| Message ID | 20181017045635.9857-3-anarsoul@gmail.com |
|---|---|
| State | Accepted |
| Commit | c33ba7ec8b9be0a6fe7a2bd47a36c991bf9189e1 |
| Delegated to: | Jagannadha Sutradharudu Teki |
| Headers | show |
| Series | [U-Boot,1/3] pwm: sunxi: fix off-by-one that prevented PWM to use prescaler bypass | expand |
On 2018-10-16, Vasily Khoruzhick wrote: > Choose best prescaler to improve PWM resolution. Without this change > driver chooses first prescaler that gives us period value within > range, but it could be not the best one. > > Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com> Fixes LCD backlight issues with the pinebook series: https://patchwork.ozlabs.org/project/uboot/list/?series=71358 Tested-by: Vagrant Cascadian <vagrant@debian.org> > --- > drivers/pwm/sunxi_pwm.c | 32 +++++++++++++++++++------------- > 1 file changed, 19 insertions(+), 13 deletions(-) > > diff --git a/drivers/pwm/sunxi_pwm.c b/drivers/pwm/sunxi_pwm.c > index 6284409b4f..8a55e4f461 100644 > --- a/drivers/pwm/sunxi_pwm.c > +++ b/drivers/pwm/sunxi_pwm.c > @@ -67,49 +67,55 @@ static int sunxi_pwm_set_config(struct udevice *dev, uint channel, > { > struct sunxi_pwm_priv *priv = dev_get_priv(dev); > struct sunxi_pwm *regs = priv->regs; > - int prescaler; > - u32 v, period = 0, duty; > - u64 scaled_freq = 0; > + int best_prescaler = 0; > + u32 v, best_period = 0, duty; > + u64 best_scaled_freq = 0; > const u32 nsecs_per_sec = 1000000000U; > > debug("%s: period_ns=%u, duty_ns=%u\n", __func__, period_ns, duty_ns); > > - for (prescaler = 0; prescaler <= SUNXI_PWM_CTRL_PRESCALE0_MASK; > + for (int prescaler = 0; prescaler <= SUNXI_PWM_CTRL_PRESCALE0_MASK; > prescaler++) { > + u32 period = 0; > + u64 scaled_freq = 0; > if (!prescaler_table[prescaler]) > continue; > scaled_freq = lldiv(OSC_24MHZ, prescaler_table[prescaler]); > period = lldiv(scaled_freq * period_ns, nsecs_per_sec); > - if (period - 1 <= SUNXI_PWM_CH0_PERIOD_MAX) > - break; > + if ((period - 1 <= SUNXI_PWM_CH0_PERIOD_MAX) && > + best_period < period) { > + best_period = period; > + best_scaled_freq = scaled_freq; > + best_prescaler = prescaler; > + } > } > > - if (period - 1 > SUNXI_PWM_CH0_PERIOD_MAX) { > + if (best_period - 1 > SUNXI_PWM_CH0_PERIOD_MAX) { > debug("%s: failed to find prescaler value\n", __func__); > return -EINVAL; > } > > - duty = lldiv(scaled_freq * duty_ns, nsecs_per_sec); > + duty = lldiv(best_scaled_freq * duty_ns, nsecs_per_sec); > > - if (priv->prescaler != prescaler) { > + if (priv->prescaler != best_prescaler) { > /* Mask clock to update prescaler */ > v = readl(®s->ctrl); > v &= ~SUNXI_PWM_CTRL_CLK_GATE; > writel(v, ®s->ctrl); > v &= ~SUNXI_PWM_CTRL_PRESCALE0_MASK; > - v |= (prescaler & SUNXI_PWM_CTRL_PRESCALE0_MASK); > + v |= (best_prescaler & SUNXI_PWM_CTRL_PRESCALE0_MASK); > writel(v, ®s->ctrl); > v |= SUNXI_PWM_CTRL_CLK_GATE; > writel(v, ®s->ctrl); > - priv->prescaler = prescaler; > + priv->prescaler = best_prescaler; > } > > - writel(SUNXI_PWM_CH0_PERIOD_PRD(period) | > + writel(SUNXI_PWM_CH0_PERIOD_PRD(best_period) | > SUNXI_PWM_CH0_PERIOD_DUTY(duty), ®s->ch0_period); > > debug("%s: prescaler: %d, period: %d, duty: %d\n", > __func__, priv->prescaler, > - period, duty); > + best_period, duty); > > return 0; > }
On Wed, Oct 17, 2018 at 10:28 AM Vasily Khoruzhick <anarsoul@gmail.com> wrote: > > Choose best prescaler to improve PWM resolution. Without this change > driver chooses first prescaler that gives us period value within > range, but it could be not the best one. This commit need to elaborate about the real issue, ie got fixed. Understand it has chosen best prescaler but why and how it.
