Geode-GX1 processor in 2.6.21

From: Juergen Beisert
Date: Mon Apr 30 2007 - 06:51:28 EST


Hi all,

I do not understand it, but setting up some chipset features (tweaks) fail on
Geode GX1.

In arch/i386/kernel/cpu/cyrix.c function geode_configure() tries to enable
the "suspend on halt power saving feature". This is the line:

setCx86(CX86_CCR2, getCx86(CX86_CCR2) | 0x88);

If this register is 0x00 before, it is still 0x00 after this line. If I change
the line into this:

ccr2 = getCx86(CX86_CCR2);
ccr2 |= 0x88;
setCx86(CX86_CCR2, ccr2);

register ccr2 is 0x88 after the setCx86 call and the power saving feature is
active (and BTW: the TSC is useless then, because it also stops when the CPU
runs into a HLT instruction).

setCx86 and getCx86 are macros defined in include/asm-i386/processor.h:

#define getCx86(reg) ({ outb((reg), 0x22); inb(0x23); })

#define setCx86(reg, data) do { \
outb((reg), 0x22); \
outb((data), 0x23); \
} while (0)

Maybe the compiler does the wrong thing if someone uses these macros in the
same instruction?

Regards
Juergen
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