arm64: kernel: refactor the CPU suspend API for retention states

[cascardo/linux.git] / arch / arm64 / kernel / sleep.S

diff --git a/arch/arm64/kernel/sleep.S b/arch/arm64/kernel/sleep.S
index b192572..a564b44 100644 (file)
--- a/arch/arm64/kernel/sleep.S
+++ b/arch/arm64/kernel/sleep.S
@@ -49,28 +49,39 @@
        orr     \dst, \dst, \mask               // dst|=(aff3>>rs3)
        .endm
 /*
- * Save CPU state for a suspend.  This saves callee registers, and allocates
- * space on the kernel stack to save the CPU specific registers + some
- * other data for resume.
+ * Save CPU state for a suspend and execute the suspend finisher.
+ * On success it will return 0 through cpu_resume - ie through a CPU
+ * soft/hard reboot from the reset vector.
+ * On failure it returns the suspend finisher return value or force
+ * -EOPNOTSUPP if the finisher erroneously returns 0 (the suspend finisher
+ * is not allowed to return, if it does this must be considered failure).
+ * It saves callee registers, and allocates space on the kernel stack
+ * to save the CPU specific registers + some other data for resume.
  *
  *  x0 = suspend finisher argument
+ *  x1 = suspend finisher function pointer
  */
-ENTRY(__cpu_suspend)
+ENTRY(__cpu_suspend_enter)
        stp     x29, lr, [sp, #-96]!
        stp     x19, x20, [sp,#16]
        stp     x21, x22, [sp,#32]
        stp     x23, x24, [sp,#48]
        stp     x25, x26, [sp,#64]
        stp     x27, x28, [sp,#80]
+       /*
+        * Stash suspend finisher and its argument in x20 and x19
+        */
+       mov     x19, x0
+       mov     x20, x1
        mov     x2, sp
        sub     sp, sp, #CPU_SUSPEND_SZ // allocate cpu_suspend_ctx
-       mov     x1, sp
+       mov     x0, sp
        /*
-        * x1 now points to struct cpu_suspend_ctx allocated on the stack
+        * x0 now points to struct cpu_suspend_ctx allocated on the stack
         */
-       str     x2, [x1, #CPU_CTX_SP]
-       ldr     x2, =sleep_save_sp
-       ldr     x2, [x2, #SLEEP_SAVE_SP_VIRT]
+       str     x2, [x0, #CPU_CTX_SP]
+       ldr     x1, =sleep_save_sp
+       ldr     x1, [x1, #SLEEP_SAVE_SP_VIRT]
 #ifdef CONFIG_SMP
        mrs     x7, mpidr_el1
        ldr     x9, =mpidr_hash
@@ -82,11 +93,21 @@ ENTRY(__cpu_suspend)
        ldp     w3, w4, [x9, #MPIDR_HASH_SHIFTS]
        ldp     w5, w6, [x9, #(MPIDR_HASH_SHIFTS + 8)]
        compute_mpidr_hash x8, x3, x4, x5, x6, x7, x10
-       add     x2, x2, x8, lsl #3
+       add     x1, x1, x8, lsl #3
 #endif
-       bl      __cpu_suspend_finisher
+       bl      __cpu_suspend_save
+       /*
+        * Grab suspend finisher in x20 and its argument in x19
+        */
+       mov     x0, x19
+       mov     x1, x20
+       /*
+        * We are ready for power down, fire off the suspend finisher
+        * in x1, with argument in x0
+        */
+       blr     x1
         /*
-        * Never gets here, unless suspend fails.
+        * Never gets here, unless suspend finisher fails.
         * Successful cpu_suspend should return from cpu_resume, returning
         * through this code path is considered an error
         * If the return value is set to 0 force x0 = -EOPNOTSUPP
@@ -103,7 +124,7 @@ ENTRY(__cpu_suspend)
        ldp     x27, x28, [sp, #80]
        ldp     x29, lr, [sp], #96
        ret
-ENDPROC(__cpu_suspend)
+ENDPROC(__cpu_suspend_enter)
        .ltorg
 
 /*