linux-kernel - [PATCH 48/49] serial: bfin_sport_uart: speed up sport RX sample rate to be 3% faster

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Date:	Fri, 22 Oct 2010 11:21:27 -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 48/49] serial: bfin_sport_uart: speed up sport RX sample rate to be 3% faster

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

The actual uart baud rate of devices vary between +/-2% of what is
asked.  The SPORT RX sample rate should be faster than double of the
worst case.  Otherwise, wrong data may be received.  So set SPORT RX
clock to be 3% faster in general.

Reported-by: Olivier STOCK <ostockemer@...ca.fr>
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.c |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/drivers/serial/bfin_sport_uart.c b/drivers/serial/bfin_sport_uart.c
index 5318dd3..6f1b51e 100644
--- a/drivers/serial/bfin_sport_uart.c
+++ b/drivers/serial/bfin_sport_uart.c
@@ -131,7 +131,12 @@ static int sport_uart_setup(struct sport_uart_port *up, int size, int baud_rate)
 	pr_debug("%s RCR1:%x, RCR2:%x\n", __func__, SPORT_GET_RCR1(up), SPORT_GET_RCR2(up));
 
 	tclkdiv = sclk / (2 * baud_rate) - 1;
-	rclkdiv = sclk / (2 * baud_rate * 2) - 1;
+	/* The actual uart baud rate of devices vary between +/-2%. The sport
+	 * RX sample rate should be faster than the double of the worst case,
+	 * otherwise, wrong data are received. So, set sport RX clock to be
+	 * 3% faster.
+	 */
+	rclkdiv = sclk / (2 * baud_rate * 2 * 97 / 100) - 1;
 	SPORT_PUT_TCLKDIV(up, tclkdiv);
 	SPORT_PUT_RCLKDIV(up, rclkdiv);
 	SSYNC();
-- 
1.7.2

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