| Message ID | 065aa239ba7e10b64f1c563aba08626f5de790ba.1610882271.git.baruch@tkos.co.il (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | gpio: mvebu: pwm fixes and improvements | expand |
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/ > 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> > --- > 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); > > 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
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); - 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); 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) 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 == (unsigned long long) UINT_MAX+1) + on = 0; + else if (val) on = val; else on = 1; @@ -714,9 +718,11 @@ 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 > (unsigned long long) UINT_MAX+1) return -EINVAL; - if (val) + if (val == (unsigned long long) UINT_MAX+1) + off = 0; + else if (val) off = val; else off = 1;
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. 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> --- drivers/gpio/gpio-mvebu.c | 38 ++++++++++++++++++++++---------------- 1 file changed, 22 insertions(+), 16 deletions(-)