net: macb: get DMA bus width from design config register

Get DMA bus width from design config register

Signed-off-by: Bo Shen <voice.shen@atmel.com>
Signed-off-by: Andreas Bießmann <andreas.devel@googlemail.com>

drivers/net/macb.c

@@ -621,6 +621,24 @@ static u32 gem_mdc_clk_div(int id, struct macb_device *macb)
 	return config;
 }
 
+/*
+ * Get the DMA bus width field of the network configuration register that we
+ * should program. We find the width from decoding the design configuration
+ * register to find the maximum supported data bus width.
+ */
+static u32 macb_dbw(struct macb_device *macb)
+{
+	switch (GEM_BFEXT(DBWDEF, gem_readl(macb, DCFG1))) {
+	case 4:
+		return GEM_BF(DBW, GEM_DBW128);
+	case 2:
+		return GEM_BF(DBW, GEM_DBW64);
+	case 1:
+	default:
+		return GEM_BF(DBW, GEM_DBW32);
+	}
+}
+
 int macb_eth_initialize(int id, void *regs, unsigned int phy_addr)
 {
 	struct macb_device *macb;
@@ -665,7 +683,7 @@ int macb_eth_initialize(int id, void *regs, unsigned int phy_addr)
 	 */
 	if (macb_is_gem(macb)) {
 		ncfgr = gem_mdc_clk_div(id, macb);
-		ncfgr |= GEM_BF(DBW, 1);
+		ncfgr |= macb_dbw(macb);
 	} else {
 		ncfgr = macb_mdc_clk_div(id, macb);
 	}

drivers/net/macb.h

@@ -58,6 +58,9 @@
 #define MACB_WOL				0x00c4
 #define MACB_MID				0x00fc
 
+/* GEM specific register offsets */
+#define GEM_DCFG1				0x0280
+
 /* Bitfields in NCR */
 #define MACB_LB_OFFSET				0
 #define MACB_LB_SIZE				1
@@ -242,6 +245,14 @@
 #define MACB_IDNUM_SIZE				16
 
 /* Bitfields in DCFG1 */
+#define GEM_DBWDEF_OFFSET			25
+#define GEM_DBWDEF_SIZE				3
+
+/* constants for data bus width */
+#define GEM_DBW32				0
+#define GEM_DBW64				1
+#define GEM_DBW128				2
+
 /* Constants for CLK */
 #define MACB_CLK_DIV8				0
 #define MACB_CLK_DIV16				1