Re: [PATCH v4 5/5] gpio: mvebu: improve handling of pwm zero on/off values
From: Uwe Kleine-König <hidden>
Date: 2021-01-19 19:41:02
Also in:
linux-gpio, linux-pwm
Hello Baruch, On Sun, Jan 17, 2021 at 03:17:06PM +0200, Baruch Siach wrote:
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_sate to handle zero as a special case.
s/get_sate/get_state/
quoted hunk ↗ jump to hunk
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 <redacted> Analyzed-by: Russell King [off-list ref] Signed-off-by: Baruch Siach <baruch@tkos.co.il> --- drivers/gpio/gpio-mvebu.c | 38 ++++++++++++++++++++++---------------- 1 file changed, 22 insertions(+), 16 deletions(-)diff --git a/drivers/gpio/gpio-mvebu.c b/drivers/gpio/gpio-mvebu.c index 6b017854ce61..37f5bd65062f 100644 --- a/drivers/gpio/gpio-mvebu.c +++ b/drivers/gpio/gpio-mvebu.c@@ -667,22 +667,20 @@ 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 = (unsigned long long) u * NSEC_PER_SEC; else - state->duty_cycle = 1; + val = ((unsigned long long) UINT_MAX+1) * NSEC_PER_SEC; + state->duty_cycle = DIV_ROUND_UP_ULL(val, mvpwm->clk_rate);
Instead of if (u > 0) val = (unsigned long long) u * NSEC_PER_SEC; else val = ((unsigned long long) UINT_MAX+1) * NSEC_PER_SEC; state->duty_cycle = DIV_ROUND_UP_ULL(val, mvpwm->clk_rate); you could also write if (u > 0) val = u; else val = UINT_MAX + 1; state->duty_cycle = DIV_ROUND_UP_ULL(val * NSEC_PER_SEC, mvpwm->clk_rate); which is a bit lighter (IMHO).
- 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 += (unsigned long long) u * NSEC_PER_SEC; else - state->period = 1; + val += ((unsigned long long) UINT_MAX+1) * NSEC_PER_SEC; + state->period = DIV_ROUND_UP_ULL(val, mvpwm->clk_rate);
quoted hunk ↗ jump to hunk
regmap_read(mvchip->regs, GPIO_BLINK_EN_OFF + mvchip->offset, &u); if (u)@@ -704,9 +702,15 @@ 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 > (unsigned long long) UINT_MAX+1)
Please add whitespace around the + Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | https://www.pengutronix.de/ |