Re: IP32 prom crashes due to __pa() funkiness

Hi!

Did you try to use PHYS_OFFSET > 0 ?  __pa() ist still (as of
d3fbd83ff545e49e2a0a5ca0f00dda4eedaf8be7) defined as (casts omitted):

#define __pa(x) (x - (x < CKSEG0 ? PAGE_OFFSET:CKSEG0) + PHYS_OFFSET)

This gives __pa(CKSEG0) == PHYS_OFFSET, which will never work for
PHYS_OFFSET > 0. A quick fix (assuming this was the cause for failure)
could be:

========================================================================

--- d3fbd83ff545e49e2a0a5ca0f00dda4eedaf8be7/include/asm-mips/page.h	Sat Mar 10 08:43:17 2007
+++ quickfix/include/asm-mips/page.h	Sun Mar 18 10:24:34 2007

@@ -150,7 +150,7 @@ typedef struct { unsigned long pgprot; }
  * __pa()/__va() should be used only during mem init.
  */
 #if defined(CONFIG_64BIT) && !defined(CONFIG_BUILD_ELF64)
-#define __pa_page_offset(x)	((unsigned long)(x) < CKSEG0 ? PAGE_OFFSET : CKSEG0)
+#define __pa_page_offset(x)	((unsigned long)(x) < CKSEG0 ? PAGE_OFFSET : CKSEG0+PHYS_OFFSET)
 #else
 #define __pa_page_offset(x)	PAGE_OFFSET
 #endif

Signed-off-by: peter fuerst <redacted>

========================================================================

Of course, "#define PAGE_OFFSET (CAC_BASE + PHYS_OFFSET)" is also needed.

kind regards

peter


On Sat, 17 Mar 2007, Kumba wrote:

Date: Sat, 17 Mar 2007 14:53:23 -0400
From: Kumba <redacted>
To: Franck Bui-Huu <redacted>
Cc: peter fuerst <redacted>
Subject: Re: IP32 prom crashes due to __pa() funkiness

Franck Bui-Huu wrote:

quoted

Hi,

[snip]

quoted

Well, it means that you previously used CONFIG_BUILD_ELF64=y (this
implied that PAGE_OFFSET is in XKPHYS) whereas your kernel has CKSEG
load address (symbols need PAGE_OFFSET in CKSEG for address
translation).

So the question is why can't you use CONFIG_BUILD_ELF64=n (and
reagarding the current definition of CONFIG_BUILD_ELF64).

[snip]

quoted

It makes me think that I posted a patch for that a couple of weeks ago:

http://marc.theaimsgroup.com/?l=linux-mips&m=117154480225936&w=2
http://marc.theaimsgroup.com/?l=linux-mips&m=117154480126802&w=2
http://marc.theaimsgroup.com/?l=linux-mips&m=117154587014827&w=2

Basically this patch removes CONFIG_BUILD_ELF64 and makes Kbuild to use
'-msym32' switch if you really need it. Kbuild makes its choice according
the load address of your kernel image.

Could you give it a try ? This patch was based on 2.6.20 but it should
apply fine on a 2.6.21-rc[12].

Tested, and it still failed.

And I didn't always use CONFIG_BUILD_ELF64.  In fact, for the longest time (up
until 2.6.17) I built IP32 and 64bit IP22 kernels without CONFIG_BUILD_eLF64,
passing -mabi=o64 (a.k.a., the binutils hack).  This let me use the plain
'vmlinux' target w/o the need for an objcopy to boot these systems.  After
2.6.17, the nature of o64 was mostly neutered, so I switched to using
CONFIG_BUILD_ELF64 and the 'vmlinux.32' target, as this is apparently the way
Debian builds their IP32 kernels (and was the way geoman/spbecker said I
should've been using all along).

So with the changes brought in by __pa(), I suppose a new, RightWay(TM) to build
IP32 (and conversely, 64bit IP22) kernels needs to be found.  These two systems
are particularly wacky, hence why they need a bit more special care than more
traditional, proper, 64bit systems like Origin and Octane.

Also, Peter raises a good point in this case.  It sounds like a re-thinking of
how all this address stuff is handled will fix not only special cases like
IP32/IP22, but the really weird systems, like IP28, as well.  Which would be a
big plus in my opinion.


--Kumba

--
Gentoo/MIPS Team Lead

"Such is oft the course of deeds that move the wheels of the world: small hands
do them because they must, while the eyes of the great are elsewhere."  --Elrond