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Re: Kernel crash in 2.6.32.6 / bcm1480 with 16k page size

To: linux-mips@linux-mips.org
Subject: Re: Kernel crash in 2.6.32.6 / bcm1480 with 16k page size
From: Guenter Roeck <public@roeck-us.net>
Date: Mon, 1 Feb 2010 07:04:17 -0800 (PST)
In-reply-to: <20100201021854.GA8572@linux-mips.org>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <20100128155514.GA31611@ericsson.com> <20100129132406.GD5685@linux-mips.org> <20100129151220.GA3882@ericsson.com> <4B6316D2.1060006@caviumnetworks.com> <20100129180619.GA20113@linux-mips.org> <20100129183926.GB9895@ericsson.com> <4B632F60.4000604@caviumnetworks.com> <20100129192532.GA11123@ericsson.com> <4B6336F1.8070208@caviumnetworks.com> <20100129195801.GC11123@ericsson.com> <alpine.LFD.2.00.1001310907320.31764@eddie.linux-mips.org> <20100131165503.GA18523@ericsson.com> <20100201021854.GA8572@linux-mips.org>
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Ralf Baechle DL5RB wrote:
> 
> On Sun, Jan 31, 2010 at 08:55:03AM -0800, Guenter Roeck wrote:
> 
>> >  The size of the address space can be probed via CP0 registers (for
>> MIPS 
>> > architecture processors that is).  No need to add any CPU dependencies 
>> > (except from legacy 64-bit MIPS processors perhaps).
>> > 
>> That would help. Do you happen to know which CP0 register(s) to look for
>> ? 
>> I browsed through the MIPS 5K and 20Kc manuals, but didn't find it.
> 
> Write a value with all bits set to c0_entryhi, then read it back again.
> The set bits in the VPN2 bitfield will indicate the size of the virtual
> address range supported.  The MIPS64 documentation also calls this value
> SEGBITS.  The nice thing about this probe is that it is supported for
> all 64-bit MIPS processors except the R8000 which has an entirely
> different
> TLB scheme anyway.
> 
> Similarly it is possible to probe the physical address range in either
> c0_entrylo0 or c0_entrylo1.  This is also of interest on 32-bit
> processors.
> 
>   Ralf
> 
> 
> 

Ok, I'll try that and submit a new set of patches if it works.

Guenter

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