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