[PATCH v8 0/3] Change PWM-controlled LED pin active mode and algorithm

[PATCH v8 0/3] Change PWM-controlled LED pin active mode and algorithm

[Nylon Chen]

According to the circuit diagram of User LEDs - RGB described in the
manual hifive-unleashed-a00.pdf[0] and hifive-unmatched-schematics-v3.pdf[1].

The behavior of PWM is acitve-high.

According to the descriptionof PWM for pwmcmp in SiFive FU740-C000 Manual[2].

The pwm algorithm is (PW) pulse active time  = (D) duty * (T) period.
The `frac` variable is pulse "inactive" time so we need to invert it.

So this patchset removes active-low in DTS and adds reverse logic to the driver.

Updated patches: 3
New patches: 0
Unchanged patches: 0

Links:
- [0]: https://sifive.cdn.prismic.io/sifive/c52a8e32-05ce-4aaf-95c8-7bf8453f8698_hifive-unleashed-a00-schematics-1.pdf
- [1]: https://sifive.cdn.prismic.io/sifive/6a06d6c0-6e66-49b5-8e9e-e68ce76f4192_hifive-unmatched-schematics-v3.pdf
- [2]: https://sifive.cdn.prismic.io/sifive/1a82e600-1f93-4f41-b2d8-86ed8b16acba_fu740-c000-manual-v1p6.pdf

Changed in v8:
 - Fix Signed-off-by and Co-developed-by typo.

Changed in v7:
 - Remove active-low strings from hifive-unleashed-a00.dts file.

Changed in v6:
 - Separate the idempotent test bug fixes into a new patch.
 - Move the reversing the duty before the line checking
   state->enabled.
 - Fix the algorithm and change it to take the minimum value first and
   then reverse it.

Changed in v5:
 - Add the updates to the PWM algorithm based on version 2 back in.
 - Replace div64_ul with DIV_ROUND_UP_ULL to correct the error in the
   period value of the idempotent test in pwm_apply_state_debug.

Changed in v4:
 - Remove previous updates to the PWM algorithm.

Changed in v3:
 - Convert the reference link to standard link.
 - Move the inverted function before taking the minimum value.
 - Change polarity check condition(high and low).
 - Pick the biggest period length possible that is not bigger than the
   requested period.

Changed in v2:
 - Convert the reference link to standard link.
 - Fix typo: s/sifive unmatched:/sifive: unmatched:/.
 - Remove active-low from hifive-unleashed-a00.dts.
 - Include this reference link in the dts and pwm commit messages.

Nylon Chen (3):
  riscv: dts: sifive: unleashed/unmatched: Remove PWM controlled LED's
    active-low properties
  pwm: sifive: change the PWM controlled LED algorithm
  pwm: sifive: Fix the error in the idempotent test within the
    pwm_apply_state_debug function

 arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dts | 12 ++++--------
 arch/riscv/boot/dts/sifive/hifive-unmatched-a00.dts | 12 ++++--------
 drivers/pwm/pwm-sifive.c                            |  9 +++++----
 3 files changed, 13 insertions(+), 20 deletions(-)

-- 
2.42.0

[PATCH v8 1/3] riscv: dts: sifive: unleashed/unmatched: Remove PWM controlled LED's active-low properties

[Nylon Chen]

This removes the active-low properties of the PWM-controlled LEDs in
the HiFive Unmatched device tree.

The reference is hifive-unleashed-a00.pdf[0] and hifive-unmatched-schematics-v3.pdf[1].

Link: https://sifive.cdn.prismic.io/sifive/c52a8e32-05ce-4aaf-95c8-7bf8453f8698_hifive-unleashed-a00-schematics-1.pdf [0]
Link: https://sifive.cdn.prismic.io/sifive/6a06d6c0-6e66-49b5-8e9e-e68ce76f4192_hifive-unmatched-schematics-v3.pdf [1]

