linux-kernel - [PATCH v7] Staging: comedi: convert while loop to timeout in ni_mio

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Message-Id: <1389813752-3009-1-git-send-email-chase.southwood@yahoo.com>
Date:	Wed, 15 Jan 2014 13:22:32 -0600
From:	Chase Southwood <chase.southwood@...oo.com>
To:	gregkh@...uxfoundation.org
Cc:	abbotti@....co.uk, hsweeten@...ionengravers.com,
	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
	Chase Southwood <chase.southwood@...oo.com>
Subject: [PATCH v7] Staging: comedi: convert while loop to timeout in ni_mio_common.c

This patch for ni_mio_common.c changes out a while loop for a timeout,
which is preferred.

Signed-off-by: Chase Southwood <chase.southwood@...oo.com>
---

Hartley,
I sincerely apologize for the obvious mistake, I thought I had built it
but clearly I made a mistake somewhere, as your observation is exactly
correct.  It is now fixed.

Thanks,
Chase Southwood

2: Changed from simple clean-up to swapping a timeout in for a while loop.

3: Removed extra counter variable, and added error checking.

4: No longer using counter variable, using jiffies instead.

5: udelay for 10u, instead of 1u.

6: Scrap udelay entirely, in favor of cpu_relax. Include asm/processor.h
in order to use cpu_relax.

7: Fix typo (msec vs msecs).

 drivers/staging/comedi/drivers/ni_mio_common.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/comedi/drivers/ni_mio_common.c b/drivers/staging/comedi/drivers/ni_mio_common.c
index 457b884..ab7a74c 100644
--- a/drivers/staging/comedi/drivers/ni_mio_common.c
+++ b/drivers/staging/comedi/drivers/ni_mio_common.c
@@ -55,6 +55,7 @@
 #include <linux/interrupt.h>
 #include <linux/sched.h>
 #include <linux/delay.h>
+#include <asm/processor.h>
 #include "8255.h"
 #include "mite.h"
 #include "comedi_fc.h"
@@ -687,12 +688,21 @@ static void ni_clear_ai_fifo(struct comedi_device *dev)
 {
 	const struct ni_board_struct *board = comedi_board(dev);
 	struct ni_private *devpriv = dev->private;
+	unsigned long timeout;
 
 	if (board->reg_type == ni_reg_6143) {
 		/*  Flush the 6143 data FIFO */
 		ni_writel(0x10, AIFIFO_Control_6143);	/*  Flush fifo */
 		ni_writel(0x00, AIFIFO_Control_6143);	/*  Flush fifo */
-		while (ni_readl(AIFIFO_Status_6143) & 0x10) ;	/*  Wait for complete */
+		/*  Wait for complete */
+		timeout = jiffies + msecs_to_jiffies(500);
+		while (ni_readl(AIFIFO_Status_6143) & 0x10) {
+			if (time_after(jiffies, timeout)) {
+				comedi_error(dev, "FIFO flush timeout.");
+				break;
+			}
+			cpu_relax();
+		}
 	} else {
 		devpriv->stc_writew(dev, 1, ADC_FIFO_Clear);
 		if (board->reg_type == ni_reg_625x) {
-- 
1.8.4.2

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