From: Andrew Bresticker <[email protected]> When possible, avoid setting the manual update bit and starting/stopping the PWM when adjusting the PWM as it causes noticable flickering when setting the backlight brightness.
Signed-off-by: Andrew Bresticker <[email protected]> Signed-off-by: Sachin Kamat <[email protected]> --- drivers/pwm/pwm-samsung.c | 23 +++++++++++++++++++---- 1 file changed, 19 insertions(+), 4 deletions(-) diff --git a/drivers/pwm/pwm-samsung.c b/drivers/pwm/pwm-samsung.c index b59639e..6d23eb3 100644 --- a/drivers/pwm/pwm-samsung.c +++ b/drivers/pwm/pwm-samsung.c @@ -34,6 +34,7 @@ #define REG_TCNTB(chan) (0x0c + ((chan) * 0xc)) #define REG_TCMPB(chan) (0x10 + ((chan) * 0xc)) +#define REG_TCNTO(chan) (0x14 + ((chan) * 0xc)) #define TCFG0_PRESCALER_MASK 0xff #define TCFG0_PRESCALER1_SHIFT 8 @@ -234,15 +235,29 @@ static int pwm_samsung_enable(struct pwm_chip *chip, struct pwm_device *pwm) struct samsung_pwm_chip *our_chip = to_samsung_pwm_chip(chip); unsigned int tcon_chan = to_tcon_channel(pwm->hwpwm); unsigned long flags; - u32 tcon; + u32 tcon, tcnt, tcnt_o; spin_lock_irqsave(&samsung_pwm_lock, flags); tcon = readl(our_chip->base + REG_TCON); + tcnt = readl(our_chip->base + REG_TCNTB(pwm->hwpwm)); + tcnt_o = readl(our_chip->base + REG_TCNTO(pwm->hwpwm)); - tcon &= ~TCON_START(tcon_chan); - tcon |= TCON_MANUALUPDATE(tcon_chan); - writel(tcon, our_chip->base + REG_TCON); + /* + * If we've got a big value stuck in the PWM we need to adjust it using + * manualupdate. The start bit needs to be off for that to work + * properly so we only do this if strictly necessary since it can cause + * the PWM to blink. + * + * We will also use manualupdate if we find that the autoreload bit + * wasn't set previously since the very first time the timer is + * configured we seem to need to kickstart the PWM. + */ + if ((tcnt_o > tcnt) || !(tcon & TCON_AUTORELOAD(tcon_chan))) { + tcon &= ~TCON_START(tcon_chan); + tcon |= TCON_MANUALUPDATE(tcon_chan); + writel(tcon, our_chip->base + REG_TCON); + } tcon &= ~TCON_MANUALUPDATE(tcon_chan); tcon |= TCON_START(tcon_chan) | TCON_AUTORELOAD(tcon_chan); -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
