Re: [PATCH 1/5] soc: mediatek: Add SMI driver

From: Yingjoe Chen <yingjoe.chen@mediatek.com>
To: Paul Bolle <pebolle@tiscali.nl>
Cc: Yong Wu <yong.wu@mediatek.com>,
	Mark Rutland <mark.rutland@arm.com>, <devicetree@vger.kernel.org>,
	<srv_heupstream@mediatek.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Joerg Roedel <joro@8bytes.org>, Will Deacon <will.deacon@arm.com>,
	<linux-kernel@vger.kernel.org>, Tomasz Figa <tfiga@google.com>,
	<iommu@lists.linux-foundation.org>,
	Rob Herring <robh+dt@kernel.org>,
	Daniel Kurtz <djkurtz@google.com>,
	Sasha Hauer <kernel@pengutronix.de>,
	Matthias Brugger <matthias.bgg@gmail.com>,
	<linux-mediatek@lists.infradead.org>,
	Robin Murphy <robin.murphy@arm.com>,
	<linux-arm-kernel@lists.infradead.org>,
	Lucas Stach <l.stach@pengutronix.de>
Subject: Re: [PATCH 1/5] soc: mediatek: Add SMI driver
Date: Tue, 10 Mar 2015 14:17:22 +0800	[thread overview]
Message-ID: <1425968242.4871.136.camel@mtksdaap41> (raw)
In-Reply-To: <1425923977.2317.4.camel@tiscali.nl>

On Mon, 2015-03-09 at 18:59 +0100, Paul Bolle wrote:
> Hi Yong,
> 
> Yong Wu schreef op ma 09-03-2015 om 19:57 [+0800]:
> > On Fri, 2015-03-06 at 12:30 +0100, Paul Bolle wrote:
> > > On Fri, 2015-03-06 at 18:48 +0800, yong.wu@mediatek.com wrote:
> > > > --- a/drivers/soc/mediatek/Kconfig
> > > > +++ b/drivers/soc/mediatek/Kconfig
> > > > @@ -20,3 +20,10 @@ config MT8173_PMIC_WRAP
> > > >  	  PMIC wrapper is a proprietary hardware in MT8173 to make
> > > >  	  communication protocols to access PMIC device.
> > > >  	  This driver implement access protocols for MT8173.
> > > > +
> > > > +config MTK_SMI
> > > > +        bool
> > > 
> > > Nit: make this one tab instead of 8 spaces, please.
> > > 
> > > > +	help
> > > > +	  Smi help enable/disable iommu in mt8173 and control the
> > > > +	  clock of each local arbiter.
> > > > +	  It should be true while MTK_IOMMU enable.
> > > 
> > > I don't think anyone using the *config tools will ever see this text, as
> > > there's no prompt. So you might as well make this a comment or drop it
> > > altogether.
> > > 
> >      We could search it in the tool even though we don't see it. In next
> > version, I will try to make it a comment.
> > > Is this selected by more than just MTK_IOMMU (see 2/5)? If not, I think
> > > MTK_SMI will be set and unset in lockstep with MTK_IOMMU. In other
> > > words, you could as well use one Kconfig symbol.
> > > 
> >     if we disable MTK_IOMMU, the MTK_SMI also should be selected.That is because 
> > if the multimedia h/w want to work, the clock of the local arbiters always should be opened.
> 
> This is a bit confusing, I'm afraid. Do you mean to say that it ought to
> be possible for MTK_SMI to be 'y' even if MTK_IOMMU would be 'n'?

The SMI can be configured to bypass IOMMU and send traffic directly to
memory interface. It is possible to not use IOMMU and have display/MM to
use continuous memory only.

Besides MTK_IOMMU, we expect DRM, VDEC driver to select MTK_SMI as well.

Joe.C