[PATCH 1/2] dt-bindings: leds: register-bit-led: Add value property

[PATCH 1/2] dt-bindings: leds: register-bit-led: Add value property

[Pali Rohár]

Allow to define inverted logic (0 - enable LED, 1 - disable LED) via value
property. This property name is already used by other syscon drivers, e.g.
syscon-reboot.

Signed-off-by: Pali Rohár <pali@kernel.org>
---
 .../devicetree/bindings/leds/register-bit-led.yaml    | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/Documentation/devicetree/bindings/leds/register-bit-led.yaml b/Documentation/devicetree/bindings/leds/register-bit-led.yaml
index 79b8fc0f9d23..d6054a3f9087 100644
--- a/Documentation/devicetree/bindings/leds/register-bit-led.yaml
+++ b/Documentation/devicetree/bindings/leds/register-bit-led.yaml
@@ -43,6 +43,17 @@ properties:
         0x100000, 0x200000, 0x400000, 0x800000, 0x1000000, 0x2000000, 0x4000000,
         0x8000000, 0x10000000, 0x20000000, 0x40000000, 0x80000000 ]
 
+  value:
+    description:
+      bit value of ON state for the bit controlling this LED in the register
+      when not specified it is same as the mask
+    $ref: /schemas/types.yaml#/definitions/uint32
+    enum:
+      [ 0x0, 0x1, 0x2, 0x4, 0x8, 0x10, 0x20, 0x40, 0x80, 0x100, 0x200, 0x400, 0x800,
+        0x1000, 0x2000, 0x4000, 0x8000, 0x10000, 0x20000, 0x40000, 0x80000,
+        0x100000, 0x200000, 0x400000, 0x800000, 0x1000000, 0x2000000, 0x4000000,
+        0x8000000, 0x10000000, 0x20000000, 0x40000000, 0x80000000 ]
+
   offset:
     description:
       register offset to the register controlling this LED
-- 
2.20.1

[PATCH 2/2] leds: syscon: Implement support for value property

[Pali Rohár]

This new value property specify when is LED enabled. By default its value
is from the mask and therefore LED is enabled when bit is set. This change
allows to define inverted logic (0 - enable LED, 1 - disable LED) by
setting value property to zero.

Signed-off-by: Pali Rohár <pali@kernel.org>
---
 drivers/leds/leds-syscon.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/leds/leds-syscon.c b/drivers/leds/leds-syscon.c
index 7eddb8ecb44e..337a0bada967 100644
--- a/drivers/leds/leds-syscon.c
+++ b/drivers/leds/leds-syscon.c
@@ -29,6 +29,7 @@ struct syscon_led {
 	struct regmap *map;
 	u32 offset;
 	u32 mask;
+	u32 value;
 	bool state;
 };
 
@@ -41,10 +42,10 @@ static void syscon_led_set(struct led_classdev *led_cdev,
 	int ret;
 
 	if (value == LED_OFF) {
-		val = 0;
+		val = ~sled->value;
 		sled->state = false;
 	} else {
-		val = sled->mask;
+		val = sled->value;
 		sled->state = true;
 	}
 
@@ -85,6 +86,8 @@ static int syscon_led_probe(struct platform_device *pdev)
 		return -EINVAL;
 	if (of_property_read_u32(np, "mask", &sled->mask))
 		return -EINVAL;
+	if (of_property_read_u32(np, "value", &sled->value))
+		sled->value = sled->mask;
 
 	state = of_get_property(np, "default-state", NULL);
 	if (state) {
@@ -94,18 +97,19 @@ static int syscon_led_probe(struct platform_device *pdev)
 			ret = regmap_read(map, sled->offset, &val);
 			if (ret < 0)
 				return ret;
-			sled->state = !!(val & sled->mask);
+			sled->state = (val & sled->mask) == sled->value;
 		} else if (!strcmp(state, "on")) {
 			sled->state = true;
 			ret = regmap_update_bits(map, sled->offset,
 						 sled->mask,
-						 sled->mask);
+						 sled->value);
 			if (ret < 0)
 				return ret;
 		} else {
 			sled->state = false;
 			ret = regmap_update_bits(map, sled->offset,
-						 sled->mask, 0);
+						 sled->mask,
+						 ~sled->value);
 			if (ret < 0)
 				return ret;
 		}
-- 
2.20.1

Re: [PATCH 1/2] dt-bindings: leds: register-bit-led: Add value property

[Rob Herring]

On Wed, Jul 06, 2022 at 01:28:27PM +0200, Pali Rohár wrote:
> Allow to define inverted logic (0 - enable LED, 1 - disable LED) via value
> property. This property name is already used by other syscon drivers, e.g.
> syscon-reboot.

