linux-kernel - Re: [PATCH] ARM: dts: imx6sx-sdb: Remove cpufreq OPP override

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Date:   Fri, 5 May 2017 13:11:05 +0300
From:   Leonard Crestez <leonard.crestez@....com>
To:     Shawn Guo <shawnguo@...nel.org>, Marek Vasut <marex@...x.de>
CC:     Peter Chen <Peter.Chen@....com>, Anson Huang <Anson.Huang@....com>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Sascha Hauer <kernel@...gutronix.de>,
        Fabio Estevam <fabio.estevam@....com>,
        "Fabio Estevam" <festevam@...il.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] ARM: dts: imx6sx-sdb: Remove cpufreq OPP override

On Fri, 2017-05-05 at 09:18 +0800, Shawn Guo wrote:
> On Thu, May 04, 2017 at 04:34:14PM +0200, Marek Vasut wrote:
> > If you model the
> > power distribution correctly, the OPP hackery can be removed.

> The OPP hackery can be removed even without reg_arm/reg_soc modeling.
> That's why we can do hackery dropping and reg_arm/reg_soc modeling in
> separate patches.
> 
> @Leonard, if someday we support 'LDO bypass' mode in upstream kernel,
> the OPP hackery needs to be back in some way even with reg_arm/reg_soc
> modeling in place, right?  Or will we have a better way to ensure SW1A
> rail can always feed a correct voltage directly to reg_arm®_soc?

Maybe? Or maybe the cpufreq driver could detect this situation and
handle it internally. In the vendor tree this the cpufreq driver has a
special fsl,arm-soc-shared property for this anyway.

I posted another RFC at upstreaming ldo-bypass recently but it did not
handle this particular case of a shared input rail. It can be handled
separately.

See: https://lkml.org/lkml/2017/3/22/640

But getting that series to an acceptable state might take a long time.

-- 
Regards,
Leonard