[PATCH 0/2] Add the property to make ocp level selectable

[PATCH 0/2] Add the property to make ocp level selectable

[cy_huang]

From: ChiYuan Huang <cy_huang@richtek.com>

This patch series is to make ocp level selectable.

Some application design use small inductor. And it's easy to trigger the
over current protection. Due to the OCP limit, It make the brightness current
not match the configured value.

To meet the HW design, the ocp level have to be selectable.

ChiYuan Huang (2):
  dt-bindings: backlight: rt4831: Add the new property for ocp level
    selection
  backlight: rt4831: Add the property parsing for ocp level selection

 .../bindings/leds/backlight/richtek,rt4831-backlight.yaml   |  8 ++++++++
 drivers/video/backlight/rt4831-backlight.c                  | 13 +++++++++++++
 include/dt-bindings/leds/rt4831-backlight.h                 |  5 +++++
 3 files changed, 26 insertions(+)

-- 
2.7.4

[PATCH 1/2] dt-bindings: backlight: rt4831: Add the new property for ocp level selection

[cy_huang]

From: ChiYuan Huang <cy_huang@richtek.com>

Add the new property for ocp level selection.

Signed-off-by: ChiYuan Huang <cy_huang@richtek.com>
---
 .../bindings/leds/backlight/richtek,rt4831-backlight.yaml         | 8 ++++++++
 include/dt-bindings/leds/rt4831-backlight.h                       | 5 +++++
 2 files changed, 13 insertions(+)

diff --git a/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml b/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml
index e0ac686..c1c59de 100644
--- a/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml
+++ b/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml
@@ -47,6 +47,14 @@ properties:
     minimum: 0
     maximum: 3
 
+  richtek,bled-ocp-sel:
+    description: |
+      Backlight OCP level selection, currently support 0.9A/1.2A/1.5A/1.8A
+    $ref: /schemas/types.yaml#/definitions/uint8
+    default: 1
+    minimum: 0
+    maximum: 3
+
   richtek,channel-use:
     description: |
       Backlight LED channel to be used.
diff --git a/include/dt-bindings/leds/rt4831-backlight.h b/include/dt-bindings/leds/rt4831-backlight.h
index 125c635..e8b8609 100644
--- a/include/dt-bindings/leds/rt4831-backlight.h
+++ b/include/dt-bindings/leds/rt4831-backlight.h
@@ -14,6 +14,11 @@
 #define RT4831_BLOVPLVL_25V	2
 #define RT4831_BLOVPLVL_29V	3
 
+#define RT4831_BLOCPLVL_0P9A	0
+#define RT4831_BLOCPLVL_1P2A	1
+#define RT4831_BLOCPLVL_1P5A	2
+#define RT4831_BLOCPLVL_1P8A	3
+
 #define RT4831_BLED_CH1EN	(1 << 0)
 #define RT4831_BLED_CH2EN	(1 << 1)
 #define RT4831_BLED_CH3EN	(1 << 2)
-- 
2.7.4

[PATCH 2/2] backlight: rt4831: Add the property parsing for ocp level selection

[cy_huang]

From: ChiYuan Huang <cy_huang@richtek.com>

Add the property parsing for ocp level selection.

Reported-by: Lucas Tsai <lucas_tsai@richtek.com>
Signed-off-by: ChiYuan Huang <cy_huang@richtek.com>
---
 drivers/video/backlight/rt4831-backlight.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/video/backlight/rt4831-backlight.c b/drivers/video/backlight/rt4831-backlight.c
index 42155c7..c81f7d9 100644
--- a/drivers/video/backlight/rt4831-backlight.c
+++ b/drivers/video/backlight/rt4831-backlight.c
@@ -12,6 +12,7 @@
 #define RT4831_REG_BLCFG	0x02
 #define RT4831_REG_BLDIML	0x04
 #define RT4831_REG_ENABLE	0x08
+#define RT4831_REG_BLOPT2	0x11
 
 #define RT4831_BLMAX_BRIGHTNESS	2048
 
@@ -23,6 +24,8 @@
 #define RT4831_BLDIML_MASK	GENMASK(2, 0)
 #define RT4831_BLDIMH_MASK	GENMASK(10, 3)
 #define RT4831_BLDIMH_SHIFT	3
+#define RT4831_BLOCP_MASK	GENMASK(1, 0)
+#define RT4831_BLOCP_SHIFT	0
 
 struct rt4831_priv {
 	struct device *dev;
@@ -120,6 +123,16 @@ static int rt4831_parse_backlight_properties(struct rt4831_priv *priv,
 	if (ret)
 		return ret;
 
+	ret = device_property_read_u8(dev, "richtek,bled-ocp-sel", &propval);
+	if (ret)
+		propval = RT4831_BLOCPLVL_1P2A;
+
+	propval = min_t(u8, propval, RT4831_BLOCPLVL_1P8A);
+	ret = regmap_update_bits(priv->regmap, RT4831_REG_BLOPT2, RT4831_BLOCP_MASK,
+				 propval << RT4831_BLOCP_SHIFT);
+	if (ret)
+		return ret;
+
 	ret = device_property_read_u8(dev, "richtek,channel-use", &propval);
 	if (ret) {
 		dev_err(dev, "richtek,channel-use DT property missing\n");
-- 
2.7.4

Re: [PATCH 1/2] dt-bindings: backlight: rt4831: Add the new property for ocp level selection

