On 05/16/2013 01:29:45 AM, Kevin Hao wrote:
All these boards use the same configuration file p1_p2_rdb_pc.h in
u-boot. So they have the same pci bus address set by the u-boot.
But in some of these boards the bus address set in dtb don't match
the one used by u-boot. And this will trigger a kernel bug in 32bit
kernel and cause the pci device malfunction. For example, on a
p2020rdb-pc board the u-boot use the 0xa0000000 as both bus address
and cpu address for one pci controller and then assign bus address
such as 0xa00004000 to some pci device. But in the kernel, the dtb
set the bus address to 0xe0000000 and the cpu address to 0xa0000000.
The kernel assumes mistakenly the assigned bus address 0xa0004000
in pci device is correct and keep it unchanged. This will definitely
cause the pci device malfunction. I have made two patches to fix
this in the pci subsystem.
http://patchwork.ozlabs.org/patch/243702/
http://patchwork.ozlabs.org/patch/243703/
But I still think it makes sense to set these bus address to match
with the u-boot. This issue can't be reproduced on 36bit kernel.
But I also tweak the 36bit dtb for the above reason.
IIRC the reason for using 0xe0000000 on all PCIe roots is to maximize
the memory that is DMA-addressable without involving swiotlb.
Maybe U-Boot should be fixed?
-Scott
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