Co-developed-by: Zong Li <zong.li@sifive.com>
Signed-off-by: Zong Li <zong.li@sifive.com>
Co-developed-by: Vincent Chen <vincent.chen@sifive.com>
Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
Signed-off-by: Nylon Chen <nylon.chen@sifive.com>
---
 arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dts | 12 ++++--------
 arch/riscv/boot/dts/sifive/hifive-unmatched-a00.dts | 12 ++++--------
 2 files changed, 8 insertions(+), 16 deletions(-)

diff --git a/arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dts b/arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dts
index 900a50526d77..06731b8c7bc3 100644
--- a/arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dts
+++ b/arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dts
@@ -49,32 +49,28 @@ led-controller {
 		compatible = "pwm-leds";
 
 		led-d1 {
-			pwms = <&pwm0 0 7812500 PWM_POLARITY_INVERTED>;
-			active-low;
+			pwms = <&pwm0 0 7812500 0>;
 			color = <LED_COLOR_ID_GREEN>;
 			max-brightness = <255>;
 			label = "d1";
 		};
 
 		led-d2 {
-			pwms = <&pwm0 1 7812500 PWM_POLARITY_INVERTED>;
-			active-low;
+			pwms = <&pwm0 1 7812500 0>;
 			color = <LED_COLOR_ID_GREEN>;
 			max-brightness = <255>;
 			label = "d2";
 		};
 
 		led-d3 {
-			pwms = <&pwm0 2 7812500 PWM_POLARITY_INVERTED>;
-			active-low;
+			pwms = <&pwm0 2 7812500 0>;
 			color = <LED_COLOR_ID_GREEN>;
 			max-brightness = <255>;
 			label = "d3";
 		};
 
 		led-d4 {
-			pwms = <&pwm0 3 7812500 PWM_POLARITY_INVERTED>;
-			active-low;
+			pwms = <&pwm0 3 7812500 0>;
 			color = <LED_COLOR_ID_GREEN>;
 			max-brightness = <255>;
 			label = "d4";
diff --git a/arch/riscv/boot/dts/sifive/hifive-unmatched-a00.dts b/arch/riscv/boot/dts/sifive/hifive-unmatched-a00.dts
index 07387f9c135c..b328ee80693f 100644
--- a/arch/riscv/boot/dts/sifive/hifive-unmatched-a00.dts
+++ b/arch/riscv/boot/dts/sifive/hifive-unmatched-a00.dts
@@ -51,8 +51,7 @@ led-controller-1 {
 		compatible = "pwm-leds";
 
 		led-d12 {
-			pwms = <&pwm0 0 7812500 PWM_POLARITY_INVERTED>;
-			active-low;
+			pwms = <&pwm0 0 7812500 0>;
 			color = <LED_COLOR_ID_GREEN>;
 			max-brightness = <255>;
 			label = "d12";
@@ -68,20 +67,17 @@ multi-led {
 			label = "d2";
 
 			led-red {
-				pwms = <&pwm0 2 7812500 PWM_POLARITY_INVERTED>;
-				active-low;
+				pwms = <&pwm0 2 7812500 0>;
 				color = <LED_COLOR_ID_RED>;
 			};
 
 			led-green {
-				pwms = <&pwm0 1 7812500 PWM_POLARITY_INVERTED>;
-				active-low;
+				pwms = <&pwm0 1 7812500 0>;
 				color = <LED_COLOR_ID_GREEN>;
 			};
 
 			led-blue {
-				pwms = <&pwm0 3 7812500 PWM_POLARITY_INVERTED>;
-				active-low;
+				pwms = <&pwm0 3 7812500 0>;
 				color = <LED_COLOR_ID_BLUE>;
 			};
 		};
-- 
2.42.0

Re: [PATCH v8 1/3] riscv: dts: sifive: unleashed/unmatched: Remove PWM controlled LED's active-low properties

[Conor Dooley]

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On Fri, Jan 26, 2024 at 03:40:43PM +0800, Nylon Chen wrote:
> This removes the active-low properties of the PWM-controlled LEDs in
> the HiFive Unmatched device tree.
> 
> The reference is hifive-unleashed-a00.pdf[0] and hifive-unmatched-schematics-v3.pdf[1].
> 
> Link: https://sifive.cdn.prismic.io/sifive/c52a8e32-05ce-4aaf-95c8-7bf8453f8698_hifive-unleashed-a00-schematics-1.pdf [0]
> Link: https://sifive.cdn.prismic.io/sifive/6a06d6c0-6e66-49b5-8e9e-e68ce76f4192_hifive-unmatched-schematics-v3.pdf [1]
> 
> Co-developed-by: Zong Li <zong.li@sifive.com>
> Signed-off-by: Zong Li <zong.li@sifive.com>
> Co-developed-by: Vincent Chen <vincent.chen@sifive.com>
> Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
> Signed-off-by: Nylon Chen <nylon.chen@sifive.com>

Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>

Uwe, take this with the driver, if that is ready to be taken.

