How to specify IOMMU'able devices in DT (was: [RFC 0/5] ARM: dma-mapping: New dma_map_ops to control IOVA more precisely)

[Marek Szyprowski]

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 at HansenPartnership.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

Best regards
-- 
Marek Szyprowski
Samsung Poland R&D Center