[U-Boot] [PATCH v2] net/designware: Consecutive writes to the same register to be avoided

[Dinh Nguyen]

This commit is an add-on to f6c4191f. There are a few registers where
consecutive writes to the same location should be avoided or have a delay.

According to Synopsys, here is a list of the registers and bit(s) where
consecutive writes should be avoided or a delay is required:

DMA Registers:
Register 0        Bit 7
Register 6        All bits except for 24, 16-13, 2-1.

GMAC Registers:
Registers 0-3     All bits
Registers 6-7     All bits
Register 10       All bits
Register 11       All bits except for 5-6.
Registers 16-47   All bits
Register 48       All bits except for 18-16, 14.
Register 448      Bit 4.
Register 459      Bits 0-3.

Reviewd-by: Matthew Gerlach <mgerlach at altera.com>
Signed-off-by: Dinh Nguyen <dinguyen at altera.com>
---
 drivers/net/designware.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/designware.c b/drivers/net/designware.c
index e8e669b..980b92f 100644
--- a/drivers/net/designware.c
+++ b/drivers/net/designware.c
@@ -163,8 +163,8 @@ static int dw_eth_init(struct eth_device *dev, bd_t *bis)
 	writel(FIXEDBURST | PRIORXTX_41 | BURST_16,
 			&dma_p->busmode);
 
-	writel(FLUSHTXFIFO | readl(&dma_p->opmode), &dma_p->opmode);
-	writel(STOREFORWARD | TXSECONDFRAME, &dma_p->opmode);
+	writel(readl(&dma_p->opmode) | FLUSHTXFIFO | STOREFORWARD | 
+		TXSECONDFRAME, &dma_p->opmode);
 
 	conf = FRAMEBURSTENABLE | DISABLERXOWN;
 
-- 
1.7.9.5