[ARM] dma: RiscPC: don't modify DMA SG entries

We should not be modifying the scatterlist passed to us from the
driver code; doing so breaks assumptions made by the DMA API code,
and could cause problems if the driver retries a transfer using an
old scatterlist.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 9 insertions, 5 deletions

diff --git a/arch/arm/mach-rpc/dma.c b/arch/arm/mach-rpc/dma.c
index 1f77cdca26e9..c47d974d52bd 100644
--- a/arch/arm/mach-rpc/dma.c
+++ b/arch/arm/mach-rpc/dma.c
@@ -32,6 +32,8 @@ struct iomd_dma {
         unsigned long           base;           /* Controller base address */
         int                     irq;            /* Controller IRQ */
         struct scatterlist      cur_sg;         /* Current controller buffer */
+        dma_addr_t              dma_addr;
+        unsigned int            dma_len;
 };
 
 #if 0
@@ -57,10 +59,10 @@ static void iomd_get_next_sg(struct scatterlist *sg, struct iomd_dma *idma)
         unsigned long end, offset, flags = 0;
 
         if (idma->dma.sg) {
-                sg->dma_address = idma->dma.sg->dma_address;
+                sg->dma_address = idma->dma_addr;
                 offset = sg->dma_address & ~PAGE_MASK;
 
-                end = offset + idma->dma.sg->length;
+                end = offset + idma->dma_len;
 
                 if (end > PAGE_SIZE)
                         end = PAGE_SIZE;
@@ -70,12 +72,14 @@ static void iomd_get_next_sg(struct scatterlist *sg, struct iomd_dma *idma)
 
                 sg->length = end - TRANSFER_SIZE;
 
-                idma->dma.sg->length -= end - offset;
-                idma->dma.sg->dma_address += end - offset;
+                idma->dma_len -= end - offset;
+                idma->dma_addr += end - offset;
 
-                if (idma->dma.sg->length == 0) {
+                if (idma->dma_len == 0) {
                         if (idma->dma.sgcount > 1) {
                                 idma->dma.sg = sg_next(idma->dma.sg);
+                                idma->dma_addr = idma->dma.sg->dma_address;
+                                idma->dma_len = idma->dma.sg->length;
                                 idma->dma.sgcount--;
                         } else {
                                 idma->dma.sg = NULL;