From mboxrd@z Thu Jan  1 00:00:00 1970
From: Scott Wood <scottwood@freescale.com>
Date: Tue, 20 May 2008 10:24:04 -0500
Subject: [U-Boot-Users] [PATCH] Make sleep shell command is reliablefor
 all architectures
In-Reply-To: <1211295950.3617.17.camel@mcmullan-linux.cifs.lab.netapp.com>
References: <20080520142358.5B6CD247A5@gemini.denx.de>
	<1211295950.3617.17.camel@mcmullan-linux.cifs.lab.netapp.com>
Message-ID: <4832ED14.702@freescale.com>
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McMullan, Jason wrote:
> On Tue, 2008-05-20 at 16:23 +0200, Wolfgang Denk wrote:
>> Well, even if this happens, it should not cause get_timer()  to  show
>> such problems. get_timer() returns an "unsigned long" and is counting
>> in milliseconds, so a wrap-around should take about 50 days.
> 
> Yes, but get_timer() is not guaranteed to return 0 to MAX_ULONG, as
> far as I can tell.
> 
> On MIPS (even after my CFG_HZ patch), get_timer() will only return
> 0 to 14316 on a 300MHZ machine, as the 32-bit MIPS tick timer that
> forms the MIPS time base wraps to 0 after 14.316 seconds.
> 
>> I tend to reject this patch because I think we should fix  the  cause
>> of  the  problems  rather than the symptoms - there are more areas in
>> the code that rely on sane behaviour of the get_timer() functione.
> 
> Well, then we've got a big problem on MIPS.

This can be fixed by maintaining the upper bits of the timebase in 
software, as long we can guarantee that get_timer() is called at least 
once per wraparound.  That is, remember the last value, and if the new 
value is less than the old value, increment the upper word.

-Scott