linux-kernel - Re: [RFC PATCH] i2c: busses: i2c-omap: Increase timeout for i2c interrupt

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Date:	Fri, 10 Jul 2015 11:09:35 +0300
From:	Roger Quadros <rogerq@...com>
To:	Vignesh R <vigneshr@...com>, Tony Lindgren <tony@...mide.com>,
	Wolfram Sang <wsa@...-dreams.de>
CC:	<linux-omap@...r.kernel.org>, <linux-i2c@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH] i2c: busses: i2c-omap: Increase timeout for i2c interrupt

Vignesh,

On 10/07/15 08:09, Vignesh R wrote:
> When system is under load and there is an i2c transaction running
> following warning appears on the console:
> 
> [  730.003617] omap_i2c 48070000.i2c: controller timed out
> [  731.023643] omap_i2c 48070000.i2c: controller timed out
> 
> This is because, the completion() call, which is done in bottom half of
> the interrupt handler, happens after the timeout period(1s) has elapsed
> for the wait_for_completion_timeout() in omap_i2c_xfer_msg(). The
> interrupt is raised within a second but due to system load (or other
> interrupts), the bottom half does not get scheduled within a second.
> Hence even though the interrupt has happened within required time frame,
> due to delayed scheduling of bottom half, spurious timeout errors are
> reported on the console and i2c controller is reset.
> 
> i2c timeout is a rare condition, hence increase timeout to 60s in order
> to avoid reporting false timeout events under load.

why not 5s instead of 60s?

cheers,
-roger

> 
> Signed-off-by: Vignesh R <vigneshr@...com>
> ---
> 
> I reproduced this while running i2cdump in a loop and reading from flash
> using dd command.
> 
>  drivers/i2c/busses/i2c-omap.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
> index d1c22e3fdd14..fa7758f0302c 100644
> --- a/drivers/i2c/busses/i2c-omap.c
> +++ b/drivers/i2c/busses/i2c-omap.c
> @@ -50,7 +50,7 @@
>  #define OMAP_I2C_REV_ON_4430_PLUS	0x50400002
>  
>  /* timeout waiting for the controller to respond */
> -#define OMAP_I2C_TIMEOUT (msecs_to_jiffies(1000))
> +#define OMAP_I2C_TIMEOUT (msecs_to_jiffies(60 * 1000))
>  
>  /* timeout for pm runtime autosuspend */
>  #define OMAP_I2C_PM_TIMEOUT		1000	/* ms */
> 
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