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? > 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
