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

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Date:   Thu, 2 Jun 2022 15:58:55 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Rob Herring <robh@...nel.org>
Cc:     ChiYuan Huang <u0084500@...il.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Lee Jones <lee.jones@...aro.org>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        jingoohan1@...il.com, Pavel Machek <pavel@....cz>, deller@....de,
        cy_huang <cy_huang@...htek.com>, lucas_tsai@...htek.com,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, dri-devel@...ts.freedesktop.org,
        linux-fbdev@...r.kernel.org,
        Linux LED Subsystem <linux-leds@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] dt-bindings: backlight: rt4831: Add the new property
 for ocp level selection

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@...aro.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@...htek.com>
>>>>>
>>>>> Add the new property for ocp level selection.
>>>>>
>>>>> Signed-off-by: ChiYuan Huang <cy_huang@...htek.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