linux.git/arch/mips/kernel/cpu-probe.c, branch v2.6.22

[MIPS] Fix scheduling latency issue on 24K, 34K and 74K cores

2007-07-06T15:17:11+00:00

The idle loop goes to sleep using the WAIT instruction if !need_resched().
This has is suffering from from a race condition that if if just after
need_resched has returned 0 an interrupt might set TIF_NEED_RESCHED but
we've just completed the test so go to sleep anyway.  This would be
trivial to fix by just disabling interrupts during that sequence as in:

        local_irq_disable();
        if (!need_resched())
                __asm__("wait");
        local_irq_enable();

but the processor architecture leaves it undefined if a processor calling
WAIT with interrupts disabled will ever restart its pipeline and indeed
some processors have made use of the freedom provided by the architecture
definition.  This has been resolved and the Config7.WII bit indicates that
the use of WAIT is safe on 24K, 24KE and 34K cores.  It also is safe on
74K starting revision 2.1.0 so enable the use of WAIT with interrupts
disabled for 74K based on a c0_prid of at least that.

Signed-off-by: Ralf Baechle

[MIPS] 20K: Handle WAIT related bugs according to errata information

2007-06-26T17:57:33+00:00

We used to avoid the WAIT entirely on the 20K but really only need to do
this on early revs of the 20K.  Without this a 20K was a bit of a
power hog.  Well, in the lower power power hog category ;-)

Signed-off-by: Ralf Baechle

[MIPS] Make some __setup functions static

2007-02-20T01:26:41+00:00

This fixes some sparse warnings. ("warning: symbol 'foo' was not
declared. Should it be static?")

Signed-off-by: Atsushi Nemoto 
Signed-off-by: Ralf Baechle

[MIPS] Include to for declaration of check_bugs32.

2007-02-18T21:31:36+00:00

Signed-off-by: Ralf Baechle

[MIPS] Whitespace cleanups.

2007-02-06T16:53:19+00:00

Signed-off-by: Ralf Baechle

[MIPS] Don't print presence of WAIT instruction on bootup.

2006-11-30T01:14:44+00:00

Not useful and quite a big of noise on bootup of large systems.

Signed-off-by: Ralf Baechle

[MIPS] Fix RM9000 wait instruction detection.

2006-10-09T22:20:45+00:00

Only revisions < 4.0 don't have a functional wait instruction.

From Thomas Koeller (Thomas.Koeller@baslerweb.com).

Signed-off-by: Ralf Baechle

[MIPS] Reduce race between cpu_wait() and need_resched() checking

2006-09-27T12:37:40+00:00

If a thread became runnable between need_resched() and the WAIT
instruction, switching to the thread will delay until a next interrupt.
Some CPUs can execute the WAIT instruction with interrupt disabled, so
we can get rid of this race on them (at least UP case).

Original Patch by Atsushi with fixing up for MIPS Technology's cores by
Ralf based on feedback from the RTL designers.

Signed-off-by: Atsushi Nemoto 
Signed-off-by: Ralf Baechle

[MIPS] Save 2k text size in cpu-probe

2006-07-13T20:26:01+00:00

The appended patch drops the inline for decode_configs, this saves about
2k of text size.

Signed-off-by: Thiemo Seufer 
Signed-off-by: Ralf Baechle

[MIPS] Uses MIPS_CONF_AR instead of magic constants.

2006-07-13T20:26:01+00:00

Signed-off-by: Thiemo Seufer 
Signed-off-by: Ralf Baechle