[Krzysztof Kozlowski]

On 26/05/2022 05:16, cy_huang wrote:
> From: ChiYuan Huang <cy_huang@richtek.com>
> 
> Add the new property for ocp level selection.
> 
> Signed-off-by: ChiYuan Huang <cy_huang@richtek.com>
> ---
>  .../bindings/leds/backlight/richtek,rt4831-backlight.yaml         | 8 ++++++++
>  include/dt-bindings/leds/rt4831-backlight.h                       | 5 +++++
>  2 files changed, 13 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml b/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml
> index e0ac686..c1c59de 100644
> --- a/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml
> +++ b/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml
> @@ -47,6 +47,14 @@ properties:
>      minimum: 0
>      maximum: 3
>  
> +  richtek,bled-ocp-sel:

Skip "sel" as it is a shortcut of selection. Name instead:
"richtek,backlight-ocp"


> +    description: |
> +      Backlight OCP level selection, currently support 0.9A/1.2A/1.5A/1.8A

Could you explain here what is OCP (unfold the acronym)?


Best regards,
Krzysztof

Re: [PATCH 1/2] dt-bindings: backlight: rt4831: Add the new property for ocp level selection

[ChiYuan Huang]

Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> 於 2022年5月26日 週四 下午4:06寫道：
>
> On 26/05/2022 05:16, cy_huang wrote:
> > From: ChiYuan Huang <cy_huang@richtek.com>
> >
> > Add the new property for ocp level selection.
> >
> > Signed-off-by: ChiYuan Huang <cy_huang@richtek.com>
> > ---
> >  .../bindings/leds/backlight/richtek,rt4831-backlight.yaml         | 8 ++++++++
> >  include/dt-bindings/leds/rt4831-backlight.h                       | 5 +++++
> >  2 files changed, 13 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml b/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml
> > index e0ac686..c1c59de 100644
> > --- a/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml
> > +++ b/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml
> > @@ -47,6 +47,14 @@ properties:
> >      minimum: 0
> >      maximum: 3
> >
> > +  richtek,bled-ocp-sel:
>
> Skip "sel" as it is a shortcut of selection. Name instead:
> "richtek,backlight-ocp"
>
OK, if so, do I need to rename all properties from 'bled' to 'backlight' ?
If  only this property is naming as 'backlight'. it may conflict with
the others like as "richtek,bled-ovp-sel".
>
> > +    description: |
> > +      Backlight OCP level selection, currently support 0.9A/1.2A/1.5A/1.8A
>
> Could you explain here what is OCP (unfold the acronym)?
Yes. And the full name is 'over current protection'.
>
>
> Best regards,
> Krzysztof

Re: [PATCH 2/2] backlight: rt4831: Add the property parsing for ocp level selection

[Daniel Thompson]

On Thu, May 26, 2022 at 11:16:35AM +0800, cy_huang wrote:
> From: ChiYuan Huang <cy_huang@richtek.com>
> 
> Add the property parsing for ocp level selection.

Isn't this just restating the Subject: line?

It would be better to provide information useful to the reviewer here.
Something like:

"Currently this driver simply inherits whatever over-current protection
level is programmed into the hardware when it is handed over. Typically
this will be the reset value, <whatever>A, although the bootloader could
have established a different value.

Allow the correct OCP value to be provided by the DT."

BTW please don't uncritically copy the above into the patch header. It is
just made something up as an example and I did no fact checking...


> 
> Reported-by: Lucas Tsai <lucas_tsai@richtek.com>
> Signed-off-by: ChiYuan Huang <cy_huang@richtek.com>
> ---
>  drivers/video/backlight/rt4831-backlight.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/drivers/video/backlight/rt4831-backlight.c b/drivers/video/backlight/rt4831-backlight.c
> index 42155c7..c81f7d9 100644
> --- a/drivers/video/backlight/rt4831-backlight.c
> +++ b/drivers/video/backlight/rt4831-backlight.c
> @@ -12,6 +12,7 @@
>  #define RT4831_REG_BLCFG	0x02
>  #define RT4831_REG_BLDIML	0x04
>  #define RT4831_REG_ENABLE	0x08
> +#define RT4831_REG_BLOPT2	0x11
>  
>  #define RT4831_BLMAX_BRIGHTNESS	2048
>  
> @@ -23,6 +24,8 @@
>  #define RT4831_BLDIML_MASK	GENMASK(2, 0)
>  #define RT4831_BLDIMH_MASK	GENMASK(10, 3)
>  #define RT4831_BLDIMH_SHIFT	3
> +#define RT4831_BLOCP_MASK	GENMASK(1, 0)
> +#define RT4831_BLOCP_SHIFT	0
>  
>  struct rt4831_priv {
>  	struct device *dev;
> @@ -120,6 +123,16 @@ static int rt4831_parse_backlight_properties(struct rt4831_priv *priv,
>  	if (ret)
>  		return ret;
>  
> +	ret = device_property_read_u8(dev, "richtek,bled-ocp-sel", &propval);
> +	if (ret)
> +		propval = RT4831_BLOCPLVL_1P2A;

Is 1.2A the reset value for the register?

Additionally, it looks like adding a hard-coded default would cause
problems for existing platforms where the bootloader doesn't use
richtek,bled-ocp-sel and pre-configures a different value itself.

