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

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Message-Id: <1239960088.3390.297.camel@localhost.localdomain>
Date:	Fri, 17 Apr 2009 12:21:28 +0300
From:	Artem Bityutskiy <dedekind@...radead.org>
To:	Peter Horton <phorton@...box.co.uk>
Cc:	Peter Horton <zero@...onel-panic.org>, dwmw2@...radead.org,
	linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mtd: fix timeout in M25P80 driver

On Fri, 2009-04-17 at 09:22 +0100, Peter Horton wrote:
> Artem Bityutskiy wrote:
> > 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?
> > 
> 
> I moved the comment up to the definition of MAX_READY_WAIT_JIFFIES. 
> Looking through the code I missed the fact the driver can generate "chip 
> erase", on the M25P128 the maximum ready timeout for this is 250s !!!

So I assume you are going to send another patch? Also, how about
Andrew's suggestion not to hog CPU?

-- 
Best regards,
Artem Bityutskiy (Битюцкий Артём)

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