Thanks,
Conor.

> ---
>  arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dts | 12 ++++--------
>  arch/riscv/boot/dts/sifive/hifive-unmatched-a00.dts | 12 ++++--------
>  2 files changed, 8 insertions(+), 16 deletions(-)
> 
> diff --git a/arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dts b/arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dts
> index 900a50526d77..06731b8c7bc3 100644
> --- a/arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dts
> +++ b/arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dts
> @@ -49,32 +49,28 @@ led-controller {
>  		compatible = "pwm-leds";
>  
>  		led-d1 {
> -			pwms = <&pwm0 0 7812500 PWM_POLARITY_INVERTED>;
> -			active-low;
> +			pwms = <&pwm0 0 7812500 0>;
>  			color = <LED_COLOR_ID_GREEN>;
>  			max-brightness = <255>;
>  			label = "d1";
>  		};
>  
>  		led-d2 {
> -			pwms = <&pwm0 1 7812500 PWM_POLARITY_INVERTED>;
> -			active-low;
> +			pwms = <&pwm0 1 7812500 0>;
>  			color = <LED_COLOR_ID_GREEN>;
>  			max-brightness = <255>;
>  			label = "d2";
>  		};
>  
>  		led-d3 {
> -			pwms = <&pwm0 2 7812500 PWM_POLARITY_INVERTED>;
> -			active-low;
> +			pwms = <&pwm0 2 7812500 0>;
>  			color = <LED_COLOR_ID_GREEN>;
>  			max-brightness = <255>;
>  			label = "d3";
>  		};
>  
>  		led-d4 {
> -			pwms = <&pwm0 3 7812500 PWM_POLARITY_INVERTED>;
> -			active-low;
> +			pwms = <&pwm0 3 7812500 0>;
>  			color = <LED_COLOR_ID_GREEN>;
>  			max-brightness = <255>;
>  			label = "d4";
> diff --git a/arch/riscv/boot/dts/sifive/hifive-unmatched-a00.dts b/arch/riscv/boot/dts/sifive/hifive-unmatched-a00.dts
> index 07387f9c135c..b328ee80693f 100644
> --- a/arch/riscv/boot/dts/sifive/hifive-unmatched-a00.dts
> +++ b/arch/riscv/boot/dts/sifive/hifive-unmatched-a00.dts
> @@ -51,8 +51,7 @@ led-controller-1 {
>  		compatible = "pwm-leds";
>  
>  		led-d12 {
> -			pwms = <&pwm0 0 7812500 PWM_POLARITY_INVERTED>;
> -			active-low;
> +			pwms = <&pwm0 0 7812500 0>;
>  			color = <LED_COLOR_ID_GREEN>;
>  			max-brightness = <255>;
>  			label = "d12";
> @@ -68,20 +67,17 @@ multi-led {
>  			label = "d2";
>  
>  			led-red {
> -				pwms = <&pwm0 2 7812500 PWM_POLARITY_INVERTED>;
> -				active-low;
> +				pwms = <&pwm0 2 7812500 0>;
>  				color = <LED_COLOR_ID_RED>;
>  			};
>  
>  			led-green {
> -				pwms = <&pwm0 1 7812500 PWM_POLARITY_INVERTED>;
> -				active-low;
> +				pwms = <&pwm0 1 7812500 0>;
>  				color = <LED_COLOR_ID_GREEN>;
>  			};
>  
>  			led-blue {
> -				pwms = <&pwm0 3 7812500 PWM_POLARITY_INVERTED>;
> -				active-low;
> +				pwms = <&pwm0 3 7812500 0>;
>  				color = <LED_COLOR_ID_BLUE>;
>  			};
>  		};
> -- 
> 2.42.0
> 

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[PATCH v8 2/3] pwm: sifive: change the PWM controlled LED algorithm

[Nylon Chen]

The `frac` variable represents the pulse inactive time, and the result
of this algorithm is the pulse active time. Therefore, we must reverse the result.

