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U-Boot PPC: Enable ppc440 FPU correctly

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* On ppc440, the FPU is implemented as an Auxiliary Processing Unit,
we must therefore enable sending commands to it,
in addition to setting the MSR bit.
This commit is contained in:
François Revol 2012-06-02 01:30:48 +02:00
parent b837149e73
commit cce9d8cf89
1 changed files with 13 additions and 1 deletions
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14
src/system/boot/platform/u-boot/arch/ppc/arch_cpu.cpp
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@ -8,6 +8,7 @@
#include "cpu.h"
#include "board_config.h"
#include <OS.h>
#include <boot/platform.h>
@ -44,7 +45,18 @@ check_cpu_features()
{
uint32 msr;
// we do need an FPU
#if BOARD_CPU_TYPE_PPC440
// the FPU is implemented as an Auxiliary Processing Unit,
// so we must enable transfers by setting the DAPUIB bit to 0
asm volatile(
"mfccr0 %%r3\n"
"\tlis %%r4,~(1<<(20-16))\n"
"\tand %%r3,%%r3,%%r4\n"
"\tmtccr0 %%r3"
: : : "r3", "r4");
#endif
// we do need an FPU for vsnprintf to work
// on Sam460ex at least U-Boot doesn't enable the FPU for us
msr = get_msr();
msr |= MSR_FP_AVAILABLE;