[PATCH 07/11] swiotlb: Add support for systems with highmem

Becky Bruce
2008-12-19T05:13:41Z

On highmem systems, the original dma buffer might not
have a virtual mapping - we need to kmap it in to perform
the bounce. Extract the code that does the actual
copy into a function that does the kmap if highmem
is enabled, and defaults to the normal swiotlb memcpy
if not.

Signed-off-by: Becky Bruce <beckyb@kernel.crashing.org>
---
lib/swiotlb.c | 53 +++++++++++++++++++++++++++++++++++++++++++++--------
1 files changed, 45 insertions(+), 8 deletions(-)

diff --git a/lib/swiotlb.c b/lib/swiotlb.c
index e9d5bf6..ab5d3d7 100644
--- a/lib/swiotlb.c
+++ b/lib/swiotlb.c
@@ -14,6 +14,7 @@
* 04/07/.. ak Better overflow handling. Assorted fixes.
* 05/09/10 linville Add support for syncing ranges, support syncing for
* DMA_BIDIRECTIONAL mappings, miscellaneous cleanup.
+ * 08/12/11 beckyb Add highmem support
*/

#include <linux/cache.h>
@@ -24,6 +25,7 @@
#include <linux/string.h>
#include <linux/types.h>
#include <linux/ctype.h>
+#include <linux/highmem.h>

#include <asm/io.h>
#include <asm/dma.h>
@@ -306,6 +308,45 @@ static int is_swiotlb_buffer(char *addr)
}

/*
+ * Bounce: copy the swiotlb buffer back to the original dma location
+ */
+void swiotlb_bounce(phys_addr_t phys, char *dma_addr, size_t size,
+ enum dma_data_direction dir)
+{
+#ifdef CONFIG_HIGHMEM
+ /* The buffer may not have a mapping. Map it in and copy */
+ unsigned int offset = ((unsigned long)phys &
+ ((1 << PAGE_SHIFT) - 1));
+ char *buffer;
+ unsigned int sz = 0;
+ unsigned long flags;
+
+ while (size) {
+ sz = ((PAGE_SIZE - offset) > size) ? size :
+ PAGE_SIZE - offset;
+ local_irq_save(flags);
+ buffer = kmap_atomic(pfn_to_page(phys >> PAGE_SHIFT),
+ KM_BOUNCE_READ);
+ if (dir == DMA_TO_DEVICE)
+ memcpy(dma_addr, buffer + offset, sz);
+ else
+ memcpy(buffer + offset, dma_addr, sz);
+ kunmap_atomic(buffer, KM_BOUNCE_READ);
+ local_irq_restore(flags);
+ size -= sz;
+ phys += sz;
+ dma_addr += sz;
+ offset = 0;
+ }
+#else
+ if (dir == DMA_TO_DEVICE)
+ memcpy(dma_addr, phys_to_virt(phys), size);
+ else
+ memcpy(phys_to_virt(phys), dma_addr, size);
+#endif
+}
+
+/*
* Allocates bounce buffer and returns its kernel virtual address.
*/
static void *
@@ -402,7 +443,7 @@ found:
for (i = 0; i < nslots; i++)
io_tlb_orig_addr[index+i] = phys + (i << IO_TLB_SHIFT);
if (dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL)
- memcpy(dma_addr, phys_to_virt(phys), size);
+ swiotlb_bounce(phys, dma_addr, size, DMA_TO_DEVICE);

return dma_addr;
}
@@ -422,11 +463,7 @@ unmap_single(struct device *hwdev, char *dma_addr, size_t size, int dir)
* First, sync the memory before unmapping the entry
*/
if (phys && ((dir == DMA_FROM_DEVICE) || (dir == DMA_BIDIRECTIONAL)))
- /*
- * bounce... copy the data back into the original buffer * and
- * delete the bounce buffer.
- */
- memcpy(phys_to_virt(phys), dma_addr, size);
+ swiotlb_bounce(phys, dma_addr, size, DMA_FROM_DEVICE);

/*
* Return the buffer to the free list by setting the corresponding
@@ -466,13 +503,13 @@ sync_single(struct device *hwdev, char *dma_addr, size_t size,
switch (target) {
case SYNC_FOR_CPU:
if (likely(dir == DMA_FROM_DEVICE || dir == DMA_BIDIRECTIONAL))
- memcpy(phys_to_virt(phys), dma_addr, size);
+ swiotlb_bounce(phys, dma_addr, size, DMA_FROM_DEVICE);
else
BUG_ON(dir != DMA_TO_DEVICE);
break;
case SYNC_FOR_DEVICE:
if (likely(dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL))
- memcpy(dma_addr, phys_to_virt(phys), size);
+ swiotlb_bounce(phys, dma_addr, size, DMA_TO_DEVICE);
else
BUG_ON(dir != DMA_FROM_DEVICE);
break;
--
1.5.6.5