Would it be safer (in terms of working nicely with older bootloaders)
to only write to the RT4831_BLOCP_MASK if the new property is set?


Daniel.



> +
> +	propval = min_t(u8, propval, RT4831_BLOCPLVL_1P8A);
> +	ret = regmap_update_bits(priv->regmap, RT4831_REG_BLOPT2, RT4831_BLOCP_MASK,
> +				 propval << RT4831_BLOCP_SHIFT);
> +	if (ret)
> +		return ret;
> +
>  	ret = device_property_read_u8(dev, "richtek,channel-use", &propval);
>  	if (ret) {
>  		dev_err(dev, "richtek,channel-use DT property missing\n");
> -- 
> 2.7.4
> 

Re: [PATCH 1/2] dt-bindings: backlight: rt4831: Add the new property for ocp level selection

[Krzysztof Kozlowski]

On 26/05/2022 10:13, ChiYuan Huang wrote:
> Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> 於 2022年5月26日 週四 下午4:06寫道：
>>
>> On 26/05/2022 05:16, cy_huang wrote:
>>> From: ChiYuan Huang <cy_huang@richtek.com>
>>>
>>> Add the new property for ocp level selection.
>>>
>>> Signed-off-by: ChiYuan Huang <cy_huang@richtek.com>
>>> ---
>>>  .../bindings/leds/backlight/richtek,rt4831-backlight.yaml         | 8 ++++++++
>>>  include/dt-bindings/leds/rt4831-backlight.h                       | 5 +++++
>>>  2 files changed, 13 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml b/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml
>>> index e0ac686..c1c59de 100644
>>> --- a/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml
>>> +++ b/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml
>>> @@ -47,6 +47,14 @@ properties:
>>>      minimum: 0
>>>      maximum: 3
>>>
>>> +  richtek,bled-ocp-sel:
>>
>> Skip "sel" as it is a shortcut of selection. Name instead:
>> "richtek,backlight-ocp"
>>
> OK, if so, do I need to rename all properties from 'bled' to 'backlight' ?
> If  only this property is naming as 'backlight'. it may conflict with
> the others like as "richtek,bled-ovp-sel".

Ah, no, no need.

>>
>>> +    description: |
>>> +      Backlight OCP level selection, currently support 0.9A/1.2A/1.5A/1.8A
>>
>> Could you explain here what is OCP (unfold the acronym)?
> Yes. And the full name is 'over current protection'.

Thanks and this leads to second thing - you encode register value
instead of logical value. This must be a logical value in mA, so
"richtek,bled-ocp-microamp".

I see you already did some register-style for voltage. It's wrong but it
was done, so let it be. But let's don't make that a pattern...


>>
>>
>> Best regards,
>> Krzysztof


Best regards,
Krzysztof

Re: [PATCH 2/2] backlight: rt4831: Add the property parsing for ocp level selection

[ChiYuan Huang]

Daniel Thompson <daniel.thompson@linaro.org> 於 2022年5月26日 週四 下午6:05寫道：
>
> On Thu, May 26, 2022 at 11:16:35AM +0800, cy_huang wrote:
> > From: ChiYuan Huang <cy_huang@richtek.com>
> >
> > Add the property parsing for ocp level selection.
>
> Isn't this just restating the Subject: line?
>
Ah, that's my fault. I didn't state too much in the patch comment.
I only left it in the cover letter.

> It would be better to provide information useful to the reviewer here.
> Something like:
>
> "Currently this driver simply inherits whatever over-current protection
> level is programmed into the hardware when it is handed over. Typically
> this will be the reset value, <whatever>A, although the bootloader could
> have established a different value.
>
> Allow the correct OCP value to be provided by the DT."
>
> BTW please don't uncritically copy the above into the patch header. It is
> just made something up as an example and I did no fact checking...
>
OK, got it.
>
> >
> > Reported-by: Lucas Tsai <lucas_tsai@richtek.com>
> > Signed-off-by: ChiYuan Huang <cy_huang@richtek.com>
> > ---
> >  drivers/video/backlight/rt4831-backlight.c | 13 +++++++++++++
> >  1 file changed, 13 insertions(+)
> >
> > diff --git a/drivers/video/backlight/rt4831-backlight.c b/drivers/video/backlight/rt4831-backlight.c
> > index 42155c7..c81f7d9 100644
> > --- a/drivers/video/backlight/rt4831-backlight.c
> > +++ b/drivers/video/backlight/rt4831-backlight.c
> > @@ -12,6 +12,7 @@
> >  #define RT4831_REG_BLCFG     0x02
> >  #define RT4831_REG_BLDIML    0x04
> >  #define RT4831_REG_ENABLE    0x08
> > +#define RT4831_REG_BLOPT2    0x11
> >
> >  #define RT4831_BLMAX_BRIGHTNESS      2048
> >
> > @@ -23,6 +24,8 @@
> >  #define RT4831_BLDIML_MASK   GENMASK(2, 0)
> >  #define RT4831_BLDIMH_MASK   GENMASK(10, 3)
> >  #define RT4831_BLDIMH_SHIFT  3
> > +#define RT4831_BLOCP_MASK    GENMASK(1, 0)
> > +#define RT4831_BLOCP_SHIFT   0
> >
> >  struct rt4831_priv {
> >       struct device *dev;
> > @@ -120,6 +123,16 @@ static int rt4831_parse_backlight_properties(struct rt4831_priv *priv,
> >       if (ret)
> >               return ret;
> >
> > +     ret = device_property_read_u8(dev, "richtek,bled-ocp-sel", &propval);
> > +     if (ret)
> > +             propval = RT4831_BLOCPLVL_1P2A;
>
> Is 1.2A the reset value for the register?
Yes, it's the HW default value.
>
> Additionally, it looks like adding a hard-coded default would cause
> problems for existing platforms where the bootloader doesn't use
> richtek,bled-ocp-sel and pre-configures a different value itself.
>
> Would it be safer (in terms of working nicely with older bootloaders)
> to only write to the RT4831_BLOCP_MASK if the new property is set?
>
Ah, my excuse. I really didn't consider the case that you mentioned.
It seems it's better to do the judgement here for two cases.
1) property not exist, keep the current HW value
2) property exist, clamp align and update the suitable selector to HW.

