Hello,
Background:
I want to create a script to recover an i-MX6 by doing:
1) setup DDR3 RAM
2) load a bootloader (here: barebox) into RAM
3) resume at $bootloader_start_address
For that to work I need to disable the MMU to get a fixed memory layout
and also to disable caches which seems to be necessary. I didn't find a
dedicated command to do that though, so I used:
arm mcr 15 0 1 0 0 [expr [arm mrc 15 0 1 0 0] & ~0xd]
which seems to work. But the problem now is that openocd's view about
the MMU doesn't change and so the load_image command fails with:
Debug: 1457 578 armv7a.c:160 armv7a_mmu_translate_va(): 1st lvl desc:
00000000
Error: 1458 578 armv7a.c:163 armv7a_mmu_translate_va(): Address
translation failure
I instrumented cortex_a8_write_memory and really cortex_a8_mmu(target,
&mmu_enabled) returns with mmu_enabled=1 even though the MMU is already
off. It seems
target_to_cortex_a8(target)->armv7a_common.armv7a_mmu.mmu_enabled
is only updated in cortex_a8_post_debug_entry which isn't called at the
end of the command disabling the MMU above.
I also tried:
# thats a 'b .'
mww phys 0x00900000 0xeafffffe
# disable MMU and caches
arm mcr 15 0 1 0 0 [expr [arm mrc 15 0 1 0 0] & ~0xd]
step 0x00900000
but this doesn't seem to be reliable. Sometimes it results in:
Error: timeout waiting for target halt
Sometimes (if Linux is already booted) makes Linux unhappy and printing:
Unable to handle kernel NULL pointer dereference at virtual address
00000000
on the machine's console.
Any ideas? Did I miss anything?
Best regards
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | http://www.pengutronix.de/ |
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