[PATCH net 1/2] net: cadence: macb: Disable USRIO register on some platforms

[Neil Armstrong <narmstrong@baylibre.com>]

On some platforms, the macb integration does not use the USRIO
register to configure the (R)MII port and clocks.
When the register is not implemented and the MACB error signal
is connected to the bus error, reading or writing to the USRIO
register can trigger some Imprecise External Aborts on ARM platforms.
---
 drivers/net/ethernet/cadence/macb.c | 29 +++++++++++++++++------------
 1 file changed, 17 insertions(+), 12 deletions(-)

diff --git a/drivers/net/ethernet/cadence/macb.c b/drivers/net/ethernet/cadence/macb.c
index 169059c..3897620 100644
--- a/drivers/net/ethernet/cadence/macb.c
+++ b/drivers/net/ethernet/cadence/macb.c
@@ -2122,7 +2122,9 @@ static void macb_get_regs(struct net_device *dev, struct ethtool_regs *regs,
 	regs_buff[10] = macb_tx_dma(&bp->queues[0], tail);
 	regs_buff[11] = macb_tx_dma(&bp->queues[0], head);
 
-	regs_buff[12] = macb_or_gem_readl(bp, USRIO);
+	if (!of_property_read_bool(bp->pdev->dev.of_node, "no-usrio")) {
+		regs_buff[12] = macb_or_gem_readl(bp, USRIO);
+	}
 	if (macb_is_gem(bp)) {
 		regs_buff[13] = gem_readl(bp, DMACFG);
 	}
@@ -2401,19 +2403,22 @@ static int macb_init(struct platform_device *pdev)
 		dev->hw_features &= ~NETIF_F_SG;
 	dev->features = dev->hw_features;
 
-	val = 0;
-	if (bp->phy_interface == PHY_INTERFACE_MODE_RGMII)
-		val = GEM_BIT(RGMII);
-	else if (bp->phy_interface == PHY_INTERFACE_MODE_RMII &&
-		 (bp->caps & MACB_CAPS_USRIO_DEFAULT_IS_MII))
-		val = MACB_BIT(RMII);
-	else if (!(bp->caps & MACB_CAPS_USRIO_DEFAULT_IS_MII))
-		val = MACB_BIT(MII);
+	/* Some platform do not implement the USRIO register */
+	if (!of_property_read_bool(pdev->dev.of_node, "no-usrio")) {
+		val = 0;
+		if (bp->phy_interface == PHY_INTERFACE_MODE_RGMII)
+			val = GEM_BIT(RGMII);
+		else if (bp->phy_interface == PHY_INTERFACE_MODE_RMII &&
+			 (bp->caps & MACB_CAPS_USRIO_DEFAULT_IS_MII))
+			val = MACB_BIT(RMII);
+		else if (!(bp->caps & MACB_CAPS_USRIO_DEFAULT_IS_MII))
+			val = MACB_BIT(MII);
 
-	if (bp->caps & MACB_CAPS_USRIO_HAS_CLKEN)
-		val |= MACB_BIT(CLKEN);
+		if (bp->caps & MACB_CAPS_USRIO_HAS_CLKEN)
+			val |= MACB_BIT(CLKEN);
 
-	macb_or_gem_writel(bp, USRIO, val);
+		macb_or_gem_writel(bp, USRIO, val);
+	}
 
 	/* Set MII management clock divider */
 	val = macb_mdc_clk_div(bp);
-- 
1.9.1