Thanks.
>
> Daniel.
>
>
>
> > +
> > +     propval = min_t(u8, propval, RT4831_BLOCPLVL_1P8A);
> > +     ret = regmap_update_bits(priv->regmap, RT4831_REG_BLOPT2, RT4831_BLOCP_MASK,
> > +                              propval << RT4831_BLOCP_SHIFT);
> > +     if (ret)
> > +             return ret;
> > +
> >       ret = device_property_read_u8(dev, "richtek,channel-use", &propval);
> >       if (ret) {
> >               dev_err(dev, "richtek,channel-use DT property missing\n");
> > --
> > 2.7.4
> >

Re: [PATCH 2/2] backlight: rt4831: Add the property parsing for ocp level selection

[Daniel Thompson]

On Fri, May 27, 2022 at 10:24:42AM +0800, ChiYuan Huang wrote:
> Daniel Thompson <daniel.thompson@linaro.org> 於 2022年5月26日 週四 下午6:05寫道：
> >
> > On Thu, May 26, 2022 at 11:16:35AM +0800, cy_huang wrote:
> > > From: ChiYuan Huang <cy_huang@richtek.com>
> > >
> > > Add the property parsing for ocp level selection.
> >
> > Isn't this just restating the Subject: line?
> >
> Ah, that's my fault. I didn't state too much in the patch comment.
> I only left it in the cover letter.
> 
> > It would be better to provide information useful to the reviewer here.
> > Something like:
> >
> > "Currently this driver simply inherits whatever over-current protection
> > level is programmed into the hardware when it is handed over. Typically
> > this will be the reset value, <whatever>A, although the bootloader could
> > have established a different value.
> >
> > Allow the correct OCP value to be provided by the DT."
> >
> > BTW please don't uncritically copy the above into the patch header. It is
> > just made something up as an example and I did no fact checking...
> >
> OK, got it.
> >
> > >
> > > Reported-by: Lucas Tsai <lucas_tsai@richtek.com>
> > > Signed-off-by: ChiYuan Huang <cy_huang@richtek.com>
> > > ---
> > >  drivers/video/backlight/rt4831-backlight.c | 13 +++++++++++++
> > >  1 file changed, 13 insertions(+)
> > >
> > > diff --git a/drivers/video/backlight/rt4831-backlight.c b/drivers/video/backlight/rt4831-backlight.c
> > > index 42155c7..c81f7d9 100644
> > > --- a/drivers/video/backlight/rt4831-backlight.c
> > > +++ b/drivers/video/backlight/rt4831-backlight.c
> > > @@ -12,6 +12,7 @@
> > >  #define RT4831_REG_BLCFG     0x02
> > >  #define RT4831_REG_BLDIML    0x04
> > >  #define RT4831_REG_ENABLE    0x08
> > > +#define RT4831_REG_BLOPT2    0x11
> > >
> > >  #define RT4831_BLMAX_BRIGHTNESS      2048
> > >
> > > @@ -23,6 +24,8 @@
> > >  #define RT4831_BLDIML_MASK   GENMASK(2, 0)
> > >  #define RT4831_BLDIMH_MASK   GENMASK(10, 3)
> > >  #define RT4831_BLDIMH_SHIFT  3
> > > +#define RT4831_BLOCP_MASK    GENMASK(1, 0)
> > > +#define RT4831_BLOCP_SHIFT   0
> > >
> > >  struct rt4831_priv {
> > >       struct device *dev;
> > > @@ -120,6 +123,16 @@ static int rt4831_parse_backlight_properties(struct rt4831_priv *priv,
> > >       if (ret)
> > >               return ret;
> > >
> > > +     ret = device_property_read_u8(dev, "richtek,bled-ocp-sel", &propval);
> > > +     if (ret)
> > > +             propval = RT4831_BLOCPLVL_1P2A;
> >
> > Is 1.2A the reset value for the register?
> Yes, it's the HW default value.
> >
> > Additionally, it looks like adding a hard-coded default would cause
> > problems for existing platforms where the bootloader doesn't use
> > richtek,bled-ocp-sel and pre-configures a different value itself.
> >
> > Would it be safer (in terms of working nicely with older bootloaders)
> > to only write to the RT4831_BLOCP_MASK if the new property is set?
> >
> Ah, my excuse. I really didn't consider the case that you mentioned.
> It seems it's better to do the judgement here for two cases.
> 1) property not exist, keep the current HW value
> 2) property exist, clamp align and update the suitable selector to HW.

Ok, great.

