Commit dc7d5cf2 authored by Chris Metcalf's avatar Chris Metcalf
Browse files

tile PCI RC: add dma_get_required_mask() 



The standard kernel function dma_get_required_mask() uses the
highest DRAM address to determine if 32-bit or 64-bit DMA addressing
is needed.  This only works on architectures that have direct mapping
between the PA and the PCI address space, i.e. those that don't have
I/O TLBs or have I/O TLB but choose to use direct mapping.  Neither
of these are true for tilegx.  Whether to use 64-bit DMA should depend
on the PCI device's capability only, not on the amount of DRAM
installeds, so we now advertise a 64-bit DMA mask unconditionally.

Signed-off-by: default avatarChris Metcalf <cmetcalf@tilera.com>
parent 8d9e53b9

arch/tile/include/asm/dma-mapping.h

+4 −0
Original line number Diff line number Diff line
@@ -20,6 +20,10 @@ 
#include <linux/cache.h>

#include <linux/io.h>



#ifdef __tilegx__

#define ARCH_HAS_DMA_GET_REQUIRED_MASK

#endif



extern struct dma_map_ops *tile_dma_map_ops;

extern struct dma_map_ops *gx_pci_dma_map_ops;

extern struct dma_map_ops *gx_legacy_pci_dma_map_ops;

arch/tile/kernel/pci-dma.c

+18 −0
Original line number Diff line number Diff line
@@ -607,3 +607,21 @@ int dma_set_coherent_mask(struct device *dev, u64 mask) 
}

EXPORT_SYMBOL(dma_set_coherent_mask);

#endif



#ifdef ARCH_HAS_DMA_GET_REQUIRED_MASK

/*

 * The generic dma_get_required_mask() uses the highest physical address

 * (max_pfn) to provide the hint to the PCI drivers regarding 32-bit or

 * 64-bit DMA configuration. Since TILEGx has I/O TLB/MMU, allowing the

 * DMAs to use the full 64-bit PCI address space and not limited by

 * the physical memory space, we always let the PCI devices use

 * 64-bit DMA if they have that capability, by returning the 64-bit

 * DMA mask here. The device driver has the option to use 32-bit DMA if

 * the device is not capable of 64-bit DMA.

 */

u64 dma_get_required_mask(struct device *dev)

{

	return DMA_BIT_MASK(64);

}

EXPORT_SYMBOL_GPL(dma_get_required_mask);

#endif

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