ARM: riscpc: dma: improve address/length writing

Rearrange writing the DMA addresses to generate more efficient code.

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

diff --git a/arch/arm/mach-rpc/dma.c b/arch/arm/mach-rpc/dma.c
index e2b9c95..6140472 100644 (file)
--- a/arch/arm/mach-rpc/dma.c
+++ b/arch/arm/mach-rpc/dma.c
@@ -100,7 +100,7 @@ static irqreturn_t iomd_dma_handle(int irq, void *dev_id)
        struct iomd_dma *idma = dev_id;
        unsigned long base = idma->base;
        unsigned int state = idma->state;
-       unsigned int status;
+       unsigned int status, cur, end;
 
        do {
                status = iomd_readb(base + ST);
@@ -110,21 +110,17 @@ static irqreturn_t iomd_dma_handle(int irq, void *dev_id)
                if ((state ^ status) & DMA_ST_AB)
                        iomd_get_next_sg(idma);
 
-               switch (status & (DMA_ST_OFL | DMA_ST_AB)) {
-               case DMA_ST_OFL:                        /* OIA */
-               case DMA_ST_AB:                         /* .IB */
-                       iomd_writel(idma->cur_addr, base + CURA);
-                       iomd_writel(idma->cur_len, base + ENDA);
-                       state = DMA_ST_AB;
-                       break;
-
-               case DMA_ST_OFL | DMA_ST_AB:            /* OIB */
-               case 0:                                 /* .IA */
-                       iomd_writel(idma->cur_addr, base + CURB);
-                       iomd_writel(idma->cur_len, base + ENDB);
-                       state = 0;
-                       break;
+               // This efficiently implements state = OFL != AB ? AB : 0
+               state = ((status >> 2) ^ status) & DMA_ST_AB;
+               if (state) {
+                       cur = CURA;
+                       end = ENDA;
+               } else {
+                       cur = CURB;
+                       end = ENDB;
                }
+               iomd_writel(idma->cur_addr, base + cur);
+               iomd_writel(idma->cur_len, base + end);
 
                if (status & DMA_ST_OFL &&
                    idma->cur_len == (DMA_END_S|DMA_END_L))