When you make this change can you make sure there is a comment in the
source code explaining that concerns about older firmware is *why* we
treat bled-ocp-sel differently to bled-ovp-sel!


Thanks

Daniel.

Re: [PATCH 1/2] dt-bindings: backlight: rt4831: Add the new property for ocp level selection

[Rob Herring]

On Thu, May 26, 2022 at 12:32:12PM +0200, Krzysztof Kozlowski wrote:
> On 26/05/2022 10:13, ChiYuan Huang wrote:
> > Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> 於 2022年5月26日 週四 下午4:06寫道：
> >>
> >> On 26/05/2022 05:16, cy_huang wrote:
> >>> From: ChiYuan Huang <cy_huang@richtek.com>
> >>>
> >>> Add the new property for ocp level selection.
> >>>
> >>> Signed-off-by: ChiYuan Huang <cy_huang@richtek.com>
> >>> ---
> >>>  .../bindings/leds/backlight/richtek,rt4831-backlight.yaml         | 8 ++++++++
> >>>  include/dt-bindings/leds/rt4831-backlight.h                       | 5 +++++
> >>>  2 files changed, 13 insertions(+)
> >>>
> >>> diff --git a/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml b/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml
> >>> index e0ac686..c1c59de 100644
> >>> --- a/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml
> >>> +++ b/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml
> >>> @@ -47,6 +47,14 @@ properties:
> >>>      minimum: 0
> >>>      maximum: 3
> >>>
> >>> +  richtek,bled-ocp-sel:
> >>
> >> Skip "sel" as it is a shortcut of selection. Name instead:
> >> "richtek,backlight-ocp"
> >>
> > OK, if so, do I need to rename all properties from 'bled' to 'backlight' ?
> > If  only this property is naming as 'backlight'. it may conflict with
> > the others like as "richtek,bled-ovp-sel".
> 
> Ah, no, no need.
> 
> >>
> >>> +    description: |
> >>> +      Backlight OCP level selection, currently support 0.9A/1.2A/1.5A/1.8A
> >>
> >> Could you explain here what is OCP (unfold the acronym)?
> > Yes. And the full name is 'over current protection'.
> 
> Thanks and this leads to second thing - you encode register value
> instead of logical value. This must be a logical value in mA, so
> "richtek,bled-ocp-microamp".

We already have common properties for setting current of LEDs. We should 
use that here I think.

Rob

Re: [PATCH 1/2] dt-bindings: backlight: rt4831: Add the new property for ocp level selection

[Krzysztof Kozlowski]

On 02/06/2022 15:56, Rob Herring wrote:
> On Thu, May 26, 2022 at 12:32:12PM +0200, Krzysztof Kozlowski wrote:
>> On 26/05/2022 10:13, ChiYuan Huang wrote:
>>> Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> 於 2022年5月26日 週四 下午4:06寫道：
>>>>
>>>> On 26/05/2022 05:16, cy_huang wrote:
>>>>> From: ChiYuan Huang <cy_huang@richtek.com>
>>>>>
>>>>> Add the new property for ocp level selection.
>>>>>
>>>>> Signed-off-by: ChiYuan Huang <cy_huang@richtek.com>
>>>>> ---
>>>>>  .../bindings/leds/backlight/richtek,rt4831-backlight.yaml         | 8 ++++++++
>>>>>  include/dt-bindings/leds/rt4831-backlight.h                       | 5 +++++
>>>>>  2 files changed, 13 insertions(+)
>>>>>
>>>>> diff --git a/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml b/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml
>>>>> index e0ac686..c1c59de 100644
>>>>> --- a/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml
>>>>> +++ b/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml
>>>>> @@ -47,6 +47,14 @@ properties:
>>>>>      minimum: 0
>>>>>      maximum: 3
>>>>>
>>>>> +  richtek,bled-ocp-sel:
>>>>
>>>> Skip "sel" as it is a shortcut of selection. Name instead:
>>>> "richtek,backlight-ocp"
>>>>
>>> OK, if so, do I need to rename all properties from 'bled' to 'backlight' ?
>>> If  only this property is naming as 'backlight'. it may conflict with
>>> the others like as "richtek,bled-ovp-sel".
>>
>> Ah, no, no need.
>>
>>>>
>>>>> +    description: |
>>>>> +      Backlight OCP level selection, currently support 0.9A/1.2A/1.5A/1.8A
>>>>
>>>> Could you explain here what is OCP (unfold the acronym)?
>>> Yes. And the full name is 'over current protection'.
>>
>> Thanks and this leads to second thing - you encode register value
>> instead of logical value. This must be a logical value in mA, so
>> "richtek,bled-ocp-microamp".
> 
> We already have common properties for setting current of LEDs. We should 
> use that here I think.

It might not be exactly the same. We have "led-max-microamp" which is
the maximum allowed current. I guess over-current protection level  is
slightly higher (e.g. led-max-microamp + 1). IOW, led-max-microamp is
something which still can be set and used by system/hardware. OCP should
not.


