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Current implementation of cpu_{suspend}/cpu_{resume} relies on the MPIDR
to index the array of pointers where the context is saved and restored.
The current approach works as long as the MPIDR can be considered a
linear index, so that the pointers array can simply be dereferenced by
using the MPIDR[7:0] value.
On ARM multi-cluster systems, where the MPIDR may not be a linear index,
to properly dereference the stack pointer array, a mapping function should
be applied to it so that it can be used for arrays look-ups.
This patch adds code in the cpu_{suspend}/cpu_{resume} implementation
that relies on shifting and ORing hashing method to map a MPIDR value to a
set of buckets precomputed at boot to have a collision free mapping from
MPIDR to context pointers.
The hashing algorithm must be simple, fast, and implementable with few
instructions since in the cpu_resume path the mapping is carried out with
the MMU off and the I-cache off, hence code and data are fetched from DRAM
with no-caching available. Simplicity is counterbalanced with a little
increase of memory (allocated dynamically) for stack pointers buckets, that
should be anyway fairly limited on most systems.
Memory for context pointers is allocated in a early_initcall with
size precomputed and stashed previously in kernel data structures.
Memory for context pointers is allocated through kmalloc; this
guarantees contiguous physical addresses for the allocated memory which
is fundamental to the correct functioning of the resume mechanism that
relies on the context pointer array to be a chunk of contiguous physical
memory. Virtual to physical address conversion for the context pointer
array base is carried out at boot to avoid fiddling with virt_to_phys
conversions in the cpu_resume path which is quite fragile and should be
optimized to execute as few instructions as possible.
Virtual and physical context pointer base array addresses are stashed in a
struct that is accessible from assembly using values generated through the
asm-offsets.c mechanism.
Cc: Will Deacon <will.deacon@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Colin Cross <ccross@android.com>
Cc: Santosh Shilimkar <santosh.shilimkar@ti.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Amit Kucheria <amit.kucheria@linaro.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Nicolas Pitre <nico@linaro.org>
Tested-by: Shawn Guo <shawn.guo@linaro.org>
Tested-by: Kevin Hilman <khilman@linaro.org>
Tested-by: Stephen Warren <swarren@wwwdotorg.org>
166 lines
4.8 KiB
ArmAsm
166 lines
4.8 KiB
ArmAsm
#include <linux/linkage.h>
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#include <linux/threads.h>
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#include <asm/asm-offsets.h>
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#include <asm/assembler.h>
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#include <asm/glue-cache.h>
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#include <asm/glue-proc.h>
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.text
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/*
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* Implementation of MPIDR hash algorithm through shifting
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* and OR'ing.
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*
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* @dst: register containing hash result
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* @rs0: register containing affinity level 0 bit shift
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* @rs1: register containing affinity level 1 bit shift
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* @rs2: register containing affinity level 2 bit shift
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* @mpidr: register containing MPIDR value
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* @mask: register containing MPIDR mask
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*
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* Pseudo C-code:
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*
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*u32 dst;
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*
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*compute_mpidr_hash(u32 rs0, u32 rs1, u32 rs2, u32 mpidr, u32 mask) {
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* u32 aff0, aff1, aff2;
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* u32 mpidr_masked = mpidr & mask;
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* aff0 = mpidr_masked & 0xff;
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* aff1 = mpidr_masked & 0xff00;
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* aff2 = mpidr_masked & 0xff0000;
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* dst = (aff0 >> rs0 | aff1 >> rs1 | aff2 >> rs2);
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*}
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* Input registers: rs0, rs1, rs2, mpidr, mask
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* Output register: dst
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* Note: input and output registers must be disjoint register sets
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(eg: a macro instance with mpidr = r1 and dst = r1 is invalid)
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*/
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.macro compute_mpidr_hash dst, rs0, rs1, rs2, mpidr, mask
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and \mpidr, \mpidr, \mask @ mask out MPIDR bits
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and \dst, \mpidr, #0xff @ mask=aff0
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ARM( mov \dst, \dst, lsr \rs0 ) @ dst=aff0>>rs0
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THUMB( lsr \dst, \dst, \rs0 )
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and \mask, \mpidr, #0xff00 @ mask = aff1
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ARM( orr \dst, \dst, \mask, lsr \rs1 ) @ dst|=(aff1>>rs1)
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THUMB( lsr \mask, \mask, \rs1 )
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THUMB( orr \dst, \dst, \mask )
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and \mask, \mpidr, #0xff0000 @ mask = aff2
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ARM( orr \dst, \dst, \mask, lsr \rs2 ) @ dst|=(aff2>>rs2)
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THUMB( lsr \mask, \mask, \rs2 )
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THUMB( orr \dst, \dst, \mask )
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.endm
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/*
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* Save CPU state for a suspend. This saves the CPU general purpose
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* registers, and allocates space on the kernel stack to save the CPU
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* specific registers and some other data for resume.
