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author | Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> | 2013-05-16 10:34:30 +0100 |
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committer | Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> | 2013-06-20 11:24:11 +0100 |
commit | 7604537bbb5720376e8c9e6bc74a8e6305e3094d (patch) | |
tree | d832833f3217e04eac90b0be1c9359ace9763d7a /arch/arm/kernel | |
parent | 8cf72172d739639f2699131821a3ebc291287cf2 (diff) | |
download | linux-7604537bbb5720376e8c9e6bc74a8e6305e3094d.tar.gz linux-7604537bbb5720376e8c9e6bc74a8e6305e3094d.tar.bz2 linux-7604537bbb5720376e8c9e6bc74a8e6305e3094d.zip |
ARM: kernel: implement stack pointer save array through MPIDR hashing
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>
Diffstat (limited to 'arch/arm/kernel')
-rw-r--r-- | arch/arm/kernel/asm-offsets.c | 6 | ||||
-rw-r--r-- | arch/arm/kernel/sleep.S | 97 | ||||
-rw-r--r-- | arch/arm/kernel/suspend.c | 20 |
3 files changed, 105 insertions, 18 deletions
diff --git a/arch/arm/kernel/asm-offsets.c b/arch/arm/kernel/asm-offsets.c index ee68cce6b48e..ded041711beb 100644 --- a/arch/arm/kernel/asm-offsets.c +++ b/arch/arm/kernel/asm-offsets.c @@ -23,6 +23,7 @@ #include <asm/thread_info.h> #include <asm/memory.h> #include <asm/procinfo.h> +#include <asm/suspend.h> #include <asm/hardware/cache-l2x0.h> #include <linux/kbuild.h> @@ -145,6 +146,11 @@ int main(void) #ifdef MULTI_CACHE DEFINE(CACHE_FLUSH_KERN_ALL, offsetof(struct cpu_cache_fns, flush_kern_all)); #endif +#ifdef CONFIG_ARM_CPU_SUSPEND + DEFINE(SLEEP_SAVE_SP_SZ, sizeof(struct sleep_save_sp)); + DEFINE(SLEEP_SAVE_SP_PHYS, offsetof(struct sleep_save_sp, save_ptr_stash_phys)); + DEFINE(SLEEP_SAVE_SP_VIRT, offsetof(struct sleep_save_sp, save_ptr_stash)); +#endif BLANK(); DEFINE(DMA_BIDIRECTIONAL, DMA_BIDIRECTIONAL); DEFINE(DMA_TO_DEVICE, DMA_TO_DEVICE); diff --git a/arch/arm/kernel/sleep.S b/arch/arm/kernel/sleep.S index 987dcf33415c..db1536b8b30b 100644 --- a/arch/arm/kernel/sleep.S +++ b/arch/arm/kernel/sleep.S @@ -7,6 +7,49 @@ .text /* + * Implementation of MPIDR hash algorithm through shifting + * and OR'ing. + * + * @dst: register containing hash result + * @rs0: register containing affinity level 0 bit shift + * @rs1: register containing affinity level 1 bit shift + * @rs2: register containing affinity level 2 bit shift + * @mpidr: register containing MPIDR value + * @mask: register containing MPIDR mask + * + * Pseudo C-code: + * + *u32 dst; + * + *compute_mpidr_hash(u32 rs0, u32 rs1, u32 rs2, u32 mpidr, u32 mask) { + * u32 aff0, aff1, aff2; + * u32 mpidr_masked = mpidr & mask; + * aff0 = mpidr_masked & 0xff; + * aff1 = mpidr_masked & 0xff00; + * aff2 = mpidr_masked & 0xff0000; + * dst = (aff0 >> rs0 | aff1 >> rs1 | aff2 >> rs2); + *} + * Input registers: rs0, rs1, rs2, mpidr, mask + * Output register: dst + * Note: input and output registers must be disjoint register sets + (eg: a macro instance with mpidr = r1 and dst = r1 is invalid) + */ + .macro compute_mpidr_hash dst, rs0, rs1, rs2, mpidr, mask + and \mpidr, \mpidr, \mask @ mask out MPIDR bits + and \dst, \mpidr, #0xff @ mask=aff0 + ARM( mov \dst, \dst, lsr \rs0 ) @ dst=aff0>>rs0 + THUMB( lsr \dst, \dst, \rs0 ) + and \mask, \mpidr, #0xff00 @ mask = aff1 + ARM( orr \dst, \dst, \mask, lsr \rs1 ) @ dst|=(aff1>>rs1) + THUMB( lsr \mask, \mask, \rs1 ) + THUMB( orr \dst, \dst, \mask ) + and \mask, \mpidr, #0xff0000 @ mask = aff2 + ARM( orr \dst, \dst, \mask, lsr \rs2 ) @ dst|=(aff2>>rs2) + THUMB( lsr \mask, \mask, \rs2 ) + THUMB( orr \dst, \dst, \mask ) + .endm + +/* * Save CPU state for a suspend. This saves the CPU general purpose * registers, and allocates space on the kernel stack to save the CPU * specific registers and some other data for resume. @@ -29,12 +72,18 @@ ENTRY(__cpu_suspend) mov r1, r4 @ size of save block mov r2, r5 @ virtual SP ldr r3, =sleep_save_sp -#ifdef CONFIG_SMP - ALT_SMP(mrc p15, 0, lr, c0, c0, 5) - ALT_UP(mov lr, #0) - and lr, lr, #15 + ldr r3, [r3, #SLEEP_SAVE_SP_VIRT] + ALT_SMP(mrc p15, 0, r9, c0, c0, 5) + ALT_UP_B(1f) + ldr r8, =mpidr_hash + /* + * This ldmia relies on the memory layout of the mpidr_hash + * struct mpidr_hash. + */ + ldmia r8, {r4-r7} @ r4 = mpidr mask (r5,r6,r7) = l[0,1,2] shifts + compute_mpidr_hash lr, r5, r6, r7, r9, r4 add r3, r3, lr, lsl #2 -#endif +1: bl __cpu_suspend_save adr lr, BSYM(cpu_suspend_abort) ldmfd sp!, {r0, pc} @ call suspend fn @@ -81,15 +130,23 @@ ENDPROC(cpu_resume_after_mmu) .data .align ENTRY(cpu_resume) -#ifdef CONFIG_SMP - adr r0, sleep_save_sp - ALT_SMP(mrc p15, 0, r1, c0, c0, 5) - ALT_UP(mov r1, #0) - and r1, r1, #15 - ldr r0, [r0, r1, lsl #2] @ stack phys addr -#else - ldr r0, sleep_save_sp @ stack phys addr -#endif + mov r1, #0 + ALT_SMP(mrc p15, 0, r0, c0, c0, 5) + ALT_UP_B(1f) + adr r2, mpidr_hash_ptr + ldr r3, [r2] + add r2, r2, r3 @ r2 = struct mpidr_hash phys address + /* + * This ldmia relies on the memory layout of the mpidr_hash + * struct mpidr_hash. + */ + ldmia r2, { r3-r6 } @ r3 = mpidr mask (r4,r5,r6) = l[0,1,2] shifts + compute_mpidr_hash r1, r4, r5, r6, r0, r3 +1: + adr r0, _sleep_save_sp + ldr r0, [r0, #SLEEP_SAVE_SP_PHYS] + ldr r0, [r0, r1, lsl #2] + setmode PSR_I_BIT | PSR_F_BIT | SVC_MODE, r1 @ set SVC, irqs off @ load phys pgd, stack, resume fn ARM( ldmia r0!, {r1, sp, pc} ) @@ -98,7 +155,11 @@ THUMB( mov sp, r2 ) THUMB( bx r3 ) ENDPROC(cpu_resume) -sleep_save_sp: - .rept CONFIG_NR_CPUS - .long 0 @ preserve stack phys ptr here - .endr + .align 2 +mpidr_hash_ptr: + .long mpidr_hash - . @ mpidr_hash struct offset + + .type sleep_save_sp, #object +ENTRY(sleep_save_sp) +_sleep_save_sp: + .space SLEEP_SAVE_SP_SZ @ struct sleep_save_sp diff --git a/arch/arm/kernel/suspend.c b/arch/arm/kernel/suspend.c index 38a50676213b..41cf3cbf756d 100644 --- a/arch/arm/kernel/suspend.c +++ b/arch/arm/kernel/suspend.c @@ -1,9 +1,12 @@ #include <linux/init.h> +#include <linux/slab.h> +#include <asm/cacheflush.h> #include <asm/idmap.h> #include <asm/pgalloc.h> #include <asm/pgtable.h> #include <asm/memory.h> +#include <asm/smp_plat.h> #include <asm/suspend.h> #include <asm/tlbflush.h> @@ -82,3 +85,20 @@ void __cpu_suspend_save(u32 *ptr, u32 ptrsz, u32 sp, u32 *save_ptr) outer_clean_range(virt_to_phys(save_ptr), virt_to_phys(save_ptr) + sizeof(*save_ptr)); } + +extern struct sleep_save_sp sleep_save_sp; + +static int cpu_suspend_alloc_sp(void) +{ + void *ctx_ptr; + /* ctx_ptr is an array of physical addresses */ + ctx_ptr = kcalloc(mpidr_hash_size(), sizeof(u32), GFP_KERNEL); + + if (WARN_ON(!ctx_ptr)) + return -ENOMEM; + sleep_save_sp.save_ptr_stash = ctx_ptr; + sleep_save_sp.save_ptr_stash_phys = virt_to_phys(ctx_ptr); + sync_cache_w(&sleep_save_sp); + return 0; +} +early_initcall(cpu_suspend_alloc_sp); |