linux-kernel - Geode-GX1 processor in 2.6.21

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Message-Id: <200704301251.05697.juergen127@kreuzholzen.de>
Date:	Mon, 30 Apr 2007 12:51:05 +0200
From:	Juergen Beisert <juergen127@...uzholzen.de>
To:	linux-kernel@...r.kernel.org
Subject: Geode-GX1 processor in 2.6.21

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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