[boot-wrapper PATCH v3 2/8] aarch64: Rename labels and prepare for lower EL booting

[Jaxson Han]

Prepare for booting from lower EL. Rename *_el3 relavant labels with
*_el_max and *_no_el3 with *_keep_el. Since the original _no_el3 means
"We neither do init sequence at this highest EL nor drop to lower EL
when entering to kernel", we rename it with _keep_el to make it more
clear for lower EL initialisation.

Signed-off-by: Jaxson Han <jaxson.han at arm.com>
---
 arch/aarch64/boot.S | 31 +++++++++++++++++++++----------
 arch/aarch64/psci.S | 13 +++++++------
 arch/aarch64/spin.S |  8 ++++----
 3 files changed, 32 insertions(+), 20 deletions(-)

diff --git a/arch/aarch64/boot.S b/arch/aarch64/boot.S
index a9264de..1a5da35 100644
--- a/arch/aarch64/boot.S
+++ b/arch/aarch64/boot.S
@@ -12,7 +12,7 @@
 	.section .init
 
 	.globl	_start
-	.globl jump_kernel
+	.globl	jump_kernel
 
 _start:
 	cpuid	x0, x1
@@ -22,20 +22,31 @@ _start:
 	bl	setup_stack
 
 	/*
-	 * EL3 initialisation
+	 * Boot sequence
+	 * If CurrentEL == EL3, then goto EL3 initialisation and drop to
+	 *   lower EL before entering the kernel.
+	 * Else, no initialisation and keep the current EL before
+	 *   entering the kernel.
 	 */
 	mrs	x0, CurrentEL
 	cmp	x0, #CURRENTEL_EL3
-	b.eq	1f
+	beq	el3_init
 
+	/*
+	 * We stay in the current EL for entering the kernel
+	 */
 	mov	w0, #1
-	ldr	x1, =flag_no_el3
+	ldr	x1, =flag_keep_el
 	str	w0, [x1]
 
 	bl	setup_stack
-	b	start_no_el3
+	b	start_keep_el
 
-1:	mov	x0, #0x30			// RES1
+	/*
+	 * EL3 initialisation
+	 */
+el3_init:
+	mov	x0, #0x30			// RES1
 	orr	x0, x0, #(1 << 0)		// Non-secure EL1
 	orr	x0, x0, #(1 << 8)		// HVC enable
 
@@ -114,7 +125,7 @@ _start:
 
 	bl	gic_secure_init
 
-	b	start_el3
+	b	start_el_max
 
 err_invalid_id:
 	b	.
@@ -141,7 +152,7 @@ jump_kernel:
 	bl	find_logical_id
 	bl	setup_stack		// Reset stack pointer
 
-	ldr	w0, flag_no_el3
+	ldr	w0, flag_keep_el
 	cmp	w0, #0			// Prepare Z flag
 
 	mov	x0, x20
@@ -150,7 +161,7 @@ jump_kernel:
 	mov	x3, x23
 
 	b.eq	1f
-	br	x19			// No EL3
+	br	x19			// Keep current EL
 
 1:	mov	x4, #SPSR_KERNEL
 
@@ -168,5 +179,5 @@ jump_kernel:
 
 	.data
 	.align 3
-flag_no_el3:
+flag_keep_el:
 	.long 0
diff --git a/arch/aarch64/psci.S b/arch/aarch64/psci.S
index 01ebe7d..ae02fd6 100644
--- a/arch/aarch64/psci.S
+++ b/arch/aarch64/psci.S
@@ -45,8 +45,8 @@ vector:
 
 	.text
 
-	.globl start_no_el3
-	.globl start_el3
+	.globl start_keep_el
+	.globl start_el_max
 
 err_exception:
 	b err_exception
@@ -101,7 +101,7 @@ smc_exit:
 	eret
 
 
-start_el3:
+start_el_max:
 	ldr	x0, =vector
 	bl	setup_vector
 
@@ -111,10 +111,11 @@ start_el3:
 	b	psci_first_spin
 
 /*
- * This PSCI implementation requires EL3. Without EL3 we'll only boot the
- * primary cpu, all others will be trapped in an infinite loop.
+ * This PSCI implementation requires the highest EL(EL3 or Armv8-R EL2).
+ * Without the highest EL, we'll only boot the primary cpu, all others
+ * will be trapped in an infinite loop.
  */
-start_no_el3:
+start_keep_el:
 	cpuid	x0, x1
 	bl	find_logical_id
 	cbz	x0, psci_first_spin
diff --git a/arch/aarch64/spin.S b/arch/aarch64/spin.S
index 72603cf..533177c 100644
--- a/arch/aarch64/spin.S
+++ b/arch/aarch64/spin.S
@@ -11,11 +11,11 @@
 
 	.text
 
-	.globl start_no_el3
-	.globl start_el3
+	.globl start_keep_el
+	.globl start_el_max
 
-start_el3:
-start_no_el3:
+start_el_max:
+start_keep_el:
 	cpuid	x0, x1
 	bl	find_logical_id
 
-- 
2.25.1