UINT_MAX + 1ULL) return -EINVAL; - if (val) + if (val == UINT_MAX + 1ULL) + off = 0; + else if (val) off = val; else off = 1; |