linux-kernel - [PATCH 01/25] serial: bfin_sport_uart: work around anomaly 05000473 (make 32bit fifo read atomic)

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Message-Id: <1274460714-11277-1-git-send-email-gregkh@suse.de>
Date:	Fri, 21 May 2010 09:51:30 -0700
From:	Greg Kroah-Hartman <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org
Cc:	Sonic Zhang <sonic.zhang@...log.com>,
	Mike Frysinger <vapier@...too.org>,
	Greg Kroah-Hartman <gregkh@...e.de>
Subject: [PATCH 01/25] serial: bfin_sport_uart: work around anomaly 05000473 (make 32bit fifo read atomic)

From: Sonic Zhang <sonic.zhang@...log.com>

We cannot let a 32-bit RX FIFO read be interrupted otherwise a fake RX
underflow error might be generated.

URL: http://blackfin.uclinux.org/gf/tracker/5145

Signed-off-by: Sonic Zhang <sonic.zhang@...log.com>
Signed-off-by: Mike Frysinger <vapier@...too.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
---
 drivers/serial/bfin_sport_uart.h |   16 +++++++++++++++-
 1 files changed, 15 insertions(+), 1 deletions(-)

diff --git a/drivers/serial/bfin_sport_uart.h b/drivers/serial/bfin_sport_uart.h
index abe0361..9791fcc 100644
--- a/drivers/serial/bfin_sport_uart.h
+++ b/drivers/serial/bfin_sport_uart.h
@@ -37,7 +37,21 @@
 #define SPORT_GET_TFSDIV(sport)		bfin_read16(((sport)->port.membase + OFFSET_TFSDIV))
 #define SPORT_GET_TX(sport)		bfin_read16(((sport)->port.membase + OFFSET_TX))
 #define SPORT_GET_RX(sport)		bfin_read16(((sport)->port.membase + OFFSET_RX))
-#define SPORT_GET_RX32(sport)		bfin_read32(((sport)->port.membase + OFFSET_RX))
+/*
+ * If another interrupt fires while doing a 32-bit read from RX FIFO,
+ * a fake RX underflow error will be generated.  So disable interrupts
+ * to prevent interruption while reading the FIFO.
+ */
+#define SPORT_GET_RX32(sport) \
+({ \
+	unsigned int __ret; \
+	if (ANOMALY_05000473) \
+		local_irq_disable(); \
+	__ret = bfin_read32((sport)->port.membase + OFFSET_RX); \
+	if (ANOMALY_05000473) \
+		local_irq_enable(); \
+	__ret; \
+})
 #define SPORT_GET_RCR1(sport)		bfin_read16(((sport)->port.membase + OFFSET_RCR1))
 #define SPORT_GET_RCR2(sport)		bfin_read16(((sport)->port.membase + OFFSET_RCR2))
 #define SPORT_GET_RCLKDIV(sport)	bfin_read16(((sport)->port.membase + OFFSET_RCLKDIV))
-- 
1.7.0.3

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