The reference is SiFive FU740-C000 Manual[0]

Link: https://sifive.cdn.prismic.io/sifive/1a82e600-1f93-4f41-b2d8-86ed8b16acba_fu740-c000-manual-v1p6.pdf [0]

Co-developed-by: Zong Li <zong.li@sifive.com>
Signed-off-by: Zong Li <zong.li@sifive.com>
Co-developed-by: Vincent Chen <vincent.chen@sifive.com>
Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
Signed-off-by: Nylon Chen <nylon.chen@sifive.com>
---
 drivers/pwm/pwm-sifive.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/pwm/pwm-sifive.c b/drivers/pwm/pwm-sifive.c
index eabddb7c7820..b07c8598bb21 100644
--- a/drivers/pwm/pwm-sifive.c
+++ b/drivers/pwm/pwm-sifive.c
@@ -113,6 +113,7 @@ static int pwm_sifive_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
 	u32 duty, val;
 
 	duty = readl(ddata->regs + PWM_SIFIVE_PWMCMP(pwm->hwpwm));
+	duty = (1U << PWM_SIFIVE_CMPWIDTH) - 1 - duty;
 
 	state->enabled = duty > 0;
 
@@ -123,11 +124,10 @@ static int pwm_sifive_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
 	state->period = ddata->real_period;
 	state->duty_cycle =
 		(u64)duty * ddata->real_period >> PWM_SIFIVE_CMPWIDTH;
-	state->polarity = PWM_POLARITY_INVERSED;
+	state->polarity = PWM_POLARITY_NORMAL;
 
 	return 0;
 }
-
 static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 			    const struct pwm_state *state)
 {
@@ -139,7 +139,7 @@ static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	int ret = 0;
 	u32 frac;
 
-	if (state->polarity != PWM_POLARITY_INVERSED)
+	if (state->polarity != PWM_POLARITY_NORMAL)
 		return -EINVAL;
 
 	cur_state = pwm->state;
@@ -159,6 +159,7 @@ static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	frac = DIV64_U64_ROUND_CLOSEST(num, state->period);
 	/* The hardware cannot generate a 100% duty cycle */
 	frac = min(frac, (1U << PWM_SIFIVE_CMPWIDTH) - 1);
+	frac = (1U << PWM_SIFIVE_CMPWIDTH) - 1 - frac;
 
 	mutex_lock(&ddata->lock);
 	if (state->period != ddata->approx_period) {
-- 
2.42.0

Re: [PATCH v8 2/3] pwm: sifive: change the PWM controlled LED algorithm

[Uwe Kleine-König]

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Hello,

Regarding the Subject: The patch has nothing to do with an LED, has it?

On Fri, Jan 26, 2024 at 03:40:44PM +0800, Nylon Chen wrote:
> The `frac` variable represents the pulse inactive time, and the result
> of this algorithm is the pulse active time. Therefore, we must reverse the result.

Please break lines at 75 columns in the commit log.

> The reference is SiFive FU740-C000 Manual[0]
> 
> Link: https://sifive.cdn.prismic.io/sifive/1a82e600-1f93-4f41-b2d8-86ed8b16acba_fu740-c000-manual-v1p6.pdf [0]

I looked at Figure 29 in this document (version v1p6, pdf page 148). Not
sure I understand that correctly, but I expect that the output of the
">=?" node below pwmcmp0 to become 1 if pwms has reached pwmcmp0, is
that right? In that case this output is zero when pwmcount is zero and
then pwmcmp0ip is zero, too. So a period starts with the inactive part
and so it's inversed polarity.

What made you think that the current driver implementation is wrong?

