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From: Bjorn Andersson <bjorn@kryo.se>
To: Stephen Boyd <sboyd@codeaurora.org>
Cc: Bjorn Andersson <bjorn.andersson@sonymobile.com>,
	Rob Herring <robh+dt@kernel.org>, Pawel Moll <pawel.moll@arm.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Ian Campbell <ijc+devicetree@hellion.org.uk>,
	Kumar Gala <galak@codeaurora.org>, Bryan Wu <cooloney@gmail.com>,
	Richard Purdie <rpurdie@rpsys.net>,
	Grant Likely <grant.likely@linaro.org>,
	Courtney Cavin <courtney.cavin@sonymobile.com>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Linux LED Subsystem <linux-leds@vger.kernel.org>,
	linux-arm-msm <linux-arm-msm@vger.kernel.org>
Subject: Re: [PATCH v2 2/2] leds: add Qualcomm PM8941 WLED driver
Date: Wed, 18 Feb 2015 06:54:30 -0800	[thread overview]
Message-ID: <CAJAp7OjNK5WhZ62x5+z5RZG_GJ8sDoyyHDRq+BBUUkxY_ndjhw@mail.gmail.com> (raw)
In-Reply-To: <54E3FCD3.4000304@codeaurora.org>

On Tue, Feb 17, 2015 at 6:45 PM, Stephen Boyd <sboyd@codeaurora.org> wrote:
> On 02/17/15 15:02, Bjorn Andersson wrote:
>> On Thu, Feb 12, 2015 at 8:26 PM, Stephen Boyd <sboyd@codeaurora.org> wrote:
[..]
>>> This doesn't seem to do anything for the OVP spike mentioned in this
>>> patch[1]. Do you see that problem on your device? I imagine the PMIC is
>>> the same.
>>>
>>> [1]
>>> https://www.codeaurora.org/cgit/quic/la/kernel/msm/commit/?id=fef9e15072562f0f28dc7066dcdd69388df81ed3
>>>
>> That's odd, I can't find that fix in any officially supported releases
>> for 8974 - which Courtney used as reference for this driver.
>>
>> Just to make sure I understand the solution; when disabling the sinks
>> the over-voltage-protection sometimes triggers, so we should detect
>> that and reset the ovp configuration?
>>
>> I presume the side effect would be that the sinks would not give any
>> output until this is done?
>>
>
> It seems that commit is not very good at describing the problem. From
> what I can tell, the inductor current may spike when the WLED is turned
> off and the switch is stuck on (the circuit is a boost convertor). To
> make sure this doesn't happen, we force an OVP so that the switch is
> known to be open (i.e. off) and thus can't cause the current spike when
> we disable.
>

Apparently that commit is only half of the solution, there's another
commit earlier in history with the same commit message [2].

With both [1] and [2] in place there are a bunch of different
operations going on, so I'm not able to fully map these to your
description - which does make sense.

[2] https://www.codeaurora.org/cgit/quic/la/kernel/msm/commit/?id=b1a2f61113c69d2aba68c583101ac40a05cb2c5b

Regards,
Bjorn

  reply	other threads:[~2015-02-18 14:54 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-01-24  0:54 [PATCH v2 1/2] leds: add DT binding for Qualcomm PM8941 WLED block Bjorn Andersson
2015-01-24  0:54 ` [PATCH v2 2/2] leds: add Qualcomm PM8941 WLED driver Bjorn Andersson
2015-01-24  1:22   ` Bjorn Andersson
2015-01-29 12:48   ` Ivan T. Ivanov
2015-01-29 19:07     ` Bjorn Andersson
2015-02-12 19:20       ` Bryan Wu
2015-02-13  4:07     ` Stephen Boyd
2015-02-13  4:28       ` Ivan T. Ivanov
2015-02-13  4:34         ` Stephen Boyd
2015-02-17 23:05       ` Bjorn Andersson
2015-02-13  4:04   ` Stephen Boyd
2015-02-17 22:14     ` Bryan Wu
2015-02-17 22:30       ` Bjorn Andersson
2015-02-17 22:32         ` Bryan Wu
2015-02-17 23:13     ` Bjorn Andersson
2015-02-13  4:26   ` Stephen Boyd
2015-02-17 23:02     ` Bjorn Andersson
2015-02-18  2:45       ` Stephen Boyd
2015-02-18 14:54         ` Bjorn Andersson [this message]
2015-02-12 19:11 ` [PATCH v2 1/2] leds: add DT binding for Qualcomm PM8941 WLED block Bryan Wu

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