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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? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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