linux-kernel - Re: How to specify IOMMU'able devices in DT

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Message-ID: <20120924.145014.1452596970914043018.hdoyu@nvidia.com>
Date:	Mon, 24 Sep 2012 13:50:14 +0200
From:	Hiroshi Doyu <hdoyu@...dia.com>
To:	"m.szyprowski@...sung.com" <m.szyprowski@...sung.com>
CC:	"James.Bottomley@...senPartnership.com" 
	<James.Bottomley@...senPartnership.com>,
	"swarren@...dotorg.org" <swarren@...dotorg.org>,
	"joerg.roedel@....com" <joerg.roedel@....com>,
	"arnd@...db.de" <arnd@...db.de>, Krishna Reddy <vdumpa@...dia.com>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"minchan@...nel.org" <minchan@...nel.org>,
	"chunsang.jeong@...aro.org" <chunsang.jeong@...aro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"subashrp@...il.com" <subashrp@...il.com>,
	"linaro-mm-sig@...ts.linaro.org" <linaro-mm-sig@...ts.linaro.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"kyungmin.park@...sung.com" <kyungmin.park@...sung.com>,
	"pullip.cho@...sung.com" <pullip.cho@...sung.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: How to specify IOMMU'able devices in DT

Hi Marek,

Marek Szyprowski <m.szyprowski@...sung.com> wrote @ Mon, 24 Sep 2012 13:14:51 +0200:

> Hello,
> 
> On Monday, September 24, 2012 11:45 AM Hiroshi Doyu wrote:
> 
> > On Mon, 24 Sep 2012 11:28:01 +0200
> > James Bottomley <James.Bottomley@...senPartnership.com> wrote:
> > 
> > > On Mon, 2012-09-24 at 12:04 +0300, Hiroshi Doyu wrote:
> > > > diff --git a/drivers/base/platform.c b/drivers/base/platform.c
> > > > index a1a7225..9eae3be 100644
> > > > --- a/drivers/base/platform.c
> > > > +++ b/drivers/base/platform.c
> > > > @@ -21,6 +21,8 @@
> > > >  #include <linux/slab.h>
> > > >  #include <linux/pm_runtime.h>
> > > >
> > > > +#include <asm/dma-iommu.h>
> > > > +
> > > >  #include "base.h"
> > > >
> > > >  #define to_platform_driver(drv)        (container_of((drv), struct
> > > > platform_driver, \
> > > > @@ -305,8 +307,19 @@ int platform_device_add(struct platform_device
> > > > *pdev)
> > > >                  dev_name(&pdev->dev), dev_name(pdev->dev.parent));
> > > >
> > > >         ret = device_add(&pdev->dev);
> > > > -       if (ret == 0)
> > > > -               return ret;
> > > > +       if (ret)
> > > > +               goto failed;
> > > > +
> > > > +#ifdef CONFIG_PLATFORM_ENABLE_IOMMU
> > > > +       if (platform_bus_type.map && !pdev->dev.archdata.mapping) {
> > > > +               ret = arm_iommu_attach_device(&pdev->dev,
> > > > +                                             platform_bus_type.map);
> > > > +               if (ret)
> > > > +                       goto failed;
> > >
> > > This is horrible ... you're adding an architecture specific callback
> > > into our generic code; that's really a no-no.  If the concept of
> > > CONFIG_PLATFORM_ENABE_IOMMU is useful to more than just arm, then this
> > > could become a generic callback.
> > 
> > As mentioned in the original, this is a heck to explain what is
> > needed. I am looking for some generic solution for how to specify
> > IOMMU info for each platform devices. I'm guessing that some other SoC
> > may have the similar requirements on the above. As you mentioned, this
> > solution should be a generic, not arch specific.
> 
> Please read more about bus notifiers. IMHO a good example is provided in 
> the following thread:
> http://www.mail-archive.com/linux-samsung-soc@vger.kernel.org/msg12238.html

This bus notifier seems enough flexible to afford the variation of
IOMMU map info, like Tegra ASID, which could be platform-specific, and
the other could be common too. There's already iommu_bus_notifier
too. I'll try to implement something base on this.

Thanks for the good info.
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