net: macb: Add on the fly CPU endianness detection

Program management descriptor's access mode according to the
dynamically detected CPU endianness.

Signed-off-by: Arun Chandran <achandran@mvista.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Tested-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 18 insertions, 4 deletions

diff --git a/drivers/net/ethernet/cadence/macb.c b/drivers/net/ethernet/cadence/macb.c
index 05fb36da0cff..1fe8b946243a 100644
--- a/drivers/net/ethernet/cadence/macb.c
+++ b/drivers/net/ethernet/cadence/macb.c
@@ -1578,6 +1578,7 @@ static u32 macb_dbw(struct macb *bp)
 static void macb_configure_dma(struct macb *bp)
 {
         u32 dmacfg;
+        u32 tmp, ncr;
 
         if (macb_is_gem(bp)) {
                 dmacfg = gem_readl(bp, DMACFG) & ~GEM_BF(RXBS, -1L);
@@ -1586,10 +1587,23 @@ static void macb_configure_dma(struct macb *bp)
                         dmacfg = GEM_BFINS(FBLDO, bp->dma_burst_length, dmacfg);
                 dmacfg |= GEM_BIT(TXPBMS) | GEM_BF(RXBMS, -1L);
                 dmacfg &= ~GEM_BIT(ENDIA_PKT);
-                /* Tell the chip to byteswap descriptors on big-endian hosts */
-#ifdef __BIG_ENDIAN
-                dmacfg |= GEM_BIT(ENDIA_DESC);
-#endif
+
+                /* Find the CPU endianness by using the loopback bit of net_ctrl
+                 * register. save it first. When the CPU is in big endian we
+                 * need to program swaped mode for management descriptor access.
+                 */
+                ncr = macb_readl(bp, NCR);
+                __raw_writel(MACB_BIT(LLB), bp->regs + MACB_NCR);
+                tmp =  __raw_readl(bp->regs + MACB_NCR);
+
+                if (tmp == MACB_BIT(LLB))
+                        dmacfg &= ~GEM_BIT(ENDIA_DESC);
+                else
+                        dmacfg |= GEM_BIT(ENDIA_DESC); /* CPU in big endian */
+
+                /* Restore net_ctrl */
+                macb_writel(bp, NCR, ncr);
+
                 if (bp->dev->features & NETIF_F_HW_CSUM)
                         dmacfg |= GEM_BIT(TXCOEN);
                 else