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Date:	Sun, 25 Jan 2009 04:18:23 -0600
From:	"Kevin D. Kissell" <kevink@paralogos.com>
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To:	"David VomLehn (dvomlehn)" <dvomlehn@cisco.com>
CC:	linux-mips@linux-mips.org,
	"Dezhong Diao (dediao)" <dediao@cisco.com>,
	"Victor Williams Jr (williavi)" <williavi@cisco.com>,
	"Michael Sundius -X (msundius - Yoh Services LLC at Cisco)" 
	<msundius@cisco.com>
Subject: Re: 2.6.28 will not boot on 24K processor, ebase incorrectly modified
 in set_uncached_handler
References: <FF038EB85946AA46B18DFEE6E6F8A28976825D@xmb-rtp-218.amer.cisco.com>
In-Reply-To: <FF038EB85946AA46B18DFEE6E6F8A28976825D@xmb-rtp-218.amer.cisco.com>
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David VomLehn (dvomlehn) wrote:
> The 2.6.28 kernel dies in memcpy when called from set_vi_srs_handler on
> a
> 24K processor. The problem is that ebase has an invalid value. The
> original
> value of ebase comes from a bootmem allocation, but the following code
> in
> set_uncached_handler takes a perfectly good kseg0 address and turns it
> into
> an invalid kseg1 address.
>
> 	if (cpu_has_mips_r2)
> 		ebase += (read_c0_ebase() & 0x3ffff000);
>
> This code was added in commit 566f74f6b2f8b85d5b8d6caaf97e5672cecd3e3e.
>   
I remember worrying about why it was "+=" and not "=" when others had 
problems with that patch. See the thread "NXP STB225 board support" from 
January 8 or so.  When I asked about that, I got a comment that the add 
operation was correct, but that patch *should* have said "uncached_ebase 
+= (read_c0_ebase() & 0x3ffff000);"  I guess uncache_ebase is assumed to 
contain something interesting in some non-address bits. Try pre-pending 
"uncached_" to that "ebase"...

          Regards,

          Kevin K.