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Date:   Thu, 17 May 2018 20:40:12 +0530
From:   kgunda@codeaurora.org
To:     Rob Herring <robh+dt@kernel.org>
Cc:     Bjorn Andersson <bjorn.andersson@linaro.org>,
        Lee Jones <lee.jones@linaro.org>,
        Daniel Thompson <daniel.thompson@linaro.org>,
        Jingoo Han <jingoohan1@gmail.com>,
        Jacek Anaszewski <jacek.anaszewski@gmail.com>,
        Pavel Machek <pavel@ucw.cz>,
        Mark Rutland <mark.rutland@arm.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
        Linux LED Subsystem <linux-leds@vger.kernel.org>,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        dri-devel <dri-devel@lists.freedesktop.org>,
        linux-fbdev@vger.kernel.org,
        linux-arm-msm <linux-arm-msm@vger.kernel.org>,
        linux-arm-msm-owner@vger.kernel.org
Subject: Re: [PATCH V1 2/5] backlight: qcom-wled: Add support for WLED4
 peripheral
In-Reply-To: <CAL_JsqLQvSpB3CiS1sA5AXwbvC0xkd1HqEYsjY+=oripMXSwuA@mail.gmail.com>
References: <1525341432-15818-1-git-send-email-kgunda@codeaurora.org>
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 <20180507162004.GB2259@tuxbook-pro>
 <f970143860bd64624e7fad58333df1be@codeaurora.org>
 <82fa847760309cb3382bf0a8da50162c@codeaurora.org>
 <CAL_JsqLQvSpB3CiS1sA5AXwbvC0xkd1HqEYsjY+=oripMXSwuA@mail.gmail.com>
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On 2018-05-17 18:01, Rob Herring wrote:
> On Thu, May 17, 2018 at 4:47 AM,  <kgunda@codeaurora.org> wrote:
>> On 2018-05-08 15:55, kgunda@codeaurora.org wrote:
>>> 
>>> On 2018-05-07 21:50, Bjorn Andersson wrote:
>>>> 
>>>> On Thu 03 May 02:57 PDT 2018, Kiran Gunda wrote:
>>>> 
>>>>> WLED4 peripheral is present on some PMICs like pmi8998
>>>>> and pm660l. It has a different register map and also
>>>>> configurations are different. Add support for it.
>>>>> 
>>>> 
>>>> Several things are going on in this patch, it needs to be split to
>>>> not hide the functional changes from the structural/renames.
>>>> 
>>> Ok. I will split it in the next series.
>>>>> 
>>>>> Signed-off-by: Kiran Gunda <kgunda@codeaurora.org>
>>>>> ---
>>>>>  .../bindings/leds/backlight/qcom-wled.txt          | 172 ++++-
>>>>>  drivers/video/backlight/qcom-wled.c                | 749
>>>>> +++++++++++++++------
>>>>>  2 files changed, 696 insertions(+), 225 deletions(-)
>>>>> 
>>>>> diff --git
>>>>> a/Documentation/devicetree/bindings/leds/backlight/qcom-wled.txt
>>>>> b/Documentation/devicetree/bindings/leds/backlight/qcom-wled.txt
>>>>> index fb39e32..0ceffa1 100644
>>>>> --- 
>>>>> a/Documentation/devicetree/bindings/leds/backlight/qcom-wled.txt
>>>>> +++ 
>>>>> b/Documentation/devicetree/bindings/leds/backlight/qcom-wled.txt
>>>>> @@ -1,30 +1,129 @@
>>>>>  Binding for Qualcomm Technologies, Inc. WLED driver
>>>>> 
>>>>> -Required properties:
>>>>> -- compatible: should be "qcom,pm8941-wled"
>>>>> -- reg: slave address
>>>>> -
>>>>> -Optional properties:
>>>>> -- default-brightness: brightness value on boot, value from: 0-4095
>>>>> -       default: 2048
>>>>> -- label: The name of the backlight device
>>>>> -- qcom,cs-out: bool; enable current sink output
>>>>> -- qcom,cabc: bool; enable content adaptive backlight control
>>>>> -- qcom,ext-gen: bool; use externally generated modulator signal to 
>>>>> dim
>>>>> -- qcom,current-limit: mA; per-string current limit; value from 0 
>>>>> to 25
>>>>> -       default: 20mA
>>>>> -- qcom,current-boost-limit: mA; boost current limit; one of:
>>>>> -       105, 385, 525, 805, 980, 1260, 1400, 1680
>>>>> -       default: 805mA
>>>>> -- qcom,switching-freq: kHz; switching frequency; one of:
>>>>> -       600, 640, 685, 738, 800, 872, 960, 1066, 1200, 1371,
>>>>> -       1600, 1920, 2400, 3200, 4800, 9600,
>>>>> -       default: 1600kHz
>>>>> -- qcom,ovp: V; Over-voltage protection limit; one of:
>>>>> -       27, 29, 32, 35
>>>>> -       default: 29V
>>>>> -- qcom,num-strings: #; number of led strings attached; value from 
>>>>> 1 to
>>>>> 3
>>>>> -       default: 2
>>>>> +WLED (White Light Emitting Diode) driver is used for controlling
>>>>> display
>>>>> +backlight that is part of PMIC on Qualcomm Technologies, Inc. 
