Re: [PATCH] leds: leds-pca963x: workaround group blink scaling issue

From	Matt Ranostay <mranostay@gmail.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH] leds: leds-pca963x: workaround group blink scaling issue
Date	2016-10-15 14:10 +0200
Message-ID	<ssvWN-7rU-17@gated-at.bofh.it> (permalink)
References	(1 earlier) <srO5r-3Z3-15@gated-at.bofh.it> <srP1v-4Cs-7@gated-at.bofh.it> <srPbb-4G0-23@gated-at.bofh.it> <ss4jT-6bx-7@gated-at.bofh.it> <ssbEK-2pQ-17@gated-at.bofh.it>
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On Fri, Oct 14, 2016 at 7:20 AM, Tony Lindgren <tony@atomide.com> wrote:
> * Jacek Anaszewski <j.anaszewski@samsung.com> [161013 23:37]:
>> On 10/13/2016 04:20 PM, Matt Ranostay wrote:
>> > On Thu, Oct 13, 2016 at 4:05 PM, Jacek Anaszewski
>> > <j.anaszewski@samsung.com> wrote:
>> > > Why DT property? Is it somehow dependent on the board configuration?
>> > > How this period-scale value is calculated? Is it inferred empirically?
>> > >
>> >
>> > We empirically discovered and verified this with an logic analyzer on
>> > multiple batches of this part.
>> > Reason for the DT entry is we aren't 100% sure that it is always going
>> > to be the same with different board revs.
>> >
>> > Could be that parts clock acts differently with supply voltage.   This
>> > has been calculated by setting it an expected value, and measuring the
>> > actual result with the logic analyzer.
>>
>> I'd like to have DT maintainer's ack for this.
>>
>> Cc Rob and Mark.
>
> How about do this based on the compatible property instead? If there
> are multiple manufacturers for this part and only a certain
> parts have this issue we should have multiple compatible properties.
>

I could only find that NXP as the manufacturer of that part. It is
possible since the clock is internal to the chipset that the vdd of
2.5V is doing something undefined.

> Then if it turns out all of them need this scaling there's no need
> to update the binding.

Understandable.

>
> Regards,
>
> Tony

Thread

[PATCH] leds: leds-pca963x: workaround group blink scaling issue Matt Ranostay <mranostay@gmail.com> - 2016-10-13 15:20 +0200
  Re: [PATCH] leds: leds-pca963x: workaround group blink scaling issue Jacek Anaszewski <j.anaszewski@samsung.com> - 2016-10-13 16:20 +0200
    Re: [PATCH] leds: leds-pca963x: workaround group blink scaling issue Matt Ranostay <mranostay@gmail.com> - 2016-10-13 16:30 +0200
      Re: [PATCH] leds: leds-pca963x: workaround group blink scaling issue Jacek Anaszewski <j.anaszewski@samsung.com> - 2016-10-14 08:40 +0200
        Re: [PATCH] leds: leds-pca963x: workaround group blink scaling issue Tony Lindgren <tony@atomide.com> - 2016-10-14 16:30 +0200
          Re: [PATCH] leds: leds-pca963x: workaround group blink scaling issue Matt Ranostay <mranostay@gmail.com> - 2016-10-15 14:10 +0200
            Re: [PATCH] leds: leds-pca963x: workaround group blink scaling issue Jacek Anaszewski <j.anaszewski@samsung.com> - 2016-10-17 10:00 +0200
              Re: [PATCH] leds: leds-pca963x: workaround group blink scaling issue Rob Herring <robh@kernel.org> - 2016-10-18 15:50 +0200
                Re: [PATCH] leds: leds-pca963x: workaround group blink scaling issue Jacek Anaszewski <j.anaszewski@samsung.com> - 2016-10-18 16:20 +0200
  Re: [PATCH] leds: leds-pca963x: workaround group blink scaling issue Jacek Anaszewski <j.anaszewski@samsung.com> - 2016-10-25 09:20 +0200

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