[RFC PATCH v2] ARM hibernation / suspend-to-disk support code

[Frank Hofmann <frank.hofmann@tomtom.com>]

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On Mon, 23 May 2011, Russell King - ARM Linux wrote:

> On Mon, May 23, 2011 at 02:37:19PM +0100, Frank Hofmann wrote:
>> What I've found necessary to save/restore via swsusp_arch_suspend/resume
>> are the SYSTEM_MODE and SVC_MODE registers.
>> Yesterday, I had thought that cpu_init() resets SVC_MODE sufficiently but
>> that doesn't seem to be the case, if I leave that out, resume-from-disk
>> doesn't work anymore.
>
> You will be running in SVC mode, so the SVC mode registers are your
> current register set.  At some point you need to do an effective
> "context switch" between the kernel doing the resume and the kernel
> which was running.  That involves restoring the saved register state.
>
> System mode on the other hand is unused by the kernel.
>

Ah, and I had it the other way round ... that's why. Thanks !

I've tried that, saving/restoring just CPSR/SPSR and the reg set - and 
that seems sufficient, works fine !


All this means that the basic code has again become smaller.
Attached is a new version, integrating all the feedback so far:

* save/restore only those parts of the register set that the kernel cannot
   reinitialize from scratch

* take care of FIQ disable/enable bracketing

* use traditional stmfd/ldmfd instead of push/pop

* don't rely on thread state, current->active_mm, but use global &init_mm

* dump arch_prepare_suspend (skipping ahead of Rafael's suggested fix)

* ditch the vmlinux.lds changes as they're not needed


What other outstanding things are there to address for this ?

All the best,
FrankH.

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diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 6b6786c..859dd86 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -198,6 +198,9 @@ config VECTORS_BASE
 config ARCH_HAS_CPU_IDLE_WAIT
 	def_bool y
 
+config ARCH_HIBERNATION_POSSIBLE
+	def_bool n
+
 source "init/Kconfig"
 
 source "kernel/Kconfig.freezer"
diff --git a/arch/arm/include/asm/memory.h b/arch/arm/include/asm/memory.h
index 5421d82..23e93a6 100644
--- a/arch/arm/include/asm/memory.h
+++ b/arch/arm/include/asm/memory.h
@@ -191,6 +191,7 @@ static inline void *phys_to_virt(unsigned long x)
  */
 #define __pa(x)			__virt_to_phys((unsigned long)(x))
 #define __va(x)			((void *)__phys_to_virt((unsigned long)(x)))
+#define __pa_symbol(x)		__pa(RELOC_HIDE((unsigned long)(x),0))
 #define pfn_to_kaddr(pfn)	__va((pfn) << PAGE_SHIFT)
 
 /*
diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
index c9b00bb..541ac3a 100644
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -36,6 +36,7 @@ obj-$(CONFIG_ARM_THUMBEE)	+= thumbee.o
 obj-$(CONFIG_KGDB)		+= kgdb.o
 obj-$(CONFIG_ARM_UNWIND)	+= unwind.o
 obj-$(CONFIG_HAVE_TCM)		+= tcm.o
+obj-$(CONFIG_HIBERNATION)	+= cpu.o swsusp.o
 
