linux-kernel - Re: [RFC v1] regulator: core: introduce regulator chain locking scheme

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Message-ID: <516C2905.8000200@ti.com>
Date:	Mon, 15 Apr 2013 19:21:25 +0300
From:	Andrii Tseglytskyi <andrii.tseglytskyi@...com>
To:	Mark Brown <broonie@...nel.org>
CC:	Grygorii Strashko <grygorii.strashko@...com>,
	Liam Girdwood <liam.r.girdwood@...ux.intel.com>,
	<linux-kernel@...r.kernel.org>,
	Mike Turquette <mturquette@...aro.org>,
	Nishanth Menon <nm@...com>, Tero Kristo <t-kristo@...com>,
	linux-omap <linux-omap@...r.kernel.org>,
	linux-arm <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC v1] regulator: core: introduce regulator chain locking scheme

Hi Mark,

On 04/15/2013 06:50 PM, Mark Brown wrote:
>> In addition, such locking scheme allows to have access to the supplier
>> regulator API from inside child's (consumer) regulator API.
> I've still not seen any use case articulated for doing this...
Use case is introduced in ABB series:

http://www.mail-archive.com/linux-omap@vger.kernel.org/msg88293.html

During voltage scaling we would like to have the following sequence:

cpufreq_cpu0
     |
     |---> set_voltage(ABB)
                 |
                 |->set_voltage(AVS)
                         |
                         |-->set_voltage(smps123)


Where smps123 is a regulator, connected ot i2c bus. In this particular 
case "regulator chain" guarantees proper order of calls of voltage 
scaling sequence.

Regards,
Andrii
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