Best regards,
Krzysztof

Re: [PATCH 1/2] dt-bindings: backlight: rt4831: Add the new property for ocp level selection

[ChiYuan Huang]

Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> 於 2022年6月2日 週四 下午9:58寫道：
>
> On 02/06/2022 15:56, Rob Herring wrote:
> > On Thu, May 26, 2022 at 12:32:12PM +0200, Krzysztof Kozlowski wrote:
> >> On 26/05/2022 10:13, ChiYuan Huang wrote:
> >>> Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> 於 2022年5月26日 週四 下午4:06寫道：
> >>>>
> >>>> On 26/05/2022 05:16, cy_huang wrote:
> >>>>> From: ChiYuan Huang <cy_huang@richtek.com>
> >>>>>
> >>>>> Add the new property for ocp level selection.
> >>>>>
> >>>>> Signed-off-by: ChiYuan Huang <cy_huang@richtek.com>
> >>>>> ---
> >>>>>  .../bindings/leds/backlight/richtek,rt4831-backlight.yaml         | 8 ++++++++
> >>>>>  include/dt-bindings/leds/rt4831-backlight.h                       | 5 +++++
> >>>>>  2 files changed, 13 insertions(+)
> >>>>>
> >>>>> diff --git a/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml b/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml
> >>>>> index e0ac686..c1c59de 100644
> >>>>> --- a/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml
> >>>>> +++ b/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml
> >>>>> @@ -47,6 +47,14 @@ properties:
> >>>>>      minimum: 0
> >>>>>      maximum: 3
> >>>>>
> >>>>> +  richtek,bled-ocp-sel:
> >>>>
> >>>> Skip "sel" as it is a shortcut of selection. Name instead:
> >>>> "richtek,backlight-ocp"
> >>>>
> >>> OK, if so, do I need to rename all properties from 'bled' to 'backlight' ?
> >>> If  only this property is naming as 'backlight'. it may conflict with
> >>> the others like as "richtek,bled-ovp-sel".
> >>
> >> Ah, no, no need.
> >>
> >>>>
> >>>>> +    description: |
> >>>>> +      Backlight OCP level selection, currently support 0.9A/1.2A/1.5A/1.8A
> >>>>
> >>>> Could you explain here what is OCP (unfold the acronym)?
> >>> Yes. And the full name is 'over current protection'.
> >>
> >> Thanks and this leads to second thing - you encode register value
> >> instead of logical value. This must be a logical value in mA, so
> >> "richtek,bled-ocp-microamp".
> >
> > We already have common properties for setting current of LEDs. We should
> > use that here I think.
>
> It might not be exactly the same. We have "led-max-microamp" which is
> the maximum allowed current. I guess over-current protection level  is
> slightly higher (e.g. led-max-microamp + 1). IOW, led-max-microamp is
> something which still can be set and used by system/hardware. OCP should
> not.
>
Yap, you're right.
From the modern backlight IC design, it uses the boost converter architecture.
This OCP level is to limit the inductor current when the internal MOS
switch turn on.
Details can refer to the below wiki link
https://en.wikipedia.org/wiki/Boost_converter

And based on it, OVP is used to limit the inductor output voltage.
Each channel maximum current is based on the IC affordable limit.
It is more like as what you said 'led-max-microamp'.

So boost voltage level may depend on the LED VF.
The different series of LED may cause different boost voltage.

RT4831's OVP/OCP is not just the protection, more like as the limit.
>
> Best regards,
> Krzysztof

Re: [PATCH 1/2] dt-bindings: backlight: rt4831: Add the new property for ocp level selection

[Krzysztof Kozlowski]

On 02/06/2022 17:31, ChiYuan Huang wrote:
> Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> 於 2022年6月2日 週四 下午9:58寫道：
>>
>> On 02/06/2022 15:56, Rob Herring wrote:
>>> On Thu, May 26, 2022 at 12:32:12PM +0200, Krzysztof Kozlowski wrote:
>>>> On 26/05/2022 10:13, ChiYuan Huang wrote:
>>>>> Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> 於 2022年5月26日 週四 下午4:06寫道：
>>>>>>
>>>>>> On 26/05/2022 05:16, cy_huang wrote:
>>>>>>> From: ChiYuan Huang <cy_huang@richtek.com>
>>>>>>>
>>>>>>> Add the new property for ocp level selection.
>>>>>>>
>>>>>>> Signed-off-by: ChiYuan Huang <cy_huang@richtek.com>
>>>>>>> ---
>>>>>>>  .../bindings/leds/backlight/richtek,rt4831-backlight.yaml         | 8 ++++++++
>>>>>>>  include/dt-bindings/leds/rt4831-backlight.h                       | 5 +++++
>>>>>>>  2 files changed, 13 insertions(+)
>>>>>>>
>>>>>>> diff --git a/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml b/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml
>>>>>>> index e0ac686..c1c59de 100644
>>>>>>> --- a/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml
>>>>>>> +++ b/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml
>>>>>>> @@ -47,6 +47,14 @@ properties:
>>>>>>>      minimum: 0
>>>>>>>      maximum: 3
>>>>>>>
>>>>>>> +  richtek,bled-ocp-sel:
>>>>>>
>>>>>> Skip "sel" as it is a shortcut of selection. Name instead:
>>>>>> "richtek,backlight-ocp"
>>>>>>
>>>>> OK, if so, do I need to rename all properties from 'bled' to 'backlight' ?
>>>>> If  only this property is naming as 'backlight'. it may conflict with
>>>>> the others like as "richtek,bled-ovp-sel".
>>>>
>>>> Ah, no, no need.
>>>>
>>>>>>
>>>>>>> +    description: |
>>>>>>> +      Backlight OCP level selection, currently support 0.9A/1.2A/1.5A/1.8A
>>>>>>
>>>>>> Could you explain here what is OCP (unfold the acronym)?
>>>>> Yes. And the full name is 'over current protection'.
>>>>
>>>> Thanks and this leads to second thing - you encode register value
>>>> instead of logical value. This must be a logical value in mA, so
>>>> "richtek,bled-ocp-microamp".
>>>
>>> We already have common properties for setting current of LEDs. We should
>>> use that here I think.
>>
>> It might not be exactly the same. We have "led-max-microamp" which is
>> the maximum allowed current. I guess over-current protection level  is
>> slightly higher (e.g. led-max-microamp + 1). IOW, led-max-microamp is
>> something which still can be set and used by system/hardware. OCP should
>> not.
>>
> Yap, you're right.

