Hi Angelo,
On 20/08/17 23:26, Angelo Dureghello wrote:
> On 20/08/2017 14:44, Greg Ungerer wrote:
>> On 18/08/17 01:02, Angelo Dureghello wrote:
>>> On 14/08/2017 06:16, Greg Ungerer wrote:
>>>> 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);
>>>
>>>>
>>>
Can you run your current code with the console debug code I sent
a little while back?
I ask because I suspect it should give something based on your debug
above. I played around a little trying to fake out my configuration
to make it look like the RAM was non-zero based. I couldn't get a fail,
but I would like to add some more debug to see what is going on with
the page pointers from your debug.
Can you apply the attached patch and get any extra debug?
>>> 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.
>>
>> On the ColdFire the kernel relies on all RAM and IO peripheral
>> addresses) to "hit" the ACR registers - and essentially be passed
>> through as an identity physical = virtual mapping. If you look at
>> the operation of the memory address translation when virtual mode
>> is enabled (in the ColdFire MMU sections of the 5475 and 54411
>> reference manual) you will see that addresses are checked in order
>> to be for the MMUBAR, RAMBAR, ACR, then MMU.
>>
>> For example a kernel address when in supervisor mode will hit
>> ACR1 or ACR3 the way we set them up in arch/m68k/coldfire/head.S.
>> And that is why you see kernel code and data still being valid after
>> the MMU is enabled in virtual mode. No TLB entries required for this.
>>
>> Looking at your call sequence above I can see that the physical
>> RAM start address being non-zero is going to come into play. I'll
>> dig into this a little more tomorrow see if I can figure out what
>> is going on.
>>
>
> Thanks for the kind clarifications.
>
> I'll look in this things too in next days, learning is always nice.
> Btw, about load/entry address, i have noticed a possible basic
> difference betweeen mcf5441x and mcf547x series:
>
> The second one (your cpu) is v4e and probably more recent i guess, and
> one major difference from datasheet seems to be that it is Harvard.
> So probably, for this reason, you can address ram from 0 there.
IIRC the 5475 was the first ColdFire with MMU, it is pretty old. Pretty
sure the 54411 came later. Not sure what the thinking was on the different
default memory layout though.
Regards
Greg
diff --git a/linux/mm/page_alloc.c b/linux/mm/page_alloc.c
index a2019fc..38bafc9 100644
--- a/linux/mm/page_alloc.c
+++ b/linux/mm/page_alloc.c
@@ -1178,6 +1178,7 @@ static void free_one_page(struct zone *zone,
static void __meminit __init_single_page(struct page *page, unsigned long pfn,
unsigned long zone, int nid)
{
+ printk("%s(%d): page=%p pfn=%ld\n", __FILE__, __LINE__, page, pfn);
set_page_links(page, zone, nid, pfn);
init_page_count(page);
page_mapcount_reset(page);
