On Wed, Oct 30, 2013 at 10:21:44AM +0530, Sachin Kamat wrote:
> From: Andrew Bresticker <abrestic@xxxxxxxxxxxx>
>
> 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 <abrestic@xxxxxxxxxxxx>
> Signed-off-by: Sachin Kamat <sachin.kamat@xxxxxxxxxx>
> ---
> drivers/pwm/pwm-samsung.c | 23 +++++++++++++++++++----
> 1 file changed, 19 insertions(+), 4 deletions(-)
There has been no comment on this, so can I assume this is fine with
everyone?
Thierry
> 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
>
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