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Message-Id: <1431554496-11716-1-git-send-email-nathan.sullivan@ni.com>
Date: Wed, 13 May 2015 17:01:36 -0500
From: Nathan Sullivan <nathan.sullivan@...com>
To: nicolas.ferre@...el.com
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
Nathan Sullivan <nathan.sullivan@...com>
Subject: [PATCH] net: macb: Add better comment for RXUBR handling
Describe the handler for RXUBR better with a new comment.
Signed-off-by: Nathan Sullivan <nathan.sullivan@...com>
Reviewied-by: Josh Cartwright <joshc@...com>
Reviewied-by: Ben Shelton <ben.shelton@...com>
---
drivers/net/ethernet/cadence/macb.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/drivers/net/ethernet/cadence/macb.c b/drivers/net/ethernet/cadence/macb.c
index 61aa570..5f10dfc 100644
--- a/drivers/net/ethernet/cadence/macb.c
+++ b/drivers/net/ethernet/cadence/macb.c
@@ -1037,6 +1037,12 @@ static irqreturn_t macb_interrupt(int irq, void *dev_id)
* add that if/when we get our hands on a full-blown MII PHY.
*/
+ /* There is a hardware issue under heavy load where DMA can
+ * stop, this causes endless "used buffer descriptor read"
+ * interrupts but it can be cleared by re-enabling RX. See
+ * the at91 manual, section 41.3.1 or the Zynq manual
+ * section 16.7.4 for details.
+ */
if (status & MACB_BIT(RXUBR)) {
ctrl = macb_readl(bp, NCR);
macb_writel(bp, NCR, ctrl & ~MACB_BIT(RE));
--
1.7.10.4
--
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