Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx> 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@xxxxxxxxxx> 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@xxxxxxxxxx> 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@xxxxxxxxxxx> > >>>>>>> > >>>>>>> Add the new property for ocp level selection. > >>>>>>> > >>>>>>> Signed-off-by: ChiYuan Huang <cy_huang@xxxxxxxxxxx> > >>>>>>> --- > >>>>>>> .../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