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* r0 = suspend function arg0
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* r1 = suspend function
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*/
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ENTRY(__cpu_suspend)
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stmfd sp!, {r4 - r11, lr}
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#ifdef MULTI_CPU
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ldr r10, =processor
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ldr r4, [r10, #CPU_SLEEP_SIZE] @ size of CPU sleep state
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#else
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ldr r4, =cpu_suspend_size
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#endif
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mov r5, sp @ current virtual SP
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add r4, r4, #12 @ Space for pgd, virt sp, phys resume fn
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sub sp, sp, r4 @ allocate CPU state on stack
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stmfd sp!, {r0, r1} @ save suspend func arg and pointer
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add r0, sp, #8 @ save pointer to save block
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mov r1, r4 @ size of save block
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mov r2, r5 @ virtual SP
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ldr r3, =sleep_save_sp
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ldr r3, [r3, #SLEEP_SAVE_SP_VIRT]
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ALT_SMP(mrc p15, 0, r9, c0, c0, 5)
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ALT_UP_B(1f)
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ldr r8, =mpidr_hash
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/*
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* This ldmia relies on the memory layout of the mpidr_hash
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* struct mpidr_hash.
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*/
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ldmia r8, {r4-r7} @ r4 = mpidr mask (r5,r6,r7) = l[0,1,2] shifts
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compute_mpidr_hash lr, r5, r6, r7, r9, r4
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add r3, r3, lr, lsl #2
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1:
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bl __cpu_suspend_save
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adr lr, BSYM(cpu_suspend_abort)
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ldmfd sp!, {r0, pc} @ call suspend fn
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ENDPROC(__cpu_suspend)
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.ltorg
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cpu_suspend_abort:
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ldmia sp!, {r1 - r3} @ pop phys pgd, virt SP, phys resume fn
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teq r0, #0
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moveq r0, #1 @ force non-zero value
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mov sp, r2
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ldmfd sp!, {r4 - r11, pc}
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ENDPROC(cpu_suspend_abort)
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/*
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* r0 = control register value
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*/
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.align 5
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.pushsection .idmap.text,"ax"
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ENTRY(cpu_resume_mmu)
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ldr r3, =cpu_resume_after_mmu
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instr_sync
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mcr p15, 0, r0, c1, c0, 0 @ turn on MMU, I-cache, etc
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mrc p15, 0, r0, c0, c0, 0 @ read id reg
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instr_sync
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mov r0, r0
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mov r0, r0
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mov pc, r3 @ jump to virtual address
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ENDPROC(cpu_resume_mmu)
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.popsection
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cpu_resume_after_mmu:
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bl cpu_init @ restore the und/abt/irq banked regs
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mov r0, #0 @ return zero on success
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ldmfd sp!, {r4 - r11, pc}
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ENDPROC(cpu_resume_after_mmu)
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/*
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* Note: Yes, part of the following code is located into the .data section.
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* This is to allow sleep_save_sp to be accessed with a relative load
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* while we can't rely on any MMU translation. We could have put
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* sleep_save_sp in the .text section as well, but some setups might
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* insist on it to be truly read-only.
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*/
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.data
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.align
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ENTRY(cpu_resume)
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mov r1, #0
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ALT_SMP(mrc p15, 0, r0, c0, c0, 5)
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ALT_UP_B(1f)
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adr r2, mpidr_hash_ptr
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ldr r3, [r2]
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add r2, r2, r3 @ r2 = struct mpidr_hash phys address
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/*
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* This ldmia relies on the memory layout of the mpidr_hash
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* struct mpidr_hash.
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*/
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ldmia r2, { r3-r6 } @ r3 = mpidr mask (r4,r5,r6) = l[0,1,2] shifts
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compute_mpidr_hash r1, r4, r5, r6, r0, r3
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1:
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adr r0, _sleep_save_sp
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ldr r0, [r0, #SLEEP_SAVE_SP_PHYS]
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ldr r0, [r0, r1, lsl #2]
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setmode PSR_I_BIT | PSR_F_BIT | SVC_MODE, r1 @ set SVC, irqs off
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@ load phys pgd, stack, resume fn
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ARM( ldmia r0!, {r1, sp, pc} )
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THUMB( ldmia r0!, {r1, r2, r3} )
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THUMB( mov sp, r2 )
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THUMB( bx r3 )
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ENDPROC(cpu_resume)
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.align 2
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mpidr_hash_ptr:
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.long mpidr_hash - . @ mpidr_hash struct offset
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.type sleep_save_sp, #object
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ENTRY(sleep_save_sp)
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_sleep_save_sp:
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.space SLEEP_SAVE_SP_SZ @ struct sleep_save_sp
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