BACKPORT: arm64: move sp_el0 and tpidr_el1 into cpu_suspend_ctx

When returning from idle, we rely on the fact that thread_info lives at
the end of the kernel stack, and restore this by masking the saved stack
pointer. Subsequent patches will sever the relationship between the
stack and thread_info, and to cater for this we must save/restore sp_el0
explicitly, storing it in cpu_suspend_ctx.

As cpu_suspend_ctx must be doubleword aligned, this leaves us with an
extra slot in cpu_suspend_ctx. We can use this to save/restore tpidr_el1
in the same way, which simplifies the code, avoiding pointer chasing on
the restore path (as we no longer need to load thread_info::cpu followed
by the relevant slot in __per_cpu_offset based on this).

This patch stashes both registers in cpu_suspend_ctx.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Laura Abbott <labbott@redhat.com>
Cc: James Morse <james.morse@arm.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

This is a modification of Mark Rutland's original patch. The differences
from the original patch are as follows :-
	- NR_CTX_REGS is set to 13 instead of 12
	- x13 and x14 are used as temporary registers to hold sp_el0 and
	  tpidr_el1 instead of x11 and x12.
	- The values are temporarily stashed at offset 88 and 96 of
	  cpu_suspend_ctx instead of 80 and 88.

The original patch would not apply cleanly and these changes were made
to resolve this.

Bug: 38331309
Change-Id: I4e72aebd51e99d3767487383c14a1ba784312bf1
(cherry picked from commit 623b476fc815464a0241ea7483da7b3580b7d8ac)
Signed-off-by: Zubin Mithra <zsm@google.com>

arch/arm64/include/asm/suspend.h

@@ -1,7 +1,7 @@
 #ifndef __ASM_SUSPEND_H
 #define __ASM_SUSPEND_H
 
-#define NR_CTX_REGS 11
+#define NR_CTX_REGS 13
 
 /*
  * struct cpu_suspend_ctx must be 16-byte aligned since it is allocated on

arch/arm64/kernel/sleep.S

@@ -173,9 +173,6 @@ ENTRY(cpu_resume)
 	/* load physical address of identity map page table in x1 */
 	adrp	x1, idmap_pg_dir
 	mov	sp, x2
-	/* save thread_info */
-	and	x2, x2, #~(THREAD_SIZE - 1)
-	msr	sp_el0, x2
 	/*
 	 * cpu_do_resume expects x0 to contain context physical address
 	 * pointer and x1 to contain physical address of 1:1 page tables

arch/arm64/kernel/suspend.c

@@ -95,12 +95,6 @@ int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
 		 */
 		cpu_uninstall_idmap();
 
-		/*
-		 * Restore per-cpu offset before any kernel
-		 * subsystem relying on it has a chance to run.
-		 */
-		set_my_cpu_offset(per_cpu_offset(smp_processor_id()));
-
 		/*
 		 * PSTATE was not saved over suspend/resume, re-enable any
 		 * detected features that might not have been set correctly.

arch/arm64/mm/proc.S

@@ -71,12 +71,15 @@ ENTRY(cpu_do_suspend)
 	mrs	x10, mdscr_el1
 	mrs	x11, oslsr_el1
 	mrs	x12, sctlr_el1
+	mrs	x13, tpidr_el1
+	mrs	x14, sp_el0
 	stp	x2, x3, [x0]
 	stp	x4, x5, [x0, #16]
 	stp	x6, x7, [x0, #32]
 	stp	x8, x9, [x0, #48]
 	stp	x10, x11, [x0, #64]
-	str	x12, [x0, #80]
+	stp	x12, x13, [x0, #80]
+	str	x14, [x0, #96]
 	ret
 ENDPROC(cpu_do_suspend)
 
@@ -99,7 +102,8 @@ ENTRY(cpu_do_resume)
 	ldp	x6, x7, [x0, #32]
 	ldp	x8, x9, [x0, #48]
 	ldp	x10, x11, [x0, #64]
-	ldr	x12, [x0, #80]
+	ldp	x12, x13, [x0, #80]
+	ldr	x14, [x0, #96]
 	msr	tpidr_el0, x2
 	msr	tpidrro_el0, x3
 	msr	contextidr_el1, x4
@@ -111,6 +115,8 @@ ENTRY(cpu_do_resume)
 	msr	tcr_el1, x8
 	msr	vbar_el1, x9
 	msr	mdscr_el1, x10
+	msr	tpidr_el1, x13
+	msr	sp_el0, x14
 	/*
 	 * Restore oslsr_el1 by writing oslar_el1
 	 */