linux-kernel - [PATCH] serial: ifx6x60: ifx_spi_write don't need to do mrdy

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Date:	Mon, 19 Nov 2012 05:07:10 -0500
From:	Jun Chen <jun.d.chen@...el.com>
To:	Greg KH <gregkh@...uxfoundation.org>
Cc:	Alan Cox <alan@...ux.intel.com>, Bi Chao <chao.bi@...el.com>,
	Jun Chen <jun.d.chen@...el.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	serial <linux-serial@...r.kernel.org>
Subject: [PATCH] serial: ifx6x60: ifx_spi_write don't need to do
 mrdy_assert when fifo is not empty


This patch check whether the fifo lenth is empty before writing new data to fifo.If condition
is true,ifx_spi_write need to trigger one mrdy_assert. If condition is false,the mrdy_assert
will be trigger by the next ifx_spi_io.
Cc: Bi Chao <chao.bi@...el.com>
Signed-off-by: Chen Jun <jun.d.chen@...el.com>
---
 drivers/tty/serial/ifx6x60.c |   14 +++++++++++---
 1 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/serial/ifx6x60.c b/drivers/tty/serial/ifx6x60.c
index 5b9bc19..aa01989 100644
--- a/drivers/tty/serial/ifx6x60.c
+++ b/drivers/tty/serial/ifx6x60.c
@@ -469,9 +469,17 @@ static int ifx_spi_write(struct tty_struct *tty, const unsigned char *buf,
 {
 	struct ifx_spi_device *ifx_dev = tty->driver_data;
 	unsigned char *tmp_buf = (unsigned char *)buf;
-	int tx_count = kfifo_in_locked(&ifx_dev->tx_fifo, tmp_buf, count,
-				   &ifx_dev->fifo_lock);
-	mrdy_assert(ifx_dev);
+	int tx_count;
+	unsigned long flags;
+	bool is_fifo_empty;
+
+	spin_lock_irqsave(&ifx_dev->fifo_lock, flags);
+	is_fifo_empty = kfifo_is_empty(&ifx_dev->tx_fifo);
+	tx_count = kfifo_in(&ifx_dev->tx_fifo, tmp_buf, count);
+	spin_unlock_irqrestore(&ifx_dev->fifo_lock, flags);
+	if (is_fifo_empty)
+		mrdy_assert(ifx_dev);
+
 	return tx_count;
 }
 
-- 
1.7.4.1



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