[PATCH] powerpc/fsl-pci: Allow 64-bit PCIe devices to DMA to any memory address

[Kumar Gala]

On Dec 1, 2011, at 12:03 AM, Kumar Gala wrote:

> There is an issue on FSL-BookE 64-bit devices (P5020) in which PCIe
> devices that are capable of doing 64-bit DMAs (like an Intel e1000) do
> not function and crash the kernel if we have >4G of memory in the system.
> 
> The reason is that the existing code only sets up one inbound window for
> access to system memory across PCIe.  That window is limited to a 32-bit
> address space.  So on systems we'll end up utilizing SWIOTLB for dma
> mappings.  However SWIOTLB dma ops implement dma_alloc_coherent() as
> dma_direct_alloc_coherent().  Thus we can end up with dma addresses that
> are not accessible because of the inbound window limitation.
> 
> We could possibly set the SWIOTLB alloc_coherent op to
> swiotlb_alloc_coherent() however that does not address the issue since
> the swiotlb_alloc_coherent() will behave almost identical to
> dma_direct_alloc_coherent() since the devices coherent_dma_mask will be
> greater than any address allocated by swiotlb_alloc_coherent() and thus
> we'll never bounce buffer it into a range that would be dma-able.
> 
> The easiest and best solution is to just make it so that a 64-bit
> capable device is able to DMA to any internal system address.
> 
> We accomplish this by opening up a second inbound window that maps all
> of memory above the internal SoC address width so we can set it up to
> access all of the internal SoC address space if needed.
> 
> We than fixup the dma_ops and dma_offset for PCIe devices with a dma
> mask greater than the maximum internal SoC address.
> 
> Signed-off-by: Kumar Gala <galak at kernel.crashing.org>
> ---
> arch/powerpc/sysdev/fsl_pci.c |   55 +++++++++++++++++++++++++++++++++++++++++
> 1 files changed, 55 insertions(+), 0 deletions(-)

applied to merge

- k