[U-Boot] [PATCH 1/3] pwm: sunxi: fix off-by-one that prevented PWM to use prescaler bypass

[U-Boot] [PATCH 1/3] pwm: sunxi: fix off-by-one that prevented PWM to use prescaler bypass

[Vasily Khoruzhick]

Fix off-by-one that prevented PWM driver to use prescaler bypass.
Without this change prescaler is always enabled.

Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com>
---
 drivers/pwm/sunxi_pwm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pwm/sunxi_pwm.c b/drivers/pwm/sunxi_pwm.c
index 3c7dffdd90..baee503730 100644
--- a/drivers/pwm/sunxi_pwm.c
+++ b/drivers/pwm/sunxi_pwm.c
@@ -74,7 +74,7 @@ static int sunxi_pwm_set_config(struct udevice *dev, uint channel,
 
 	debug("%s: period_ns=%u, duty_ns=%u\n", __func__, period_ns, duty_ns);
 
-	for (prescaler = 0; prescaler < SUNXI_PWM_CTRL_PRESCALE0_MASK;
+	for (prescaler = 0; prescaler <= SUNXI_PWM_CTRL_PRESCALE0_MASK;
 	     prescaler++) {
 		if (!prescaler_table[prescaler])
 			continue;
-- 
2.19.0

[U-Boot] [PATCH 2/3] pwm: sunxi: use new prescaler when configuring PWM

[Vasily Khoruzhick]

Looks like old prescaler was used when configuring PWM, fix it.

Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com>
---
 drivers/pwm/sunxi_pwm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pwm/sunxi_pwm.c b/drivers/pwm/sunxi_pwm.c
index baee503730..6284409b4f 100644
--- a/drivers/pwm/sunxi_pwm.c
+++ b/drivers/pwm/sunxi_pwm.c
@@ -97,7 +97,7 @@ static int sunxi_pwm_set_config(struct udevice *dev, uint channel,
 		v &= ~SUNXI_PWM_CTRL_CLK_GATE;
 		writel(v, &regs->ctrl);
 		v &= ~SUNXI_PWM_CTRL_PRESCALE0_MASK;
-		v |= (priv->prescaler & SUNXI_PWM_CTRL_PRESCALE0_MASK);
+		v |= (prescaler & SUNXI_PWM_CTRL_PRESCALE0_MASK);
 		writel(v, &regs->ctrl);
 		v |= SUNXI_PWM_CTRL_CLK_GATE;
 		writel(v, &regs->ctrl);
-- 
2.19.0

[U-Boot] [PATCH 3/3] pwm: sunxi: choose best prescaler to improve PWM resolution

[Vasily Khoruzhick]

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(-)

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(&regs->ctrl);
 		v &= ~SUNXI_PWM_CTRL_CLK_GATE;
 		writel(v, &regs->ctrl);
 		v &= ~SUNXI_PWM_CTRL_PRESCALE0_MASK;
-		v |= (prescaler & SUNXI_PWM_CTRL_PRESCALE0_MASK);
+		v |= (best_prescaler & SUNXI_PWM_CTRL_PRESCALE0_MASK);
 		writel(v, &regs->ctrl);
 		v |= SUNXI_PWM_CTRL_CLK_GATE;
 		writel(v, &regs->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), &regs->ch0_period);
 
 	debug("%s: prescaler: %d, period: %d, duty: %d\n",
 	      __func__, priv->prescaler,
-	      period, duty);
+	      best_period, duty);
 
 	return 0;
 }
-- 
2.19.0

[U-Boot] [U-Boot, 3/3] pwm: sunxi: choose best prescaler to improve PWM resolution

[Vagrant Cascadian]

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(&regs->ctrl);
>  		v &= ~SUNXI_PWM_CTRL_CLK_GATE;
>  		writel(v, &regs->ctrl);
>  		v &= ~SUNXI_PWM_CTRL_PRESCALE0_MASK;
> -		v |= (prescaler & SUNXI_PWM_CTRL_PRESCALE0_MASK);
> +		v |= (best_prescaler & SUNXI_PWM_CTRL_PRESCALE0_MASK);
>  		writel(v, &regs->ctrl);
>  		v |= SUNXI_PWM_CTRL_CLK_GATE;
>  		writel(v, &regs->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), &regs->ch0_period);
>  
>  	debug("%s: prescaler: %d, period: %d, duty: %d\n",
>  	      __func__, priv->prescaler,
> -	      period, duty);
> +	      best_period, duty);
>  
>  	return 0;
>  }
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[U-Boot] [PATCH 3/3] pwm: sunxi: choose best prescaler to improve PWM resolution

[Jagan Teki]

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.

[U-Boot] [PATCH 3/3] pwm: sunxi: choose best prescaler to improve PWM resolution

[Vasily Khoruzhick]

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.

[U-Boot] [PATCH 3/3] pwm: sunxi: choose best prescaler to improve PWM resolution

[Jagan Teki]

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

[U-Boot] [PATCH 3/3] pwm: sunxi: choose best prescaler to improve PWM resolution

[Vasily Khoruzhick]

I think this series already went into Anatolij's
u-boot-staging/agust at 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

[U-Boot] [PATCH 1/3] pwm: sunxi: fix off-by-one that prevented PWM to use prescaler bypass

[Maxime Ripard]

On Tue, Oct 16, 2018 at 09:56:33PM -0700, Vasily Khoruzhick wrote:
> Fix off-by-one that prevented PWM driver to use prescaler bypass.
> Without this change prescaler is always enabled.
> 
> Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com>

For the whole series,
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>

Thanks!
Maxime

-- 
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

[U-Boot] [PATCH 1/3] pwm: sunxi: fix off-by-one that prevented PWM to use prescaler bypass

[Anatolij Gustschin]

On Tue, 16 Oct 2018 21:56:33 -0700
Vasily Khoruzhick anarsoul at gmail.com wrote:

> Fix off-by-one that prevented PWM driver to use prescaler bypass.
> Without this change prescaler is always enabled.
> 
> Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com>
> ---
>  drivers/pwm/sunxi_pwm.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Applied whole series to u-boot-staging/agust at denx.de, thanks!

--
Anatolij