Yes, but those are potentially multi-bit values. This is a single bit 
value, and the only value that's ever needed is 0. Why not just use 
'active-low' here?

> 
> Signed-off-by: Pali Rohár <pali@kernel.org>
> ---
>  .../devicetree/bindings/leds/register-bit-led.yaml    | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/leds/register-bit-led.yaml b/Documentation/devicetree/bindings/leds/register-bit-led.yaml
> index 79b8fc0f9d23..d6054a3f9087 100644
> --- a/Documentation/devicetree/bindings/leds/register-bit-led.yaml
> +++ b/Documentation/devicetree/bindings/leds/register-bit-led.yaml
> @@ -43,6 +43,17 @@ properties:
>          0x100000, 0x200000, 0x400000, 0x800000, 0x1000000, 0x2000000, 0x4000000,
>          0x8000000, 0x10000000, 0x20000000, 0x40000000, 0x80000000 ]
>  
> +  value:
> +    description:
> +      bit value of ON state for the bit controlling this LED in the register
> +      when not specified it is same as the mask
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    enum:
> +      [ 0x0, 0x1, 0x2, 0x4, 0x8, 0x10, 0x20, 0x40, 0x80, 0x100, 0x200, 0x400, 0x800,
> +        0x1000, 0x2000, 0x4000, 0x8000, 0x10000, 0x20000, 0x40000, 0x80000,
> +        0x100000, 0x200000, 0x400000, 0x800000, 0x1000000, 0x2000000, 0x4000000,
> +        0x8000000, 0x10000000, 0x20000000, 0x40000000, 0x80000000 ]
> +
>    offset:
>      description:
>        register offset to the register controlling this LED
> -- 
> 2.20.1
> 
> 

Re: [PATCH 1/2] dt-bindings: leds: register-bit-led: Add value property

[Pali Rohár]

On Wednesday 06 July 2022 10:21:11 Rob Herring wrote:
> On Wed, Jul 06, 2022 at 01:28:27PM +0200, Pali Rohár wrote:
> > Allow to define inverted logic (0 - enable LED, 1 - disable LED) via value
> > property. This property name is already used by other syscon drivers, e.g.
> > syscon-reboot.
> 
> Yes, but those are potentially multi-bit values. This is a single bit 
> value, and the only value that's ever needed is 0. Why not just use 
> 'active-low' here?

Just because to have uniform definitions across more syscon nodes.

> > 
> > Signed-off-by: Pali Rohár <pali@kernel.org>
> > ---
> >  .../devicetree/bindings/leds/register-bit-led.yaml    | 11 +++++++++++
> >  1 file changed, 11 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/leds/register-bit-led.yaml b/Documentation/devicetree/bindings/leds/register-bit-led.yaml
> > index 79b8fc0f9d23..d6054a3f9087 100644
> > --- a/Documentation/devicetree/bindings/leds/register-bit-led.yaml
> > +++ b/Documentation/devicetree/bindings/leds/register-bit-led.yaml
> > @@ -43,6 +43,17 @@ properties:
> >          0x100000, 0x200000, 0x400000, 0x800000, 0x1000000, 0x2000000, 0x4000000,
> >          0x8000000, 0x10000000, 0x20000000, 0x40000000, 0x80000000 ]
> >  
> > +  value:
> > +    description:
> > +      bit value of ON state for the bit controlling this LED in the register
> > +      when not specified it is same as the mask
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +    enum:
> > +      [ 0x0, 0x1, 0x2, 0x4, 0x8, 0x10, 0x20, 0x40, 0x80, 0x100, 0x200, 0x400, 0x800,
> > +        0x1000, 0x2000, 0x4000, 0x8000, 0x10000, 0x20000, 0x40000, 0x80000,
> > +        0x100000, 0x200000, 0x400000, 0x800000, 0x1000000, 0x2000000, 0x4000000,
> > +        0x8000000, 0x10000000, 0x20000000, 0x40000000, 0x80000000 ]
> > +
> >    offset:
> >      description:
> >        register offset to the register controlling this LED
> > -- 
> > 2.20.1
> > 
> > 

