f39224a8c1
We weren't using the recommended sequence for putting the CPU into nap mode. When I changed the idle loop, for some reason 7447A cpus started hanging when we put them into nap mode. Changing to the recommended sequence fixes that. The complexity here is that the recommended sequence is a loop that keeps putting the cpu back into nap mode. Clearly we need some way to break out of the loop when an interrupt (external interrupt, decrementer, performance monitor) occurs. Here we use a bit in the thread_info struct to indicate that we need this, and the exception entry code notices this and arranges for the exception to return to the value in the link register, thus breaking out of the loop. We use a new `local_flags' field in the thread_info which we can alter without needing to use an atomic update sequence. The PPC970 has the same recommended sequence, so we do the same thing there too. This also fixes a bug in the kernel stack overflow handling code on 32-bit, since it was causing a value that we needed in a register to get trashed. Signed-off-by: Paul Mackerras <paulus@samba.org>
50 lines
1.2 KiB
ArmAsm
50 lines
1.2 KiB
ArmAsm
/*
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* This file contains the power_save function for 970-family CPUs.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/config.h>
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#include <linux/threads.h>
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#include <asm/processor.h>
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#include <asm/page.h>
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#include <asm/cputable.h>
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#include <asm/thread_info.h>
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#include <asm/ppc_asm.h>
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#include <asm/asm-offsets.h>
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#undef DEBUG
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.text
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_GLOBAL(power4_idle)
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BEGIN_FTR_SECTION
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blr
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END_FTR_SECTION_IFCLR(CPU_FTR_CAN_NAP)
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/* Now check if user or arch enabled NAP mode */
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LOAD_REG_ADDRBASE(r3,powersave_nap)
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lwz r4,ADDROFF(powersave_nap)(r3)
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cmpwi 0,r4,0
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beqlr
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/* Go to NAP now */
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BEGIN_FTR_SECTION
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DSSALL
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sync
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END_FTR_SECTION_IFSET(CPU_FTR_ALTIVEC)
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clrrdi r9,r1,THREAD_SHIFT /* current thread_info */
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ld r8,TI_LOCAL_FLAGS(r9) /* set napping bit */
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ori r8,r8,_TLF_NAPPING /* so when we take an exception */
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std r8,TI_LOCAL_FLAGS(r9) /* it will return to our caller */
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mfmsr r7
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ori r7,r7,MSR_EE
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oris r7,r7,MSR_POW@h
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1: sync
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isync
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mtmsrd r7
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isync
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b 1b
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