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[ARM] 3439/2: xsc3: add I/O coherency support

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Patch from Lennert Buytenhek

This patch adds support for the I/O coherent cache available on the
xsc3.  The approach is to provide a simple API to determine whether the
chipset supports coherency by calling arch_is_coherent() and then
setting the appropriate system memory PTE and PMD bits.  In addition,
we call this API on dma_alloc_coherent() and dma_map_single() calls.
A generic version exists that will compile out all the coherency-related
code that is not needed on the majority of ARM systems.

Note that we do not check for coherency in the dma_alloc_writecombine()
function as that still requires a special PTE setting.  We also don't
touch dma_mmap_coherent() as that is a special ARM-only API that is by
definition only used on non-coherent system.

Signed-off-by: Deepak Saxena <dsaxena@plexity.net>
Signed-off-by: Lennert Buytenhek <buytenh@wantstofly.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Lennert Buytenhek
2006-04-02 00:07:39 +01:00
committed by Russell King
parent d3f4c571b6
commit 23759dc643
10 changed files with 80 additions and 8 deletions
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8
include/asm-arm/memory.h
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@ -234,6 +234,14 @@ static inline __deprecated void *bus_to_virt(unsigned long x)
#define virt_to_dma(dev, addr) (__arch_virt_to_dma(dev, addr))
#endif
/*
* Optional coherency support. Currently used only by selected
* Intel XSC3-based systems.
*/
#ifndef arch_is_coherent
#define arch_is_coherent() 0
#endif
#endif
#include <asm-generic/memory_model.h>