So I am right or Rob?

> From the modern backlight IC design, it uses the boost converter architecture.
> This OCP level is to limit the inductor current when the internal MOS
> switch turn on.
> Details can refer to the below wiki link
> https://en.wikipedia.org/wiki/Boost_converter
> 
> And based on it, OVP is used to limit the inductor output voltage.
> Each channel maximum current is based on the IC affordable limit.
> It is more like as what you said 'led-max-microamp'.
> 
> So boost voltage level may depend on the LED VF.
> The different series of LED may cause different boost voltage.
> 
> RT4831's OVP/OCP is not just the protection, more like as the limit.

This suggests Rob is right, so let's use led-max-microamp property?

Best regards,
Krzysztof

Re: [PATCH 1/2] dt-bindings: backlight: rt4831: Add the new property for ocp level selection

[ChiYuan Huang]

Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> 於 2022年6月6日 週一 上午12:11寫道：
>
> On 02/06/2022 17:31, ChiYuan Huang wrote:
> > Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> 於 2022年6月2日 週四 下午9:58寫道：
> >>
> >> On 02/06/2022 15:56, Rob Herring wrote:
> >>> On Thu, May 26, 2022 at 12:32:12PM +0200, Krzysztof Kozlowski wrote:
> >>>> On 26/05/2022 10:13, ChiYuan Huang wrote:
> >>>>> Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> 於 2022年5月26日 週四 下午4:06寫道：
> >>>>>>
> >>>>>> On 26/05/2022 05:16, cy_huang wrote:
> >>>>>>> From: ChiYuan Huang <cy_huang@richtek.com>
> >>>>>>>
> >>>>>>> Add the new property for ocp level selection.
> >>>>>>>
> >>>>>>> Signed-off-by: ChiYuan Huang <cy_huang@richtek.com>
> >>>>>>> ---
> >>>>>>>  .../bindings/leds/backlight/richtek,rt4831-backlight.yaml         | 8 ++++++++
> >>>>>>>  include/dt-bindings/leds/rt4831-backlight.h                       | 5 +++++
> >>>>>>>  2 files changed, 13 insertions(+)
> >>>>>>>
> >>>>>>> diff --git a/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml b/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml
> >>>>>>> index e0ac686..c1c59de 100644
> >>>>>>> --- a/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml
> >>>>>>> +++ b/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml
> >>>>>>> @@ -47,6 +47,14 @@ properties:
> >>>>>>>      minimum: 0
> >>>>>>>      maximum: 3
> >>>>>>>
> >>>>>>> +  richtek,bled-ocp-sel:
> >>>>>>
> >>>>>> Skip "sel" as it is a shortcut of selection. Name instead:
> >>>>>> "richtek,backlight-ocp"
> >>>>>>
> >>>>> OK, if so, do I need to rename all properties from 'bled' to 'backlight' ?
> >>>>> If  only this property is naming as 'backlight'. it may conflict with
> >>>>> the others like as "richtek,bled-ovp-sel".
> >>>>
> >>>> Ah, no, no need.
> >>>>
> >>>>>>
> >>>>>>> +    description: |
> >>>>>>> +      Backlight OCP level selection, currently support 0.9A/1.2A/1.5A/1.8A
> >>>>>>
> >>>>>> Could you explain here what is OCP (unfold the acronym)?
> >>>>> Yes. And the full name is 'over current protection'.
> >>>>
> >>>> Thanks and this leads to second thing - you encode register value
> >>>> instead of logical value. This must be a logical value in mA, so
> >>>> "richtek,bled-ocp-microamp".
> >>>
> >>> We already have common properties for setting current of LEDs. We should
> >>> use that here I think.
> >>
> >> It might not be exactly the same. We have "led-max-microamp" which is
> >> the maximum allowed current. I guess over-current protection level  is
> >> slightly higher (e.g. led-max-microamp + 1). IOW, led-max-microamp is
> >> something which still can be set and used by system/hardware. OCP should
> >> not.
> >>
> > Yap, you're right.
>
> So I am right or Rob?
>
As I know, both are incorrect.
> > From the modern backlight IC design, it uses the boost converter architecture.
> > This OCP level is to limit the inductor current when the internal MOS
> > switch turn on.
> > Details can refer to the below wiki link
> > https://en.wikipedia.org/wiki/Boost_converter
> >
> > And based on it, OVP is used to limit the inductor output voltage.
> > Each channel maximum current is based on the IC affordable limit.
> > It is more like as what you said 'led-max-microamp'.
> >
> > So boost voltage level may depend on the LED VF.
> > The different series of LED may cause different boost voltage.
> >
> > RT4831's OVP/OCP is not just the protection, more like as the limit.
>
> This suggests Rob is right, so let's use led-max-microamp property?
>
No, the meaning is different. 'led-max-microamp' always means the
channel output current.
It already can be adjusted by backlight brightness node.