>>>>> reference
>>>>> +platforms. The PMIC is connected to the host processor via SPMI 
>>>>> bus.
>>>>> +
>>>>> +- compatible
>>>>> +       Usage:        required
>>>>> +       Value type:   <string>
>>>>> +       Definition:   should be "qcom,pm8941-wled" or
>>>>> "qcom,pmi8998-wled".
>>>>> +                     or "qcom,pm660l-wled".
>>>> 
>>>> 
>>>> Better written as
>>>> 
>>>>                 should be one of:
>>>>                         X
>>>>                         Y
>>>>                         Z
>>>> 
>>> Will do it in the next series.
>>>>> 
>>>>> +
>>>>> +- reg
>>>>> +       Usage:        required
>>>>> +       Value type:   <prop encoded array>
>>>>> +       Definition:   Base address of the WLED modules.
>>>>> +
>>>>> +- interrupts
>>>>> +       Usage:        optional
>>>>> +       Value type:   <prop encoded array>
>>>>> +       Definition:   Interrupts associated with WLED. Interrupts 
>>>>> can be
>>>>> +                     specified as per the encoding listed under
>>>>> +                     Documentation/devicetree/bindings/spmi/
>>>>> +                     qcom,spmi-pmic-arb.txt.
>>>> 
>>>> 
>>>> Better to describe that this should be the "short" and "ovp" 
>>>> interrupts
>>>> in this property than in the interrupt-names.
>>>> 
>>> Ok. I will do it in the next series.
>>>>> 
>>>>> +
>>>>> +- interrupt-names
>>>>> +       Usage:        optional
>>>>> +       Value type:   <string>
>>>>> +       Definition:   Interrupt names associated with the 
>>>>> interrupts.
>>>>> +                     Must be "short" and "ovp". The short circuit
>>>>> detection
>>>>> +                     is not supported for PM8941.
>>>>> +
>>>>> +- label
>>>>> +       Usage:        required
>>>>> +       Value type:   <string>
>>>>> +       Definition:   The name of the backlight device
>>>>> +
>>>>> +- default-brightness
>>>>> +       Usage:        optional
>>>>> +       Value type:   <u32>
>>>>> +       Definition:   brightness value on boot, value from: 0-4095
>>>>> +                     Default: 2048
>>>>> +
>>>>> +- qcom,current-limit
>>>>> +       Usage:        optional
>>>>> +       Value type:   <u32>
>>>>> +       Definition:   uA; per-string current limit
>>>> 
>>>> 
>>>> You can't change unit on an existing property, that breaks any 
>>>> existing
>>>> dts using the qcom,pm8941-wled compatible.
>>>> 
>>> 
>>>>> +                     value:
>>>>> +                     For pm8941: from 0 to 25000 with 5000 ua step
>>>>> +                                 Default 20000 uA
>>>>> +                     For pmi8998: from 0 to 30000 with 5000 ua 
>>>>> step
>>>>> +                                  Default 25000 uA.
>>>> 
>>>> 
>>>> These values could be described just as well in mA, so keep the 
>>>> original
>>>> unit - in particular since the boot-limit is in mA...
>>>> 
>>> Ok. Will keep the original as is in the next series.
>> 
>> Here, I may have to go with the approach as in "qcom,ovp". Because for
>> pm8941
>> the current step is 1 mA (I have wrongly mentioned as 5000uA here) and 
>> for
>> PMI8998
>> the current step is 2.5 mA. Hence, I will add another variable
>> "qcom,current-limit-ua"
>> just like "qcom,ovp-mv".
> 
> Use unit suffixes defined in bindings/property-units.txt.
> 
> Rob
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Thanks for pointing it ! hope I can use "qcom,current-limit-microamp" 
and
"qcom,ovp-millivolt". I am asking this because i found only 
"-microvolt".
"-millivolt" is not present in the bindings you pointed.