linux-kernel - Re: [RESEND PATCH 2/6] soc: Mediatek: Add SCPSYS CPU power domain driver

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Date:	Sat, 25 Jul 2015 17:13:00 +0800
From:	Scott Shu <scott.shu@...iatek.com>
To:	Sascha Hauer <s.hauer@...gutronix.de>
CC:	<yingjoe.chen@...iatek.com>, <robh+dt@...nel.org>,
	<matthias.bgg@...il.com>, <linux@....linux.org.uk>,
	<rchintakuntla@...ium.com>, <lorenzo.pieralisi@....com>,
	<marc.ceeeee@...il.com>, <heiko@...ech.de>,
	<catalin.marinas@....com>, <arnd@...db.de>, <galak@...eaurora.org>,
	<srv_wsdupstream@...iatek.com>,
	<linux-mediatek@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <loda.chou@...iatek.com>,
	<jades.shih@...iatek.com>, <scott.shu@...il.com>
Subject: Re: [RESEND PATCH 2/6] soc: Mediatek: Add SCPSYS CPU power domain
 driver

On Fri, 2015-07-24 at 07:50 +0200, Sascha Hauer wrote:
> On Fri, Jul 24, 2015 at 10:02:03AM +0800, Scott Shu wrote:
> > On Tue, 2015-06-23 at 07:53 +0200, Sascha Hauer wrote:
> > > Hi Scott,
> > > 
> > > On Fri, Jun 19, 2015 at 02:01:17AM +0800, Scott Shu wrote:
> > > > This adds a CPU power domain driver for the Mediatek SCPSYS unit on
> > > > MT6580.
> > > 
> > > This seems to be support for the very same hardware as I am posting
> > > here:
> > > 
> > > https://lkml.org/lkml/2015/6/22/41
> > > 
> > > We should consolidate this.
> > > 
> > > My driver is currently handles all power domains except the CPUs while
> > > yours handles only the CPUs.
> > > I currently haven't looked whether CPUs can just be part of a power
> > > domain aswell, but if that works this would probably be the way to go.
> > > 
> > > Sascha
> > > 
> > > 
> > Hi Sascga,
> > 
> > We had posted new patch set in following link, but still keep our
> > original framework.
> > http://lists.infradead.org/pipermail/linux-mediatek/2015-July/001498.html
> > 
> > As we mentioned in the new email thread, the SMP operations (smp_boot_secondary)
> > will be executed before registering the scpsys_drv driver, so the CPUs power
> > domain is controlled on arch/arm/mach-$(MACHINE) directory. 
> > 
> > Please kindly provide your comments and suggestion. Thank you very much.
> 
> I think that instead of explaining why have to duplicate the code you
> should rather search for ways how the code can be shared. Yes, we'll
> need a second (early) entry point to the driver. Maybe we even have to
> create the shared code which is then called from the driver and your
> early architecture code.
> You'll probably have to do this separation between early code and
> regular driver code in your driver anyway, since I bet the MT6580 also
> has some power domains which shall be controlled by the regular Linux
> power domain code later. Also we probably could control the CPU power
> domains for the MT8173 in the SCPSYS driver aswell, we just don't have
> to because we use PSCI there. You see we are approaching the same
> problem from two different corners. Let's find a way to share the code.
> 
> Sascha
> 
Hi Sascha,
   Thanks. OK, we move all CPU MTCMOS driver from hotplug.c to
mtk-scpsys.c and the test is passed. Next, we need spend some time to
integrate the code better.

Scott

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