For example
low voltage side (3.3~4.4V) to generate the boost voltage to 16~17V,
even 20V for BLED Vout.
This OCP is to limit the input current of low voltage side.

After the explanation, do you still think it's the same thing?
> Best regards,
> Krzysztof

Re: [PATCH 1/2] dt-bindings: backlight: rt4831: Add the new property for ocp level selection

[Krzysztof Kozlowski]

On 06/06/2022 03:39, ChiYuan Huang wrote:
> Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> 於 2022年6月6日 週一 上午12:11寫道：
>>
>> On 02/06/2022 17:31, ChiYuan Huang wrote:
>>> Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> 於 2022年6月2日 週四 下午9:58寫道：
>>>>
>>>> On 02/06/2022 15:56, Rob Herring wrote:
>>>>> On Thu, May 26, 2022 at 12:32:12PM +0200, Krzysztof Kozlowski wrote:
>>>>>> On 26/05/2022 10:13, ChiYuan Huang wrote:
>>>>>>> Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> 於 2022年5月26日 週四 下午4:06寫道：
>>>>>>>>
>>>>>>>> On 26/05/2022 05:16, cy_huang wrote:
>>>>>>>>> From: ChiYuan Huang <cy_huang@richtek.com>
>>>>>>>>>
>>>>>>>>> Add the new property for ocp level selection.
>>>>>>>>>
>>>>>>>>> Signed-off-by: ChiYuan Huang <cy_huang@richtek.com>
>>>>>>>>> ---
>>>>>>>>>  .../bindings/leds/backlight/richtek,rt4831-backlight.yaml         | 8 ++++++++
>>>>>>>>>  include/dt-bindings/leds/rt4831-backlight.h                       | 5 +++++
>>>>>>>>>  2 files changed, 13 insertions(+)
>>>>>>>>>
>>>>>>>>> diff --git a/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml b/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml
>>>>>>>>> index e0ac686..c1c59de 100644
>>>>>>>>> --- a/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml
>>>>>>>>> +++ b/Documentation/devicetree/bindings/leds/backlight/richtek,rt4831-backlight.yaml
>>>>>>>>> @@ -47,6 +47,14 @@ properties:
>>>>>>>>>      minimum: 0
>>>>>>>>>      maximum: 3
>>>>>>>>>
>>>>>>>>> +  richtek,bled-ocp-sel:
>>>>>>>>
>>>>>>>> Skip "sel" as it is a shortcut of selection. Name instead:
>>>>>>>> "richtek,backlight-ocp"
>>>>>>>>
>>>>>>> OK, if so, do I need to rename all properties from 'bled' to 'backlight' ?
>>>>>>> If  only this property is naming as 'backlight'. it may conflict with
>>>>>>> the others like as "richtek,bled-ovp-sel".
>>>>>>
>>>>>> Ah, no, no need.
>>>>>>
>>>>>>>>
>>>>>>>>> +    description: |
>>>>>>>>> +      Backlight OCP level selection, currently support 0.9A/1.2A/1.5A/1.8A
>>>>>>>>
>>>>>>>> Could you explain here what is OCP (unfold the acronym)?
>>>>>>> Yes. And the full name is 'over current protection'.
>>>>>>
>>>>>> Thanks and this leads to second thing - you encode register value
>>>>>> instead of logical value. This must be a logical value in mA, so
>>>>>> "richtek,bled-ocp-microamp".
>>>>>
>>>>> We already have common properties for setting current of LEDs. We should
>>>>> use that here I think.
>>>>
>>>> It might not be exactly the same. We have "led-max-microamp" which is
>>>> the maximum allowed current. I guess over-current protection level  is
>>>> slightly higher (e.g. led-max-microamp + 1). IOW, led-max-microamp is
>>>> something which still can be set and used by system/hardware. OCP should
>>>> not.
>>>>
>>> Yap, you're right.
>>
>> So I am right or Rob?
>>
> As I know, both are incorrect.
>>> From the modern backlight IC design, it uses the boost converter architecture.
>>> This OCP level is to limit the inductor current when the internal MOS
>>> switch turn on.
>>> Details can refer to the below wiki link
>>> https://en.wikipedia.org/wiki/Boost_converter
>>>
>>> And based on it, OVP is used to limit the inductor output voltage.
>>> Each channel maximum current is based on the IC affordable limit.
>>> It is more like as what you said 'led-max-microamp'.
>>>
>>> So boost voltage level may depend on the LED VF.
>>> The different series of LED may cause different boost voltage.
>>>
>>> RT4831's OVP/OCP is not just the protection, more like as the limit.
>>
>> This suggests Rob is right, so let's use led-max-microamp property?
>>
> No, the meaning is different. 'led-max-microamp' always means the
> channel output current.
> It already can be adjusted by backlight brightness node.
> 
> For example
> low voltage side (3.3~4.4V) to generate the boost voltage to 16~17V,
> even 20V for BLED Vout.
> This OCP is to limit the input current of low voltage side.
> 
> After the explanation, do you still think it's the same thing?

This sounds differently so I propose to use this dedicated property with
the changes I asked for.


Best regards,
Krzysztof