 obj-$(CONFIG_CRUNCH)		+= crunch.o crunch-bits.o
 AFLAGS_crunch-bits.o		:= -Wa,-mcpu=ep9312
diff --git a/arch/arm/kernel/cpu.c b/arch/arm/kernel/cpu.c
new file mode 100644
index 0000000..0f1c31f
--- /dev/null
+++ b/arch/arm/kernel/cpu.c
@@ -0,0 +1,64 @@
+/*
+ * Hibernation support specific for ARM
+ *
+ * Derived from work on ARM hibernation support by:
+ *
+ * Ubuntu project, hibernation support for mach-dove
+ * Copyright (C) 2010 Nokia Corporation (Hiroshi Doyu)
+ * Copyright (C) 2010 Texas Instruments, Inc. (Teerth Reddy et al.)
+ *	https://lkml.org/lkml/2010/6/18/4
+ *	https://lists.linux-foundation.org/pipermail/linux-pm/2010-June/027422.html
+ *	https://patchwork.kernel.org/patch/96442/
+ *
+ * Copyright (C) 2006 Rafael J. Wysocki <rjw@sisk.pl>
+ *
+ * License terms: GNU General Public License (GPL) version 2
+ */
+
+#include <linux/mm.h>
+#include <linux/sched.h>
+#include <linux/suspend.h>
+#include <asm/tlbflush.h>
+
+extern const void __nosave_begin, __nosave_end;
+
+int pfn_is_nosave(unsigned long pfn)
+{
+	unsigned long nosave_begin_pfn = __pa_symbol(&__nosave_begin) >> PAGE_SHIFT;
+	unsigned long nosave_end_pfn = PAGE_ALIGN(__pa_symbol(&__nosave_end)) >> PAGE_SHIFT;
+
+	return (pfn >= nosave_begin_pfn) && (pfn < nosave_end_pfn);
+}
+
+void save_processor_state(void)
+{
+	flush_thread();
+	local_fiq_disable();
+}
+
+void restore_processor_state(void)
+{
+	local_flush_tlb_all();
+	local_fiq_enable();
+}
+
+u8 __swsusp_arch_ctx[PAGE_SIZE] __attribute__((aligned(PAGE_SIZE)));
+u8 __swsusp_resume_stk[PAGE_SIZE/2] __nosavedata;
+
+/*
+ * The framework loads the hibernation image into this linked list,
+ * for swsusp_arch_resume() to copy back to the proper destinations.
+ *
+ * To make this work if resume is triggered from initramfs, the
+ * pagetables need to be switched to allow writes to kernel mem.
+ */
+void notrace __swsusp_arch_restore_image(void)
+{
+	extern struct pbe *restore_pblist;
+	struct pbe *pbe;
+
+	cpu_switch_mm(__virt_to_phys(swapper_pg_dir), &init_mm);
+
+	for (pbe = restore_pblist; pbe; pbe = pbe->next)
+		copy_page(pbe->orig_address, pbe->address);
+}
diff --git a/arch/arm/kernel/swsusp.S b/arch/arm/kernel/swsusp.S
new file mode 100644
index 0000000..1fc0e33
--- /dev/null
+++ b/arch/arm/kernel/swsusp.S
@@ -0,0 +1,72 @@
+/*
+ * Hibernation support specific for ARM
+ *
+ * Based on work by:
+ *
+ * Ubuntu project, hibernation support for mach-dove,
+ * Copyright (C) 2010 Nokia Corporation (Hiroshi Doyu)
+ * Copyright (C) 2010 Texas Instruments, Inc. (Teerth Reddy et al.)
+ *	https://lkml.org/lkml/2010/6/18/4
+ *	https://lists.linux-foundation.org/pipermail/linux-pm/2010-June/027422.html
+ *	https://patchwork.kernel.org/patch/96442/
+ *
+ * Copyright (C) 2006 Rafael J. Wysocki <rjw@sisk.pl>
+ *
+ * License terms: GNU General Public License (GPL) version 2
+ */
+
+#include <linux/linkage.h>
+#include <asm/memory.h>
+#include <asm/page.h>
+
+/*
+ * Save the current CPU state before suspend / poweroff.
+ */
+ENTRY(swsusp_arch_suspend)
+	ldr	r0, =__swsusp_arch_ctx
+	mrs	r1, cpsr
+	mrs	r2, spsr
+	stmia	r0!, {r1-r11,lr}	@ CPSR, SPSR, nonvolatile regs
+	str	sp, [r0], #4		@ stack
+	stmfd	sp!, {lr}
+	bl	__save_processor_state	@ machine-specific state
+	ldmfd	sp!, {lr}
+	b	swsusp_save		@ let framework write snapshot out
+ENDPROC(swsusp_arch_suspend)
+
+/*
+ * Restore the memory image from the pagelists, and load the CPU registers
+ * from saved state.
+ */
+ENTRY(swsusp_arch_resume)
+	/*
+	 * Switch stack to a nosavedata region to make sure image restore
+	 * doesn't clobber it underneath itself.
+	 */
+	ldr	sp, =(__swsusp_resume_stk + PAGE_SIZE / 2)
+	bl	__swsusp_arch_restore_image
+
+	/*
+	 * Restore the CPU registers.
+	 */
+	ldr	r0, =__swsusp_arch_ctx
+	ldmia	r0!, {r1,r2}		@ CPSR / SPSR
+	msr	cpsr, r1
+	msr	spsr, r2
+	ldr	r0, =__swsusp_arch_ctx	@ reload in case regset switched
+	ldmia	r0!, {r1-r11,lr}	@ nonvolatile regs
+	ldr	sp, [r0], #4		@ stack
+
+	/*
+	 * From here on we have a valid stack again. Core state is
+	 * not restored yet, redirect to the machine-specific
+	 * implementation to get that done.
+	 * Resume has succeeded at this point; if the machine-specific
+	 * code wants to fail it needs to panic.
+	 */
+	mov	r1, #0
+	stmfd	sp!, {r1,lr}
+	bl	__restore_processor_state	@ machine-specific state
+	bl	cpu_init			@ reinitialize other modes
+	ldmfd	sp!, {r0,pc}
+ENDPROC(swsusp_arch_resume)

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