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Merge pull request #42 from ssvb/20160506-fel-sdboot-for-a64

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Make fel-sdboot.sunxi usable on A64 and A80

This also fixes potential problems with older SoCs when using certain (cross-)toolchains. See the discussion of #42
This commit is contained in:
NiteHawk 2016-05-13 07:35:40 +02:00
commit ce9cf33606
2 changed files with 20 additions and 1 deletions
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fel-sdboot.c
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@ -36,5 +36,24 @@ dd if=fel-boot.sunxi of=/dev/sdX bs=1024 seek=8
void _start(void)
{
((void (*)(void))0xffff0020)();
unsigned int sctlr;
/*
* FEL mode fails to activate in an unpredictable way without
* this NOP padding. Minor changes in the code, such as checking
* the PC register (PC >= 0x10000) instead of SCTLR.V or doing
* jump instead of call to the FEL handler in the BROM sometimes
* break on A64 and sometimes break on A10/A13/A20. Trying to
* add DSB & ISB instructions and/or invalidating caches and
* BTB do not seem to make any difference. Only adding a bunch
* of NOP instructions in the beginning helps.
*/
asm volatile(".rept 32 \n nop \n .endr");
asm volatile("mrc p15, 0, %0, c1, c0, 0" : "=r" (sctlr));
if (sctlr & (1 << 13)) /* SCTLR.V */
((void (*)(void))0xffff0020)();
else
((void (*)(void))0x00000020)();
}