Hi Greg,
On 14/08/2017 06:16, Greg Ungerer wrote:
Hi Angelo,
On 12/08/17 21:17, Angelo Dureghello wrote:
On 10/08/2017 09:06, Greg Ungerer wrote:
On 10/08/17 01:32, Angelo Dureghello wrote:
[snip]
sure, on this board http://sysam.it/cff_stmark2.html
there are 128MB of ddr2.
External SDRAM is accessible, at least without any mmc support enabled,
from 0x40000000.
I have following test config:
GNU nano 2.8.6
File: arch/m68k/configs/stmark2_defconfig
CONFIG_LOCALVERSION="stmark2-001"
[snip]
I tried still yesterday a bit, but seems there is no much support for
earlyprintk / low level debug for this architecture.
In case i can try with a gpio toggling routine, at least to find
where kernel stops.
The attached patch, is a quick and dirty early console output method.
It works for me on the m5475, should work for you "as is" on the 5441x too.
It is kind of an early printk. Of course it still needs the early
kernel boot to have succeeded before you will get anything much coming out.
But it is worth trying.
Ok many thanks. Btw i used a __square(); function written in asm, so i am
sure i see the gpio toggling in very early stages.
I am wondering if the non-0 base RAM may be a problem. I have only run
the MMU enabled code on platforms with 0 based RAM so far. But lets see if
the early console trace attached gives us anything before digging into that.
This MCU has sdram area physically mapped at 0x4000 0000 so U-Boot, to be
able to execute the kernel must load it to that location/area anyway.
But i have seen that it is not a problem, after MMU is enabled in head.S
the jump
movel #_vstart,%a0 /* jump to "virtual" space */
jmp %a0@
works fine. Since that range is not hitting anything that is maintained
physical, it can be translated into virtual without any issue.
Yeah, it is not so much the initial start up that I think will
be the problem. More the setup of the MMU mapping tables later
in boot.
After some hard debug, i see the execution stops at:
asmlinkage __visible void __init start_kernel(void)
...
setup_arch(&command_line); setup_mm.c
...
paging_init(); mm/mcfmmu.c
...
empty_zero_page = (void *) alloc_bootmem_pages(PAGE_SIZE);
^line 47 mcfmmu.c
Inside alloc_bootmem_pages(), execution seems to end up finally to
mm/bootmem.c and likely to alloc_bootmem_bdata().
In case i can still proceed to find the exact place where execution stops,
but i suspect in the while(1), line 545.
As a curious thing, i find in a different cf CPU code "m54xx.c"
the following:
void __init config_BSP(char *commandp, int size)
{
#ifdef CONFIG_MMU
cf_bootmem_alloc();
mmu_context_init();
#endif
Do also m5441x.c maybe need this calls ?
Yes, you will need this. So that code above is only getting run when
configured for a 547x CPU family. Attached is a rework of that code
so that it will be run for all ColdFire MMU varients. Can you try
that out?
Would be very nice to have MMU working. Strangely, i don't see any
board_config with it enabled. Was it ever tested on some Coldfire ?
Oh, yeah, I run this on a real M5475 EVB board for every kernel
mainline release, with and without MMU enabled. See the
arch/m68k/configs/m5475evb_defconfig, it will default to having
the MMU enabled.
I have todays linux-4.13-rc5 running on it here now:
# cat /proc/version
Linux version 4.13.0-rc5-00001-gb014090-dirty (gerg@goober) (gcc version 5.4.0
(GCC)) #1 Mon Aug 14 10:14:12 AEST 2017
# cat /proc/cpuinfo
CPU: ColdFire
MMU: ColdFire
FPU: ColdFire
Clocking: 264.1MHz
BogoMips: 264.19
Calibration: 1320960 loops
#
Regards
Greg
Ok, i applied your patch, and still the kernel is hanging silently,
so i started up a new debug session again.
What is actually happening (after your patch has been applied) is:
setup_arch() arch/m68k/kernel/setup_mm.c
paging_init()
memmap_init() mm/page_alloc.c
memmap_init_zone()
__init_single_page()
set_page_links() include/linux/mm.h
set_page_zone()
kernel hangs silently on this line
page->flags &= ~(ZONES_MASK << ZONES_PGSHIFT);
I am wondering how mmu works, so at the moment mmu is enabled,
in head.S, i would expect that code compiled for 0x40001000 would
not run, since jumps would be translated to some different physical
addresses, but execution sill works.
At the same, after enabling mmu i would expect .data vars to be
invalid, since their address would be translated to a different
location, while not, the init values of .data variables are still
valid. In case, i am interested to understand this points.
Regards,
Angelo
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