From: Ralf Baechle <ralf@linux-mips.org>
To: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: linux-mips@linux-mips.org
Subject: Re: IP22 64bit kernel
Date: Thu, 13 Sep 2007 00:15:36 +0100 [thread overview]
Message-ID: <20070912231536.GI4571@linux-mips.org> (raw)
In-Reply-To: <20070911213048.GA20579@alpha.franken.de>
On Tue, Sep 11, 2007 at 11:30:48PM +0200, Thomas Bogendoerfer wrote:
> I finally figured out, why 64bit SGI IP22 kernels are broken (at
> least when booted with SGI sash). Looks like sash jumps to an uncached
> XPHYS address instead of the KSEG0 address indicated by the ELF start.
> This messes up bogomips calculation.
>
> I found an interesting piece of code in head.S:
>
> .macro ARC64_TWIDDLE_PC
> #if defined(CONFIG_ARC64) || defined(CONFIG_MAPPED_KERNEL)
> /* We get launched at a XKPHYS address but the kernel is linked
> * to
> run at a KSEG0 address, so jump there. */
> PTR_LA t0, \@f
> jr t0
> \@:
> #endif
> .endm
>
>
> Enabling this for (CONFIG_SGI_IP22 && CONFIG_64BIT) fixes the boot problem.
> It's not big deal to add this, but I'm wondering why we not just always
> use this macro ? What platforms do it break with it ?
I don't think any will break - it's just one of those "optimizations".
Ralf
next prev parent reply other threads:[~2007-09-13 10:42 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-09-11 21:30 IP22 64bit kernel Thomas Bogendoerfer
2007-09-12 23:15 ` Ralf Baechle [this message]
2007-09-13 7:05 ` Kumba
2007-09-13 15:50 ` Ralf Baechle
2007-09-13 18:23 ` Thomas Bogendoerfer
2007-10-17 18:36 ` Ralf Baechle
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