Re: [PATCH 2/4] soc: mediatek: Init MT8173 scpsys driver earlier

From: James Liao <jamesjj.liao@mediatek.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: <linux-arm-kernel@lists.infradead.org>,
	<devicetree@vger.kernel.org>, <srv_heupstream@mediatek.com>,
	Kevin Hilman <khilman@kernel.org>, <linux-kernel@vger.kernel.org>,
	Daniel Kurtz <djkurtz@chromium.org>,
	<linux-mediatek@lists.infradead.org>,
	Sascha Hauer <kernel@pengutronix.de>,
	Matthias Brugger <matthias.bgg@gmail.com>
Subject: Re: [PATCH 2/4] soc: mediatek: Init MT8173 scpsys driver earlier
Date: Thu, 31 Dec 2015 13:59:26 +0800	[thread overview]
Message-ID: <1451541566.10610.10.camel@mtksdaap41> (raw)
In-Reply-To: <6145950.8rtkDup7QD@wuerfel>

Hi Arnd,

On Wed, 2015-12-30 at 11:35 +0100, Arnd Bergmann wrote:
> On Wednesday 30 December 2015 18:12:08 James Liao wrote:
> > On Wed, 2015-12-30 at 09:52 +0100, Arnd Bergmann wrote:
> > > On Wednesday 30 December 2015 14:41:44 James Liao wrote:
> > > > Some power domain comsumers may init before module_init.
> > > > So the power domain provider (scpsys) need to be initialized
> > > > earlier too.
> > > > 
> > > > Signed-off-by: James Liao <jamesjj.liao@mediatek.com>
> > > > ---
> > > > 
> > > 
> > > Why?
> > 
> > Some drivers use different init level to ensure they can be initialized
> > before other drivers. To support these drivers, moving scpsys driver's
> > initial function to subsys_init is the most easy way.
> 
> This is just the same generic explanation that you already have.
> 
> Please be more specific what the dependency is and why we can't rely
> on deferred probing here.

In our case, there is a SMI driver provide APIs to control multiple
devices that attached to different power domains.Video encoder / decoder
and GPU drivers are SMI users. It's not easy for SMI users to detect SMI
and scpsys driver are initialized or not. A most easy way to resolve the
init sequence issue is moving SMI and scpsys driver in early init stage.

Do you prefer to keep scpsys driver's init in module_init? If yes, I can
remove this patch in next version.

Best regards,

James