Hi

I booted the kernel with below said modification  However the kernel is
crashing. I debugged and found that it is crashing in assembly function
__trap_init(arch/arm/kernel). I think it fails when it tries to load the
exception vectors at the location 0xffff0000.

ENTRY(__trap_init)
                stmfd   sp!, {r4 - r6, lr}

                adr     r1, .LCvectors                  @ set up the vectors
                ldmia   r1, {r1, r2, r3, r4, r5, r6, ip, lr}
                stmia   r0, {r1, r2, r3, r4, r5, r6, ip, lr} <-- Crashes in
this line.

                add     r2, r0, #0x200
                adr     r0, __stubs_start               @ copy stubs to
0x200
                adr     r1, __stubs_end
1:              ldr     r3, [r0], #4
                str     r3, [r2], #4
                cmp     r0, r1
                blt     1b
                LOADREGS(fd, sp!, {r4 - r6, pc})

Any help will be grateful.

Thanking you in advance
Regards
Aman



----- Original Message -----
From: "Martin J. Bligh" <mbligh@aracnet.com>
To: "Aman" <amanullah_khan@hotmail.com>; "MM Linux" <linux-mm@kvack.org>
Sent: Sunday, January 25, 2004 9:19 PM
Subject: Re: Discontiguous memory issue


> > I am working on a customized board which has S3C2410 as its processor.
> > I have applied the following Linux patches patch-2.4.18-rmk6 and
> > patch-2.4.18-RMK6-SWL5.
> > There are  two types of custom hardware with me. One has 64MB contiguous
> > SDRAM and the other has 32 MB with following discontiguous physical
> > memory  map.
> >
> > 1. 0x30000000 to 0x307fffff size is 8MB
> > 2. 0x31000000 to 0x317fffff size is 8MB
> > 3. 0x32000000 to 0x327fffff size is 8MB
> > 4. 0x33000000 to 0x337fffff size is 8MB
> >
> > RAMDISK location 0x31000000 (Maximum size is 7 MB) and ZIMAGE
> > location 0x31700000
> >
> > In the 64 MB hardware, Linux runs without any issues. Because the patch
is
> > for 64MB  contiguous memory. I am able to boot the 32 MB hardware
> > with the same kernel used for 64MB. But in 32MB hardware, it crashes
> > when I  run some of our applications. I assume that this is because the
> > kernel is not configured for the discontiguous memory map.
> >
> > I did the following changes to support discontiguous memory.
> >
> > 1. I changed the MEM_SIZE macro to 32 * 1024 * 1024
> > (include/as/arch/s3c2410.h)
> > 2. Changed the macros in the include/asm/arch/memory.h
> > 3. modified the fixup_s3c2410 () function in
> > arch/arm/mach-s3c2410/arch.c to support 4 memory banks.
> > 4. Enabled CONFIG_DISCONTIGMEM option
> >
> > After doing the above changes, Linux crashes during the bootup.
> > Is my understanding correct ?
> > I have attached the modified files.
> > Any help regarding the discontiguous memory configuration will be
grateful.
> >
> > Thanking you in advance.
>
> Where exactly during bootup are you crashing? If it's before console_init,
> you're going to have some kind of early printk function to do a crude dump
> to the screen or serial port or something. If it's after, then dump all
> the pgdats, and see if it looks good.
>
> Fundamentally, you need to create the pgdats, and fill them out properly,
> describing to the main VM where your memory regions start and end. Most
> of them are in pfn units (page frame number = physaddr / PAGE_SIZE).
> I didn't bother sorting through your files to see if you're doing that ;-)
>
> M.
>
>