[PATCH] pwm: rockchip: simplify rockchip_pwm_get_state()

[PATCH] pwm: rockchip: simplify rockchip_pwm_get_state()

[Rasmus Villemoes]

The way state->enabled is computed is rather convoluted and hard to
read - both branches of the if() actually do the exact same thing. So
remove the if(), and further simplify "<boolean condition> ? true :
false" to "<boolean condition>".

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
---
I stumbled on this while trying to understand how the pwm subsystem
works. This patch is a semantic no-op, but it's also possible that,
say, the first branch simply contains a "double negative" so either
the != should be == or the "false : true" should be "true : false".

 drivers/pwm/pwm-rockchip.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/drivers/pwm/pwm-rockchip.c b/drivers/pwm/pwm-rockchip.c
index 51b96cb7dd25..54c6399e3f00 100644
--- a/drivers/pwm/pwm-rockchip.c
+++ b/drivers/pwm/pwm-rockchip.c
@@ -83,12 +83,7 @@ static void rockchip_pwm_get_state(struct pwm_chip *chip,
 	state->duty_cycle =  DIV_ROUND_CLOSEST_ULL(tmp, clk_rate);
 
 	val = readl_relaxed(pc->base + pc->data->regs.ctrl);
-	if (pc->data->supports_polarity)
-		state->enabled = ((val & enable_conf) != enable_conf) ?
-				 false : true;
-	else
-		state->enabled = ((val & enable_conf) == enable_conf) ?
-				 true : false;
+	state->enabled = ((val & enable_conf) == enable_conf);
 
 	if (pc->data->supports_polarity) {
 		if (!(val & PWM_DUTY_POSITIVE))
-- 
2.20.1

Re: [PATCH] pwm: rockchip: simplify rockchip_pwm_get_state()

[oUwe Kleine-König]

On Thu, Sep 19, 2019 at 11:17:27AM +0200, Rasmus Villemoes wrote:
> The way state->enabled is computed is rather convoluted and hard to
> read - both branches of the if() actually do the exact same thing. So
> remove the if(), and further simplify "<boolean condition> ? true :
> false" to "<boolean condition>".
> 
> Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
> ---
> I stumbled on this while trying to understand how the pwm subsystem
> works. This patch is a semantic no-op, but it's also possible that,
> say, the first branch simply contains a "double negative" so either
> the != should be == or the "false : true" should be "true : false".

The change looks obviously right, it's a noop.

I share your doubts however. The construct was introduced in commit 
831b2790507b ("pwm: rockchip: Use same PWM ops for each IP") by David
Wu.

Before there were rockchip_pwm_get_state_v1 for the supports_polarity =
false case and rockchip_pwm_get_state_v2 for supports_polarity = true.

In both state->enabled was assigned true if ((val & enable_conf) ==
enable_conf). So I assume everything is fine.

A confirmation by David would be great though.

As a side note: Is there publicly available documentation for this IP?
If a link were added to the driver's header we could check easily
ourselves.

Best regards
Uwe

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

Re: [PATCH] pwm: rockchip: simplify rockchip_pwm_get_state()

[Uwe Kleine-König]

Hello David,

On Thu, Sep 19, 2019 at 01:11:15PM +0200, oUwe Kleine-König wrote:
> On Thu, Sep 19, 2019 at 11:17:27AM +0200, Rasmus Villemoes wrote:
> > The way state->enabled is computed is rather convoluted and hard to
> > read - both branches of the if() actually do the exact same thing. So
> > remove the if(), and further simplify "<boolean condition> ? true :
> > false" to "<boolean condition>".
> > 
> > Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
> > ---
> > I stumbled on this while trying to understand how the pwm subsystem
> > works. This patch is a semantic no-op, but it's also possible that,
> > say, the first branch simply contains a "double negative" so either
> > the != should be == or the "false : true" should be "true : false".
> 
> The change looks obviously right, it's a noop.
> 
> I share your doubts however. The construct was introduced in commit 
> 831b2790507b ("pwm: rockchip: Use same PWM ops for each IP") by David
> Wu.
> 
> Before there were rockchip_pwm_get_state_v1 for the supports_polarity =
> false case and rockchip_pwm_get_state_v2 for supports_polarity = true.
> 
> In both state->enabled was assigned true if ((val & enable_conf) ==
> enable_conf). So I assume everything is fine.
> 
> A confirmation by David would be great though.

This is still open. Can you please have a look at
https://patchwork.ozlabs.org/project/linux-pwm/patch/20190919091728.24756-1-linux@rasmusvillemoes.dk/
and verify it's correct?

Best regards
Uwe

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

Re: [PATCH] pwm: rockchip: simplify rockchip_pwm_get_state()

[Thierry Reding]

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On Thu, Sep 19, 2019 at 11:17:27AM +0200, Rasmus Villemoes wrote:
> The way state->enabled is computed is rather convoluted and hard to
> read - both branches of the if() actually do the exact same thing. So
> remove the if(), and further simplify "<boolean condition> ? true :
> false" to "<boolean condition>".
> 
> Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
> ---
> I stumbled on this while trying to understand how the pwm subsystem
> works. This patch is a semantic no-op, but it's also possible that,
> say, the first branch simply contains a "double negative" so either
> the != should be == or the "false : true" should be "true : false".
> 
>  drivers/pwm/pwm-rockchip.c | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)

I've applied this. Irrespective of any feedback David would have this is
correct and a nice simplification.

Thierry

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Re: [PATCH] pwm: rockchip: simplify rockchip_pwm_get_state()

[David Wu]

This change is very good, thank you. The code continues from the 
original code(get_state_v1 and get_state_v2), didn’t make any changes at 
that time, and sorry I have not seen linux-rockchip@lists.infradead.org 
mail recently.

在 2020/6/2 下午8:39, Thierry Reding 写道:
> On Thu, Sep 19, 2019 at 11:17:27AM +0200, Rasmus Villemoes wrote:
>> The way state->enabled is computed is rather convoluted and hard to
>> read - both branches of the if() actually do the exact same thing. So
>> remove the if(), and further simplify "<boolean condition> ? true :
>> false" to "<boolean condition>".
>>
>> Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
>> ---
>> I stumbled on this while trying to understand how the pwm subsystem
>> works. This patch is a semantic no-op, but it's also possible that,
>> say, the first branch simply contains a "double negative" so either
>> the != should be == or the "false : true" should be "true : false".
>>
>>   drivers/pwm/pwm-rockchip.c | 7 +------
>>   1 file changed, 1 insertion(+), 6 deletions(-)
> 
> I've applied this. Irrespective of any feedback David would have this is
> correct and a nice simplification.
> 
> Thierry
>