ARM: multi-cluster PM: secondary kernel entry code

CPUs in cluster based systems, such as big.LITTLE, have special needs
when entering the kernel due to a hotplug event, or when resuming from
a deep sleep mode.

This is vectorized so multiple CPUs can enter the kernel in parallel
without serialization.

The mcpm prefix stands for "multi cluster power management", however
this is usable on single cluster systems as well.  Only the basic
structure is introduced here.  This will be extended with later patches.

In order not to complexify things more than they currently have to,
the planned work to make runtime adjusted MPIDR based indexing and
dynamic memory allocation for cluster states is postponed to a later
cycle. The MAX_NR_CLUSTERS and MAX_CPUS_PER_CLUSTER static definitions
should be sufficient for those systems expected to be available in the
near future.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Reviewed-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Reviewed-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Nicolas Pitre 2012-04-12 02:45:22 -04:00
parent 0c91e7e07e
commit e8db288e05
5 changed files with 159 additions and 0 deletions

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@ -1599,6 +1599,14 @@ config HAVE_ARM_TWD
help
This options enables support for the ARM timer and watchdog unit
config MCPM
bool "Multi-Cluster Power Management"
depends on CPU_V7 && SMP
help
This option provides the common power management infrastructure
for (multi-)cluster based systems, such as big.LITTLE based
systems.
choice
prompt "Memory split"
default VMSPLIT_3G

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@ -11,3 +11,4 @@ obj-$(CONFIG_SHARP_PARAM) += sharpsl_param.o
obj-$(CONFIG_SHARP_SCOOP) += scoop.o
obj-$(CONFIG_PCI_HOST_ITE8152) += it8152.o
obj-$(CONFIG_ARM_TIMER_SP804) += timer-sp.o
obj-$(CONFIG_MCPM) += mcpm_head.o mcpm_entry.o

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@ -0,0 +1,22 @@
/*
* arch/arm/common/mcpm_entry.c -- entry point for multi-cluster PM
*
* Created by: Nicolas Pitre, March 2012
* Copyright: (C) 2012-2013 Linaro Limited
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <asm/mcpm.h>
#include <asm/cacheflush.h>
extern unsigned long mcpm_entry_vectors[MAX_NR_CLUSTERS][MAX_CPUS_PER_CLUSTER];
void mcpm_set_entry_vector(unsigned cpu, unsigned cluster, void *ptr)
{
unsigned long val = ptr ? virt_to_phys(ptr) : 0;
mcpm_entry_vectors[cluster][cpu] = val;
sync_cache_w(&mcpm_entry_vectors[cluster][cpu]);
}

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@ -0,0 +1,86 @@
/*
* arch/arm/common/mcpm_head.S -- kernel entry point for multi-cluster PM
*
* Created by: Nicolas Pitre, March 2012
* Copyright: (C) 2012-2013 Linaro Limited
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/linkage.h>
#include <asm/mcpm.h>
.macro pr_dbg string
#if defined(CONFIG_DEBUG_LL) && defined(DEBUG)
b 1901f
1902: .asciz "CPU"
1903: .asciz " cluster"
1904: .asciz ": \string"
.align
1901: adr r0, 1902b
bl printascii
mov r0, r9
bl printhex8
adr r0, 1903b
bl printascii
mov r0, r10
bl printhex8
adr r0, 1904b
bl printascii
#endif
.endm
.arm
.align
ENTRY(mcpm_entry_point)
THUMB( adr r12, BSYM(1f) )
THUMB( bx r12 )
THUMB( .thumb )
1:
mrc p15, 0, r0, c0, c0, 5 @ MPIDR
ubfx r9, r0, #0, #8 @ r9 = cpu
ubfx r10, r0, #8, #8 @ r10 = cluster
mov r3, #MAX_CPUS_PER_CLUSTER
mla r4, r3, r10, r9 @ r4 = canonical CPU index
cmp r4, #(MAX_CPUS_PER_CLUSTER * MAX_NR_CLUSTERS)
blo 2f
/* We didn't expect this CPU. Try to cheaply make it quiet. */
1: wfi
wfe
b 1b
2: pr_dbg "kernel mcpm_entry_point\n"
/*
* MMU is off so we need to get to mcpm_entry_vectors in a
* position independent way.
*/
adr r5, 3f
ldr r6, [r5]
add r6, r5, r6 @ r6 = mcpm_entry_vectors
mcpm_entry_gated:
ldr r5, [r6, r4, lsl #2] @ r5 = CPU entry vector
cmp r5, #0
wfeeq
beq mcpm_entry_gated
pr_dbg "released\n"
bx r5
.align 2
3: .word mcpm_entry_vectors - .
ENDPROC(mcpm_entry_point)
.bss
.align 5
.type mcpm_entry_vectors, #object
ENTRY(mcpm_entry_vectors)
.space 4 * MAX_NR_CLUSTERS * MAX_CPUS_PER_CLUSTER

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@ -0,0 +1,42 @@
/*
* arch/arm/include/asm/mcpm.h
*
* Created by: Nicolas Pitre, April 2012
* Copyright: (C) 2012-2013 Linaro Limited
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#ifndef MCPM_H
#define MCPM_H
/*
* Maximum number of possible clusters / CPUs per cluster.
*
* This should be sufficient for quite a while, while keeping the
* (assembly) code simpler. When this starts to grow then we'll have
* to consider dynamic allocation.
*/
#define MAX_CPUS_PER_CLUSTER 4
#define MAX_NR_CLUSTERS 2
#ifndef __ASSEMBLY__
/*
* Platform specific code should use this symbol to set up secondary
* entry location for processors to use when released from reset.
*/
extern void mcpm_entry_point(void);
/*
* This is used to indicate where the given CPU from given cluster should
* branch once it is ready to re-enter the kernel using ptr, or NULL if it
* should be gated. A gated CPU is held in a WFE loop until its vector
* becomes non NULL.
*/
void mcpm_set_entry_vector(unsigned cpu, unsigned cluster, void *ptr);
#endif /* ! __ASSEMBLY__ */
#endif