linux-kernel - Re: [PATCH 4/5] cpufreq: imx6q: add ldo-bypass support

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Message-ID: <CAOMZO5DzEe91pTv+UkCbj0DzgVDOb9hjuakt9NmpTJnEk-j8UA@mail.gmail.com>
Date:	Wed, 17 Dec 2014 12:36:14 -0200
From:	Fabio Estevam <festevam@...il.com>
To:	Tim Harvey <tharvey@...eworks.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	Shawn Guo <shawn.guo@...escale.com>,
	Lucas Stach <l.stach@...gutronix.de>,
	Silvio F <silvio.fricke@...il.com>,
	Christian Hemp <c.hemp@...tec.de>,
	Russell King <rmk+kernel@....linux.org.uk>,
	Iain Paton <ipaton0@...il.com>
Subject: Re: [PATCH 4/5] cpufreq: imx6q: add ldo-bypass support

Hi Tim,

On Fri, Oct 31, 2014 at 2:27 AM, Tim Harvey <tharvey@...eworks.com> wrote:
> When an external PMIC is used for VDD_SOC and VDD_ARM you can save power by
> bypassing the internal LDO's provided by the anantop regulator as long as
> you are running less than 1.2GHz. If running at 1.2GHz the IMX6 datasheets
> state that you must use the internal LDO's to reduce ripple on the suplies.
>
> A failure to bypass the LDO's when using an external PMIC will result in an
> extra voltage drop (~125mV) between VDD_ARM_IN and VDD_ARM and VDD_SOC_IN and
> VDD_SOC which violates the voltages specificed by the datasheets.
>
> Cc: Philipp Zabel <p.zabel@...gutronix.de>
> Cc: Shawn Guo <shawn.guo@...escale.com>
> Signed-off-by: Tim Harvey <tharvey@...eworks.com>
> ---
>  drivers/cpufreq/imx6q-cpufreq.c | 51 +++++++++++++++++++++++++++++++++++++++++

Shouldn't the LDO bypass support be added into the anatop regulator
driver instead?

What if someone wants to use LDO bypass and not use the cpufreq driver?
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