[PATCH] net: macb: Apply RXUBR workaround only to versions with errata

[Harini Katakam]

The interrupt handler contains a workaround for RX hang applicable
to Zynq and AT91 only. Subsequent versions do not need this
workaround. This workaround unecessarily resets RX whenever RX used
bit read is observed, which can be often under heavy traffic. Hence
introduce an CAPS mask and a check to enable this workaround.

Signed-off-by: Harini Katakam <harini.katakam@xxxxxxxxxx>
---
Changes from RFC:
- Use CAPS mask instead introducing and errata field.
- Use check only on RX reset part; ISR should still be cleared.

 drivers/net/ethernet/cadence/macb.h      |  1 +
 drivers/net/ethernet/cadence/macb_main.c | 16 ++++++++++------
 2 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/cadence/macb.h b/drivers/net/ethernet/cadence/macb.h
index 3d45f4c..2b412fa 100644
--- a/drivers/net/ethernet/cadence/macb.h
+++ b/drivers/net/ethernet/cadence/macb.h
@@ -643,6 +643,7 @@
 #define MACB_CAPS_JUMBO				0x00000020
 #define MACB_CAPS_GEM_HAS_PTP			0x00000040
 #define MACB_CAPS_BD_RD_PREFETCH		0x00000080
+#define MACB_CAPS_NEEDS_RSTONUBR		0x00000100
 #define MACB_CAPS_FIFO_MODE			0x10000000
 #define MACB_CAPS_GIGABIT_MODE_AVAILABLE	0x20000000
 #define MACB_CAPS_SG_DISABLED			0x40000000
diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index 66cc792..0bda1cd 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -1416,10 +1416,12 @@ static irqreturn_t macb_interrupt(int irq, void *dev_id)
 		 * section 16.7.4 for details.
 		 */
 		if (status & MACB_BIT(RXUBR)) {
-			ctrl = macb_readl(bp, NCR);
-			macb_writel(bp, NCR, ctrl & ~MACB_BIT(RE));
-			wmb();
-			macb_writel(bp, NCR, ctrl | MACB_BIT(RE));
+			if (bp->caps & MACB_CAPS_NEEDS_RSTONUBR) {
+				ctrl = macb_readl(bp, NCR);
+				macb_writel(bp, NCR, ctrl & ~MACB_BIT(RE));
+				wmb();
+				macb_writel(bp, NCR, ctrl | MACB_BIT(RE));
+			}
 
 			if (bp->caps & MACB_CAPS_ISR_CLEAR_ON_WRITE)
 				queue_writel(queue, ISR, MACB_BIT(RXUBR));
@@ -3864,7 +3866,8 @@ static int at91ether_init(struct platform_device *pdev)
 }
 
 static const struct macb_config at91sam9260_config = {
-	.caps = MACB_CAPS_USRIO_HAS_CLKEN | MACB_CAPS_USRIO_DEFAULT_IS_MII_GMII,
+	.caps = MACB_CAPS_USRIO_HAS_CLKEN |
+		MACB_CAPS_USRIO_DEFAULT_IS_MII_GMII | MACB_CAPS_NEEDS_RSTONUBR,
 	.clk_init = macb_clk_init,
 	.init = macb_init,
 };
@@ -3928,7 +3931,8 @@ static const struct macb_config zynqmp_config = {
 };
 
 static const struct macb_config zynq_config = {
-	.caps = MACB_CAPS_GIGABIT_MODE_AVAILABLE | MACB_CAPS_NO_GIGABIT_HALF,
+	.caps = MACB_CAPS_GIGABIT_MODE_AVAILABLE | MACB_CAPS_NO_GIGABIT_HALF |
+		MACB_CAPS_NEEDS_RSTONUBR,
 	.dma_burst_length = 16,
 	.clk_init = macb_clk_init,
 	.init = macb_init,
-- 
2.7.4