[PATCH v5 6/9] ARM: shmobile: Add PCIe device tree nodes for R8A7790

[Phil.Edworthy at renesas.com]

Hi Arnd,

On: 25/03/2014 18:42, Arnd wrote:
> Subject: Re: [PATCH v5 6/9] ARM: shmobile: Add PCIe device tree nodes 
for R8A7790
> 
> On Tuesday 25 March 2014 16:56:41 Phil Edworthy wrote:
> > +               /* Map all possible DDR as inbound ranges */
> > +               dma-ranges = <0x42000000 0 0x40000000 0 0x40000000 0 
0x80000000
> > +                             0x43000000 1 0x80000000 1 0x80000000 0 
0x80000000>;
> 
> Typo: 0x43000000 should be 0x42000000 I guess.
I used 0x43000000 as this is a 64-bit type. The OF PCI range code 
currently treats both 32 and 64-bit types the same way, but I thought it 
would be good to set this in case we ever need to use it.
 
> Since you control the mapping, I wonder if you could also do this as
> 
>                dma-ranges = <0x42000000 0 0x00000000 0 0x40000000 0 
0x80000000
>                              0x43000000 0 0x80000000 1 0x80000000 0 
0x80000000>;
> 
> i.e. map all the RAM into PCI bus addresses below the 32-bit boundary.
> This would be really nice from the perspective that now all PCI
> devices could access all of RAM without using an IOMMU or the
> relying on 64-bit master capability.
> 
> The downside of this is that you'd probably need a custom dma_map_ops
> wrapper.
Since the OF PCi range code treats both 32 and 64-bit types the same way, 
my PCIe driver only creates 64-bit mappings. In addition, the PCIe 
controller has to use a 64-bit mapping for anything over 2GiB. Based on 
this, I think it's sensible to leave the mappings as 1-to-1.

Thanks
Phil