linux-kernel - Re: [PATCH] mtd: fix timeout in M25P80 driver

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Message-Id: <1239953060.3390.239.camel@localhost.localdomain>
Date:	Fri, 17 Apr 2009 10:24:20 +0300
From:	Artem Bityutskiy <dedekind@...radead.org>
To:	Peter Horton <zero@...onel-panic.org>
Cc:	linux-mtd@...ts.infradead.org, dwmw2@...radead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mtd: fix timeout in M25P80 driver

On Mon, 2009-04-13 at 15:26 +0100, Peter Horton wrote:
> Extend erase timeout in M25P80 SPI Flash driver.
> 
> The M25P80 drivers fails erasing sectors on a M25P128 because the ready
> wait timeout is too short. Change the timeout from a simple loop count to a
> suitable number of seconds.
> 
> Signed-off-by: Peter Horton <zero@...onel-panic.org>
> ---
> Index: linux-2.6.29-git12/drivers/mtd/devices/m25p80.c
> ===================================================================
> --- linux-2.6.29-git12.orig/drivers/mtd/devices/m25p80.c	2009-04-12 21:41:16.000000000 +0000
> +++ linux-2.6.29-git12/drivers/mtd/devices/m25p80.c	2009-04-12 21:43:01.000000000 +0000
> @@ -54,7 +54,7 @@
>  #define	SR_SRWD			0x80	/* SR write protect */
>  
>  /* Define max times to check status register before we give up. */
> -#define	MAX_READY_WAIT_COUNT	100000
> +#define	MAX_READY_WAIT_JIFFIES	(10 * HZ)	/* eg. M25P128 specs 6s max sector erase */
>  #define	CMD_SIZE		4
>  
>  #ifdef CONFIG_M25PXX_USE_FAST_READ
> @@ -145,20 +145,20 @@
>   */
>  static int wait_till_ready(struct m25p *flash)
>  {
> -	int count;
> +	unsigned long deadline;
>  	int sr;
>  
> -	/* one chip guarantees max 5 msec wait here after page writes,
> -	 * but potentially three seconds (!) after page erase.
> -	 */
Why did you remove the comment? Is it wrong or useless?

> -	for (count = 0; count < MAX_READY_WAIT_COUNT; count++) {
> +	deadline = jiffies + MAX_READY_WAIT_JIFFIES;
> +
> +	do {
>  		if ((sr = read_sr(flash)) < 0)
>  			break;
>  		else if (!(sr & SR_WIP))
>  			return 0;
>  
> -		/* REVISIT sometimes sleeping would be best */
> -	}
> +		cond_resched();
> +
> +	} while (!time_after_eq(jiffies, deadline));
>  
>  	return 1;
>  }

-- 
Best regards,
Artem Bityutskiy (Битюцкий Артём)

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