problems to boot 2.6.23 kernel on XILINX ppc with 8Mbytes of RAM

problems to boot 2.6.23 kernel on XILINX ppc with 8Mbytes of RAM

[manu]

Hello,
I work on a custom board based on a virtex 2 pro FPGA and 8Mbytes of SDRAM.
Untill now I used a 2.4.31 linux ppc kernel with John Williams patches
and uclinux distribution and everything worked perfectly.
I've decided to move to the latest 2.6 version from kernel.org
(2.6.23.1) with an initramfs containing a busybox.
My complete zImage including the initramfs has a size of 900Kbytes.
I made some tests with a ML300 board and I managed to get a shell easily.
When I migrated to the custom board, I had the "Now booting the kernel"
message and then nothing.
When I trace the code running on the ppc with the debugger, execution
seems to be stuck in some early initialization code.
I managed to reproduce the problem on the ML300 using "mem=8m" parameter
on the bootline.
With "mem=16m" the kernel boots correctly.
I'm really surprised by the amount of RAM required to boot the kernel.
Is there a way to make it boot with only 8Mbytes of RAM ?
Thanks for your help.

Manu

Re: problems to boot 2.6.23 kernel on XILINX ppc with 8Mbytes of RAM

[Magnus Hjorth]

[-- Attachment #1: Type: text/plain, Size: 1504 bytes --]

Hello Manu,

Could you try the attached patch to arch/ppc/mm/4xx_mmu.c and see if it 
solves your problem?

Best regards,
Magnus


manu wrote:
> Hello,
> I work on a custom board based on a virtex 2 pro FPGA and 8Mbytes of SDRAM.
> Untill now I used a 2.4.31 linux ppc kernel with John Williams patches
> and uclinux distribution and everything worked perfectly.
> I've decided to move to the latest 2.6 version from kernel.org
> (2.6.23.1) with an initramfs containing a busybox.
> My complete zImage including the initramfs has a size of 900Kbytes.
> I made some tests with a ML300 board and I managed to get a shell easily.
> When I migrated to the custom board, I had the "Now booting the kernel"
> message and then nothing.
> When I trace the code running on the ppc with the debugger, execution
> seems to be stuck in some early initialization code.
> I managed to reproduce the problem on the ML300 using "mem=8m" parameter
> on the bootline.
> With "mem=16m" the kernel boots correctly.
> I'm really surprised by the amount of RAM required to boot the kernel.
> Is there a way to make it boot with only 8Mbytes of RAM ?
> Thanks for your help.
>
> Manu
> _______________________________________________
> Linuxppc-embedded mailing list
> Linuxppc-embedded@ozlabs.org
> https://ozlabs.org/mailman/listinfo/linuxppc-embedded
>   


-- 

Magnus Hjorth, M.Sc.
Omnisys Instruments AB
Gruvgatan 8
SE-421 30  Västra Frölunda, SWEDEN
Phone: +46 31 734 34 09
Fax: +46 31 734 34 29
http://www.omnisys.se 


[-- Attachment #2: 4xx_mmu.patch --]
[-- Type: text/plain, Size: 589 bytes --]

--- 4xx_mmu_old.c	2007-10-25 08:54:46.000000000 +0200
+++ 4xx_mmu.c	2007-10-25 08:55:57.000000000 +0200
@@ -105,7 +105,7 @@
 		return s;
 	}
 
-	while (s <= (total_lowmem - LARGE_PAGE_SIZE_16M)) {
+	while (s + LARGE_PAGE_SIZE_16M <= total_lowmem) {
 		pmd_t *pmdp;
 		unsigned long val = p | _PMD_SIZE_16M | _PAGE_HWEXEC | _PAGE_HWWRITE;
 
@@ -120,7 +120,7 @@
 		s += LARGE_PAGE_SIZE_16M;
 	}
 
-	while (s <= (total_lowmem - LARGE_PAGE_SIZE_4M)) {
+	while (s + LARGE_PAGE_SIZE_4M <= total_lowmem) {
 		pmd_t *pmdp;
 		unsigned long val = p | _PMD_SIZE_4M | _PAGE_HWEXEC | _PAGE_HWWRITE;
 

Re: problems to boot 2.6.23 kernel on XILINX ppc with 8Mbytes of RAM

[manu]

Hello Magnus,
your patch solved the problem.
Thank you.

