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Subject: Re: [PATCH] [MTD] Adjust the NOR CFI flash timeouts to round better
From: Artem Bityutskiy <dedekind1@gmail.com>
To: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Date: Mon, 15 Oct 2012 16:42:36 +0300
In-Reply-To: <20121005183202.GA11385@obsidianresearch.com>
References: <20121005183202.GA11385@obsidianresearch.com>
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Cc: David Woodhouse <dwmw2@infradead.org>, linux-mtd@lists.infradead.org
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On Fri, 2012-10-05 at 12:32 -0600, Jason Gunthorpe wrote:
> -	/* see comments in do_write_oneword() regarding uWriteTimeo. */
> -	unsigned long uWriteTimeout =3D ( HZ / 1000 ) + 1;
> +	/* see comments in do_write_oneword() regarding uWriteTimeo.
> +	   Note: write_buffer commands take longer so we use a higher
> +	   time. The AMD 29LV256M for instance has a datasheet max
> +	   of 1.2ms for page and 600us for byte */
> +	unsigned long uWriteTimeout =3D (HZ / 1500) + 2;

What does HZ / 1500 mean? HZ is amount of timer interrupts per second,
which may be 1/100, or 1/1000, or 1/300, depending on the system.

The CFI code seems to assume that HZ is 1/1000, which is wrong. I think
the entire timeout strategy in this file should be cleaned up. You
should use 'jiffies_to_msecs()' / 'msecs_to_jiffies()' helpers instead
of using 'HZ'. And time-outs should be specified in msecs, not in
jiffies. There should be no things like 'HZ/1500'.

Or do I misunderstand something?

--=20
Best Regards,
Artem Bityutskiy

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