linux-kernel - Re: [PATCH] spi: limit reaches -1, tested 0

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Date:	Sun, 08 Feb 2009 18:46:47 +0100
From:	Roel Kluin <roel.kluin@...il.com>
To:	Mariusz Ceier <mceier@...il.com>
CC:	David Brownell <david-b@...bell.net>,
	spi-devel-general@...ts.sourceforge.net,
	lkml <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] spi: limit reaches -1, tested 0

Mariusz Ceier wrote:
> Roel Kluin writes in first post:
>> -			while ((read(drv_data) == 0) && limit--);
>> +			while ((read(drv_data) == 0) && --limit);
> 
> Roel Kluin writes in last post:
>> -			while ((read(drv_data) == 0) && limit--);
>> +			while ((read(drv_data) == 0) && limit--)
>> +				cpu_relax();
> 
> so should there be postfix or prefix decrement ? :)

Thanks for spotting, I took the liberty to add David Brownell's Acked-by
in this case.
----------------------->8------------------8<---------------------------
With a postfix decrement limit will reach -1 rather than 0,
so the warning will not be issued.

Signed-off-by: Roel Kluin <roel.kluin@...il.com>
Acked-by: David Brownell <dbrownell@...rs.sourceforge.net>
---
diff --git a/drivers/spi/spi_imx.c b/drivers/spi/spi_imx.c
index 269a55e..b143e8c 100644
--- a/drivers/spi/spi_imx.c
+++ b/drivers/spi/spi_imx.c
@@ -779,7 +779,8 @@ static irqreturn_t interrupt_transfer(struct driver_data *drv_data)
 
 			/* Read trailing bytes */
 			limit = loops_per_jiffy << 1;
-			while ((read(drv_data) == 0) && limit--);
+			while ((read(drv_data) == 0) && --limit)
+				cpu_relax();
 
 			if (limit == 0)
 				dev_err(&drv_data->pdev->dev,
--
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