linux-kernel - [PATCH v8] Staging: comedi: convert while loop to timeout in ni_mio

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Message-Id: <1389896849-3186-1-git-send-email-chase.southwood@yahoo.com>
Date:	Thu, 16 Jan 2014 12:27:29 -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 v8] 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>
---

Okay, back to v2, basically.  I fixed the checkpatch warning from v2,
and added the error checking that was from v3, but otherwise it is the
same.  Of note, I have used a udelay of 1 here (Greg had suggested to
use 10, but Ian prefers 1 so I have gone with that, and I assume that
cpu_relax is no longer an option.).

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).

8: Revert back to v2, with some small changes (see above).

 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..10c27cb 100644
--- a/drivers/staging/comedi/drivers/ni_mio_common.c
+++ b/drivers/staging/comedi/drivers/ni_mio_common.c
@@ -687,12 +687,22 @@ 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;
+	static const int timeout = 10000;
+	int i;
 
 	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 */
+		for (i = 0; i < timeout; i++) {
+			if (!(ni_readl(AIFIFO_Status_6143) & 0x10))
+				break;
+			udelay(1);
+		}
+		if (i == timeout) {
+			comedi_error(dev, "FIFO flush timeout.");
+		}
 	} else {
 		devpriv->stc_writew(dev, 1, ADC_FIFO_Clear);
 		if (board->reg_type == ni_reg_625x) {
-- 
1.8.4.2

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