On Mon, Oct 22, 2018 at 11:29 AM Jagan Teki <jagan@amarulasolutions.com> wrote: > > On Wed, Oct 17, 2018 at 10:28 AM Vasily Khoruzhick <anarsoul@gmail.com> wrote: > > > > Choose best prescaler to improve PWM resolution. Without this change > > driver chooses first prescaler that gives us period value within > > range, but it could be not the best one. > > This commit need to elaborate about the real issue, ie got fixed. > Understand it has chosen best prescaler but why and how it. If PWM resolution is low then close backlight levels can result in the same PWM settings, i.e. 0% and 10% can be the same (and thus backlight remains powered off). Basically the patch does what comment says - it improves PWM resolution.
On Wed, Oct 17, 2018 at 10:28 AM Vasily Khoruzhick <anarsoul@gmail.com> wrote: > > Choose best prescaler to improve PWM resolution. Without this change > driver chooses first prescaler that gives us period value within > range, but it could be not the best one. > > Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com> > --- Applied to all to u-boot-sunxi/master
I think this series already went into Anatolij's u-boot-staging/agust@denx.de, please make sure that you don't introduce any conflicts.On Wed, Oct 24, 2018 at 9:28 AM Jagan Teki <jagan@amarulasolutions.com> wrote: > > On Wed, Oct 17, 2018 at 10:28 AM Vasily Khoruzhick <anarsoul@gmail.com> wrote: > > > > Choose best prescaler to improve PWM resolution. Without this change > > driver chooses first prescaler that gives us period value within > > range, but it could be not the best one. > > > > Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com> > > --- > > Applied to all to u-boot-sunxi/master
diff --git a/drivers/pwm/sunxi_pwm.c b/drivers/pwm/sunxi_pwm.c index 6284409b4f..8a55e4f461 100644 --- a/drivers/pwm/sunxi_pwm.c +++ b/drivers/pwm/sunxi_pwm.c @@ -67,49 +67,55 @@ static int sunxi_pwm_set_config(struct udevice *dev, uint channel, { struct sunxi_pwm_priv *priv = dev_get_priv(dev); struct sunxi_pwm *regs = priv->regs; - int prescaler; - u32 v, period = 0, duty; - u64 scaled_freq = 0; + int best_prescaler = 0; + u32 v, best_period = 0, duty; + u64 best_scaled_freq = 0; const u32 nsecs_per_sec = 1000000000U; debug("%s: period_ns=%u, duty_ns=%u\n", __func__, period_ns, duty_ns); - for (prescaler = 0; prescaler <= SUNXI_PWM_CTRL_PRESCALE0_MASK; + for (int prescaler = 0; prescaler <= SUNXI_PWM_CTRL_PRESCALE0_MASK; prescaler++) { + u32 period = 0; + u64 scaled_freq = 0; if (!prescaler_table[prescaler]) continue; scaled_freq = lldiv(OSC_24MHZ, prescaler_table[prescaler]); period = lldiv(scaled_freq * period_ns, nsecs_per_sec); - if (period - 1 <= SUNXI_PWM_CH0_PERIOD_MAX) - break; + if ((period - 1 <= SUNXI_PWM_CH0_PERIOD_MAX) && + best_period < period) { + best_period = period; + best_scaled_freq = scaled_freq; + best_prescaler = prescaler; + } } - if (period - 1 > SUNXI_PWM_CH0_PERIOD_MAX) { + if (best_period - 1 > SUNXI_PWM_CH0_PERIOD_MAX) { debug("%s: failed to find prescaler value\n", __func__); return -EINVAL; } - duty = lldiv(scaled_freq * duty_ns, nsecs_per_sec); + duty = lldiv(best_scaled_freq * duty_ns, nsecs_per_sec); - if (priv->prescaler != prescaler) { + if (priv->prescaler != best_prescaler) { /* Mask clock to update prescaler */ v = readl(®s->ctrl); v &= ~SUNXI_PWM_CTRL_CLK_GATE; writel(v, ®s->ctrl); v &= ~SUNXI_PWM_CTRL_PRESCALE0_MASK; - v |= (prescaler & SUNXI_PWM_CTRL_PRESCALE0_MASK); + v |= (best_prescaler & SUNXI_PWM_CTRL_PRESCALE0_MASK); writel(v, ®s->ctrl); v |= SUNXI_PWM_CTRL_CLK_GATE; writel(v, ®s->ctrl); - priv->prescaler = prescaler; + priv->prescaler = best_prescaler; } - writel(SUNXI_PWM_CH0_PERIOD_PRD(period) | + writel(SUNXI_PWM_CH0_PERIOD_PRD(best_period) | SUNXI_PWM_CH0_PERIOD_DUTY(duty), ®s->ch0_period); debug("%s: prescaler: %d, period: %d, duty: %d\n", __func__, priv->prescaler, - period, duty); + best_period, duty); return 0; }
Choose best prescaler to improve PWM resolution. Without this change driver chooses first prescaler that gives us period value within range, but it could be not the best one. Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com> --- drivers/pwm/sunxi_pwm.c | 32 +++++++++++++++++++------------- 1 file changed, 19 insertions(+), 13 deletions(-)