Commit e8db288e authored by Nicolas Pitre's avatar Nicolas Pitre
Browse files

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: default avatarNicolas Pitre <nico@linaro.org>
Reviewed-by: default avatarSantosh Shilimkar <santosh.shilimkar@ti.com>
Reviewed-by: default avatarWill Deacon <will.deacon@arm.com>
parent 0c91e7e0

arch/arm/Kconfig

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Original line number Diff line number Diff line
@@ -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

arch/arm/common/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -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

arch/arm/common/mcpm_entry.c

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Original line number Diff line number Diff line 
/*

 * 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]);

}

arch/arm/common/mcpm_head.S

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Original line number Diff line number Diff line 
/*

 * 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

arch/arm/include/asm/mcpm.h

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Original line number Diff line number Diff line 
/*

 * 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

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