Manu

Magnus Hjorth a écrit :
> Hello Manu,
>
> Could you try the attached patch to arch/ppc/mm/4xx_mmu.c and see if
> it solves your problem?
>
> Best regards,
> Magnus
>
>
> manu wrote:
>> Hello,
>> I work on a custom board based on a virtex 2 pro FPGA and 8Mbytes of
>> SDRAM.
>> Untill now I used a 2.4.31 linux ppc kernel with John Williams patches
>> and uclinux distribution and everything worked perfectly.
>> I've decided to move to the latest 2.6 version from kernel.org
>> (2.6.23.1) with an initramfs containing a busybox.
>> My complete zImage including the initramfs has a size of 900Kbytes.
>> I made some tests with a ML300 board and I managed to get a shell
>> easily.
>> When I migrated to the custom board, I had the "Now booting the kernel"
>> message and then nothing.
>> When I trace the code running on the ppc with the debugger, execution
>> seems to be stuck in some early initialization code.
>> I managed to reproduce the problem on the ML300 using "mem=8m" parameter
>> on the bootline.
>> With "mem=16m" the kernel boots correctly.
>> I'm really surprised by the amount of RAM required to boot the kernel.
>> Is there a way to make it boot with only 8Mbytes of RAM ?
>> Thanks for your help.
>>
>> Manu
>> _______________________________________________
>> Linuxppc-embedded mailing list
>> Linuxppc-embedded@ozlabs.org
>> https://ozlabs.org/mailman/listinfo/linuxppc-embedded
>>   
>
>
> ------------------------------------------------------------------------
>
> --- 4xx_mmu_old.c	2007-10-25 08:54:46.000000000 +0200
> +++ 4xx_mmu.c	2007-10-25 08:55:57.000000000 +0200
> @@ -105,7 +105,7 @@
>  		return s;
>  	}
>  
> -	while (s <= (total_lowmem - LARGE_PAGE_SIZE_16M)) {
> +	while (s + LARGE_PAGE_SIZE_16M <= total_lowmem) {
>  		pmd_t *pmdp;
>  		unsigned long val = p | _PMD_SIZE_16M | _PAGE_HWEXEC | _PAGE_HWWRITE;
>  
> @@ -120,7 +120,7 @@
>  		s += LARGE_PAGE_SIZE_16M;
>  	}
>  
> -	while (s <= (total_lowmem - LARGE_PAGE_SIZE_4M)) {
> +	while (s + LARGE_PAGE_SIZE_4M <= total_lowmem) {
>  		pmd_t *pmdp;
>  		unsigned long val = p | _PMD_SIZE_4M | _PAGE_HWEXEC | _PAGE_HWWRITE;
>  
>   

Re: problems to boot 2.6.23 kernel on XILINX ppc with 8Mbytes of RAM

[Grant Likely]

On 10/25/07, Magnus Hjorth <mh@omnisys.se> wrote:
> Hello Manu,
>
> Could you try the attached patch to arch/ppc/mm/4xx_mmu.c and see if it
> solves your problem?

Good catch, thanks!

Send you're signed off by line, and I'll for Josh to pick it up.

Reviewed-by: Grant Likely <grant.likely@secretlab.ca>

Cheers,
g.

-- 
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.
grant.likely@secretlab.ca
(403) 399-0195

[PATCH] ppc4xx: mmu_mapin_ram bugfix for booting with mem<16 MB

[Magnus Hjorth]

From: Magnus Hjorth <mh@omnisys.se>

This patch (for 2.6.23.1) fixes an unsigned arithmetic bug causing the
kernel to hang when booting with less than 16 MB of memory on ppc4xx.

Signed-off-by: Magnus Hjorth <mh@omnisys.se>

---

OK, trying to do this by the book now...

--- linux-2.6.23.1/arch/ppc/mm/4xx_mmu.c.orig	2007-10-27 10:14:42.000000000 +0200
+++ linux-2.6.23.1/arch/ppc/mm/4xx_mmu.c	2007-10-27 10:15:34.000000000 +0200
@@ -105,7 +105,7 @@ unsigned long __init mmu_mapin_ram(void)
 		return s;
 	}
 
-	while (s <= (total_lowmem - LARGE_PAGE_SIZE_16M)) {
+	while (s + LARGE_PAGE_SIZE_16M <= total_lowmem) {
 		pmd_t *pmdp;
 		unsigned long val = p | _PMD_SIZE_16M | _PAGE_HWEXEC | _PAGE_HWWRITE;
 
@@ -120,7 +120,7 @@ unsigned long __init mmu_mapin_ram(void)
 		s += LARGE_PAGE_SIZE_16M;
 	}
 
-	while (s <= (total_lowmem - LARGE_PAGE_SIZE_4M)) {
+	while (s + LARGE_PAGE_SIZE_4M <= total_lowmem) {
 		pmd_t *pmdp;
 		unsigned long val = p | _PMD_SIZE_4M | _PAGE_HWEXEC | _PAGE_HWWRITE;