Re: [PATCH 1/2] dt-bindings: leds: register-bit-led: Add value property

[Linus Walleij]

On Wed, Jul 6, 2022 at 6:23 PM Pali Rohár <pali@kernel.org> wrote:
> On Wednesday 06 July 2022 10:21:11 Rob Herring wrote:
> > On Wed, Jul 06, 2022 at 01:28:27PM +0200, Pali Rohár wrote:
> > > Allow to define inverted logic (0 - enable LED, 1 - disable LED) via value
> > > property. This property name is already used by other syscon drivers, e.g.
> > > syscon-reboot.
> >
> > Yes, but those are potentially multi-bit values. This is a single bit
> > value, and the only value that's ever needed is 0. Why not just use
> > 'active-low' here?
>
> Just because to have uniform definitions across more syscon nodes.

But what happens if he mask and value don't line up?

mask = 0x10;
value = 0x08;

If you just state active-low; this kind of mistake is not possible to make.

So I'd rather go for active-low;

Yours,
Linus Walleij

Re: [PATCH 1/2] dt-bindings: leds: register-bit-led: Add value property

[Pali Rohár]

On Monday 11 July 2022 14:06:50 Linus Walleij wrote:
> On Wed, Jul 6, 2022 at 6:23 PM Pali Rohár <pali@kernel.org> wrote:
> > On Wednesday 06 July 2022 10:21:11 Rob Herring wrote:
> > > On Wed, Jul 06, 2022 at 01:28:27PM +0200, Pali Rohár wrote:
> > > > Allow to define inverted logic (0 - enable LED, 1 - disable LED) via value
> > > > property. This property name is already used by other syscon drivers, e.g.
> > > > syscon-reboot.
> > >
> > > Yes, but those are potentially multi-bit values. This is a single bit
> > > value, and the only value that's ever needed is 0. Why not just use
> > > 'active-low' here?
> >
> > Just because to have uniform definitions across more syscon nodes.
> 
> But what happens if he mask and value don't line up?
> 
> mask = 0x10;
> value = 0x08;

Same what would happen in other drivers, no?

Only those value bits are take into account which are also sets in the mask.

> If you just state active-low; this kind of mistake is not possible to make.
> 
> So I'd rather go for active-low;
> 
> Yours,
> Linus Walleij

Re: [PATCH 1/2] dt-bindings: leds: register-bit-led: Add value property

[Linus Walleij]

On Mon, Jul 11, 2022 at 2:10 PM Pali Rohár <pali@kernel.org> wrote:
> On Monday 11 July 2022 14:06:50 Linus Walleij wrote:
> > On Wed, Jul 6, 2022 at 6:23 PM Pali Rohár <pali@kernel.org> wrote:
> > > On Wednesday 06 July 2022 10:21:11 Rob Herring wrote:
> > > > On Wed, Jul 06, 2022 at 01:28:27PM +0200, Pali Rohár wrote:
> > > > > Allow to define inverted logic (0 - enable LED, 1 - disable LED) via value
> > > > > property. This property name is already used by other syscon drivers, e.g.
> > > > > syscon-reboot.
> > > >
> > > > Yes, but those are potentially multi-bit values. This is a single bit
> > > > value, and the only value that's ever needed is 0. Why not just use
> > > > 'active-low' here?
> > >
> > > Just because to have uniform definitions across more syscon nodes.
> >
> > But what happens if he mask and value don't line up?
> >
> > mask = 0x10;
> > value = 0x08;
>
> Same what would happen in other drivers, no?
>
> Only those value bits are take into account which are also sets in the mask.

Two wrongs does not make one right. I.e. just because this bad
pattern is used in other syscon drivers we do not need to repeat their
mistakes. Also, in this case we can only specify one bit due to the
way the enum is designed, other drivers may specify multiple bits.

This also becomes a bit confusing:

+    enum:
+      [ 0x0,

What you do is add 0 at the beginning of the enum but that represent
a low bit of any from 0-31. I just get confused, active-low is crystal clear.

Yours,
Linus Walleij