> Co-developed-by: Zong Li <zong.li@sifive.com>
> Signed-off-by: Zong Li <zong.li@sifive.com>
> Co-developed-by: Vincent Chen <vincent.chen@sifive.com>
> Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
> Signed-off-by: Nylon Chen <nylon.chen@sifive.com>
> ---
>  drivers/pwm/pwm-sifive.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/pwm/pwm-sifive.c b/drivers/pwm/pwm-sifive.c
> index eabddb7c7820..b07c8598bb21 100644
> --- a/drivers/pwm/pwm-sifive.c
> +++ b/drivers/pwm/pwm-sifive.c
> @@ -113,6 +113,7 @@ static int pwm_sifive_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
>  	u32 duty, val;
>  
>  	duty = readl(ddata->regs + PWM_SIFIVE_PWMCMP(pwm->hwpwm));
> +	duty = (1U << PWM_SIFIVE_CMPWIDTH) - 1 - duty;

I find it irritating that both values are assigned to duty. I'd spend
another variable and make this:

	inactive = readl(ddata->regs + PWM_SIFIVE_PWMCMP(pwm->hwpwm));
	duty = (1U << PWM_SIFIVE_CMPWIDTH) - 1 - inactive;


>  
>  	state->enabled = duty > 0;
>  
> @@ -123,11 +124,10 @@ static int pwm_sifive_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
>  	state->period = ddata->real_period;
>  	state->duty_cycle =
>  		(u64)duty * ddata->real_period >> PWM_SIFIVE_CMPWIDTH;
> -	state->polarity = PWM_POLARITY_INVERSED;
> +	state->polarity = PWM_POLARITY_NORMAL;
>  
>  	return 0;
>  }
> -

Please keep this empty line between functions.

>  static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *pwm,
>  			    const struct pwm_state *state)
>  {

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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Re: [PATCH v8 2/3] pwm: sifive: change the PWM controlled LED algorithm

[Nylon Chen]

Uwe Kleine-König <u.kleine-koenig@pengutronix.de> 於 2024年2月6日 週二 上午2:07寫道：
>
> Hello,
Hi Uwe, thanks for your feedback.
>
> Regarding the Subject: The patch has nothing to do with an LED, has it?
I will correct this.
>
> On Fri, Jan 26, 2024 at 03:40:44PM +0800, Nylon Chen wrote:
> > The `frac` variable represents the pulse inactive time, and the result
> > of this algorithm is the pulse active time. Therefore, we must reverse the result.
>
> Please break lines at 75 columns in the commit log.
got it.
>
> > The reference is SiFive FU740-C000 Manual[0]
> >
> > Link: https://sifive.cdn.prismic.io/sifive/1a82e600-1f93-4f41-b2d8-86ed8b16acba_fu740-c000-manual-v1p6.pdf [0]
>
> I looked at Figure 29 in this document (version v1p6, pdf page 148). Not
> sure I understand that correctly, but I expect that the output of the
> ">=?" node below pwmcmp0 to become 1 if pwms has reached pwmcmp0, is
> that right? In that case this output is zero when pwmcount is zero and
> then pwmcmp0ip is zero, too. So a period starts with the inactive part
> and so it's inversed polarity.
>
> What made you think that the current driver implementation is wrong?

This is the process of my speculation.

This is a HiFive Unmatched/Unleashed LED-PWM layout

            VDD
               |
               |
           _____
           \        /   LED
            \     /
              ---
               |
               |
               |
         ______
        |              |
        -             |
        ^    -->    |------ PWM
        |___|___|
               |
               |
              __
               -
            GND

- the waveform
e.g. duty=30s, period=100s, actvie-high = 30%, active-low = 70%

V
^
|
| ----------|
|             |
|             |
|______ |__________ > t

When VCC is high, the LED will be illuminated, which is an active-high
logic. This is why I want to remove "active-low".

For HW, we just focus on pwmcount/pwmcmp[0-3]
- pwmcount default is zero, that counter 0->1->0xffff
- Follow the origin algorithm the frac=0x0(on) / 0xffff(off) and when
the smaller the value of frac, the brighter the light.
   -- E.g. pwmcmp = 0x2, pwmcount 0x0->0x1->...->0xffff
       --- 0->0x2=low & 0x3->0xffff=high => 98%
   -- E.g. pwmcmp = 0xffff, pwmcount 0x0->0x1->...->0xffff
       --- 0->0xffff=low => 0%
- For SW, we reference the algorithm. (D=PW/T*100% D=duty_cycle,
T=period, PW=pulse width (pulse active time))
  -- when we consider HW behavior
  --- Direct writing SW frac into HW's pwmcmp is active low, so when
we want to get an active-high behavior that use a invert function.

