[PATCH] net/macb: fix ISR clear-on-write behavior only for some SoC

[Nicolas Ferre]

Commit 749a2b6 (net/macb: clear tx/rx completion flags in ISR)
introduces clear-on-write on ISR register. This behavior is not always
implemented when using Cadence MACB/GEM and is breaking other platforms.
We are using a new Device Tree compatibility string and a capability
property to actually activate this clear-on-write behavior on ISR.

Reported-by: Hein Tibosch <hein_tibosch at yahoo.es>
Signed-off-by: Nicolas Ferre <nicolas.ferre at atmel.com>
---
 Documentation/devicetree/bindings/net/macb.txt |  2 ++
 drivers/net/ethernet/cadence/macb.c            | 15 +++++++++++++--
 drivers/net/ethernet/cadence/macb.h            |  5 +++++
 3 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/Documentation/devicetree/bindings/net/macb.txt b/Documentation/devicetree/bindings/net/macb.txt
index 44afa0e..13ec4f6 100644
--- a/Documentation/devicetree/bindings/net/macb.txt
+++ b/Documentation/devicetree/bindings/net/macb.txt
@@ -6,6 +6,8 @@ Required properties:
   Use "cdns,at32ap7000-macb" for other 10/100 usage or use the generic form: "cdns,macb".
   Use "cnds,pc302-gem" for Picochip picoXcell pc302 and later devices based on
   the Cadence GEM, or the generic form: "cdns,gem".
+  Use "cdns,zynq-7000-gem" for devices based on Cadence GEM with alternative
+  options enabled (ISR clear on write).
 - reg: Address and length of the register set for the device
 - interrupts: Should contain macb interrupt
 - phy-mode: String, operation mode of the PHY interface.
diff --git a/drivers/net/ethernet/cadence/macb.c b/drivers/net/ethernet/cadence/macb.c
index 6be513d..628f2b0 100644
--- a/drivers/net/ethernet/cadence/macb.c
+++ b/drivers/net/ethernet/cadence/macb.c
@@ -485,7 +485,8 @@ static void macb_tx_interrupt(struct macb *bp)
 	status = macb_readl(bp, TSR);
 	macb_writel(bp, TSR, status);
 
-	macb_writel(bp, ISR, MACB_BIT(TCOMP));
+	if (bp->caps & MACB_CAPS_ISR_CLEAR_ON_WRITE)
+		macb_writel(bp, ISR, MACB_BIT(TCOMP));
 
 	netdev_vdbg(bp->dev, "macb_tx_interrupt status = 0x%03lx\n",
 		(unsigned long)status);
@@ -738,7 +739,8 @@ static irqreturn_t macb_interrupt(int irq, void *dev_id)
 			 * now.
 			 */
 			macb_writel(bp, IDR, MACB_RX_INT_FLAGS);
-			macb_writel(bp, ISR, MACB_BIT(RCOMP));
+			if (bp->caps & MACB_CAPS_ISR_CLEAR_ON_WRITE)
+				macb_writel(bp, ISR, MACB_BIT(RCOMP));
 
 			if (napi_schedule_prep(&bp->napi)) {
 				netdev_vdbg(bp->dev, "scheduling RX softirq\n");
@@ -1474,6 +1476,10 @@ static const struct of_device_id macb_dt_ids[] = {
 	{ .compatible = "cdns,macb" },
 	{ .compatible = "cdns,pc302-gem" },
 	{ .compatible = "cdns,gem" },
+	{
+		.compatible = "cdns,zynq-7000-gem",
+		.data = (void *)MACB_CAPS_ISR_CLEAR_ON_WRITE,
+	},
 	{ /* sentinel */ }
 };
 MODULE_DEVICE_TABLE(of, macb_dt_ids);
@@ -1484,6 +1490,7 @@ static int __init macb_probe(struct platform_device *pdev)
 	struct macb_platform_data *pdata;
 	struct resource *regs;
 	struct net_device *dev;
+	const struct of_device_id *dev_id;
 	struct macb *bp;
 	struct phy_device *phydev;
 	u32 config;
@@ -1558,6 +1565,10 @@ static int __init macb_probe(struct platform_device *pdev)
 
 	dev->base_addr = regs->start;
 
+	dev_id = of_match_device(macb_dt_ids, &pdev->dev);
+	if (dev_id)
+		bp->caps = (u32)dev_id->data;
+
 	/* Set MII management clock divider */
 	config = macb_mdc_clk_div(bp);
 	config |= macb_dbw(bp);
diff --git a/drivers/net/ethernet/cadence/macb.h b/drivers/net/ethernet/cadence/macb.h
index 993d703..5d622fe 100644
--- a/drivers/net/ethernet/cadence/macb.h
+++ b/drivers/net/ethernet/cadence/macb.h
@@ -323,6 +323,9 @@
 #define MACB_MAN_READ				2
 #define MACB_MAN_CODE				2
 
+/* Capability mask bits */
+#define MACB_CAPS_ISR_CLEAR_ON_WRITE		0x1
+
 /* Bit manipulation macros */
 #define MACB_BIT(name)					\
 	(1 << MACB_##name##_OFFSET)
@@ -574,6 +577,8 @@ struct macb {
 	unsigned int 		speed;
 	unsigned int 		duplex;
 
+	u32			caps;
+
 	phy_interface_t		phy_interface;
 
 	/* AT91RM9200 transmit */
-- 
1.8.0