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Re: [Xen-devel] [LINUX] dma: Use swiotlb mask for coherent mappings too

As we're going to have a swiotlb_{alloc,free}_coherent implementation after the 
with lib/swiotlb.c anyway, wouldn't it make sense to have 
call the former rather than setting up things by itself? If course, this will 
pressure on the swiotlb memory, but otoh it could reduce the likelihood of the
contiguous region setup failing (especially if those are of non-zero order).


>>> Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> 20.12.06 06:14 >>>
Hi Keir:

[LINUX] dma: Use swiotlb mask for coherent mappings too

The recent change to use a default DMA bit width of 30 bits (required
by chips like the b44) only converted the streaming DMA primitives.
The coherent mappings are still hard-coded to 31 bits.  This means that
b44 still doesn't work under Xen.

This patch makes the io_tlb_dma_bits variable global and uses it for
coherent memory mappings.

Thanks to Calvin Webster for providing a machine with a b44 and 2G
of memory I've been able to verify that this finally makes the b44
work under Xen.

Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>

Visit Openswan at http://www.openswan.org/ 
Email: Herbert Xu ~{PmV>HI~} <herbert@xxxxxxxxxxxxxxxxxxx>
Home Page: http://gondor.apana.org.au/~herbert/ 
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt 
diff -r 057f7c4dbed1 linux-2.6-xen-sparse/arch/i386/kernel/pci-dma-xen.c
--- a/linux-2.6-xen-sparse/arch/i386/kernel/pci-dma-xen.c       Tue Dec 19 
12:00:11 2006 +0000
+++ b/linux-2.6-xen-sparse/arch/i386/kernel/pci-dma-xen.c       Wed Dec 20 
16:07:24 2006 +1100
@@ -15,6 +15,7 @@
 #include <linux/version.h>
 #include <asm/io.h>
 #include <xen/balloon.h>
+#include <asm/swiotlb.h>
 #include <asm/tlbflush.h>
 #include <asm-i386/mach-xen/asm/swiotlb.h>
 #include <asm/bug.h>
@@ -183,8 +184,8 @@ void *dma_alloc_coherent(struct device *
        ret = (void *)vstart;
        if (ret != NULL) {
-               /* NB. Hardcode 31 address bits for now: aacraid limitation. */
-               if (xen_create_contiguous_region(vstart, order, 31) != 0) {
+               if (xen_create_contiguous_region(vstart, order,
+                                                io_tlb_dma_bits) != 0) {
                        free_pages(vstart, order);
                        return NULL;
diff -r 057f7c4dbed1 linux-2.6-xen-sparse/arch/i386/kernel/swiotlb.c
--- a/linux-2.6-xen-sparse/arch/i386/kernel/swiotlb.c   Tue Dec 19 12:00:11 
2006 +0000
+++ b/linux-2.6-xen-sparse/arch/i386/kernel/swiotlb.c   Wed Dec 20 16:07:24 
2006 +1100
@@ -98,7 +98,7 @@ static struct phys_addr {
 static DEFINE_SPINLOCK(io_tlb_lock);
-static unsigned int io_tlb_dma_bits = DEFAULT_IO_TLB_DMA_BITS;
+unsigned int io_tlb_dma_bits = DEFAULT_IO_TLB_DMA_BITS;
 static int __init
 setup_io_tlb_bits(char *str)
diff -r 057f7c4dbed1 
--- a/linux-2.6-xen-sparse/include/asm-i386/mach-xen/asm/swiotlb.h      Tue Dec 
19 12:00:11 2006 +0000
+++ b/linux-2.6-xen-sparse/include/asm-i386/mach-xen/asm/swiotlb.h      Wed Dec 
20 16:07:24 2006 +1100
@@ -34,6 +34,8 @@ extern int swiotlb_dma_supported(struct 
 extern int swiotlb_dma_supported(struct device *hwdev, u64 mask);
 extern void swiotlb_init(void);
+extern int io_tlb_dma_bits;
 extern int swiotlb;

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