If my understanding or deduction process is incorrect, please let me
know. Thank you.
>
> > Co-developed-by: Zong Li <zong.li@sifive.com>
> > Signed-off-by: Zong Li <zong.li@sifive.com>
> > Co-developed-by: Vincent Chen <vincent.chen@sifive.com>
> > Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
> > Signed-off-by: Nylon Chen <nylon.chen@sifive.com>
> > ---
> >  drivers/pwm/pwm-sifive.c | 7 ++++---
> >  1 file changed, 4 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/pwm/pwm-sifive.c b/drivers/pwm/pwm-sifive.c
> > index eabddb7c7820..b07c8598bb21 100644
> > --- a/drivers/pwm/pwm-sifive.c
> > +++ b/drivers/pwm/pwm-sifive.c
> > @@ -113,6 +113,7 @@ static int pwm_sifive_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
> >       u32 duty, val;
> >
> >       duty = readl(ddata->regs + PWM_SIFIVE_PWMCMP(pwm->hwpwm));
> > +     duty = (1U << PWM_SIFIVE_CMPWIDTH) - 1 - duty;
>
> I find it irritating that both values are assigned to duty. I'd spend
> another variable and make this:
>
>         inactive = readl(ddata->regs + PWM_SIFIVE_PWMCMP(pwm->hwpwm));
>         duty = (1U << PWM_SIFIVE_CMPWIDTH) - 1 - inactive;
got it.
>
>
> >
> >       state->enabled = duty > 0;
> >
> > @@ -123,11 +124,10 @@ static int pwm_sifive_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
> >       state->period = ddata->real_period;
> >       state->duty_cycle =
> >               (u64)duty * ddata->real_period >> PWM_SIFIVE_CMPWIDTH;
> > -     state->polarity = PWM_POLARITY_INVERSED;
> > +     state->polarity = PWM_POLARITY_NORMAL;
> >
> >       return 0;
> >  }
> > -
>
> Please keep this empty line between functions.
got it.
>
> >  static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> >                           const struct pwm_state *state)
> >  {
>
> Best regards
> Uwe
>
> --
> Pengutronix e.K.                           | Uwe Kleine-König            |
> Industrial Linux Solutions                 | https://www.pengutronix.de/ |

[PATCH v8 3/3] pwm: sifive: Fix the error in the idempotent test within the pwm_apply_state_debug function

[Nylon Chen]

Round the result to the nearest whole number. This ensures that
real_period is always a reasonable integer that is not lower than the
actual value.

e.g.
$ echo 110 > /sys/devices/platform/led-controller-1/leds/d12/brightness
$ .apply is not idempotent (ena=1 pol=0 1739692/4032985) -> (ena=1 pol=0 1739630/4032985)

Co-developed-by: Zong Li <zong.li@sifive.com>
Signed-off-by: Zong Li <zong.li@sifive.com>
Signed-off-by: Nylon Chen <nylon.chen@sifive.com>
---
 drivers/pwm/pwm-sifive.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pwm/pwm-sifive.c b/drivers/pwm/pwm-sifive.c
index b07c8598bb21..7cf7a76cdb44 100644
--- a/drivers/pwm/pwm-sifive.c
+++ b/drivers/pwm/pwm-sifive.c
@@ -101,7 +101,7 @@ static void pwm_sifive_update_clock(struct pwm_sifive_ddata *ddata,
 
 	/* As scale <= 15 the shift operation cannot overflow. */
 	num = (unsigned long long)NSEC_PER_SEC << (PWM_SIFIVE_CMPWIDTH + scale);
-	ddata->real_period = div64_ul(num, rate);
+	ddata->real_period = DIV_ROUND_UP_ULL(num, rate);
 	dev_dbg(ddata->chip.dev,
 		"New real_period = %u ns\n", ddata->real_period);
 }
-- 
2.42.0