From 545f6950ae4dc55b4974986aa9629adb16eaf4e1 Mon Sep 17 00:00:00 2001
From: Jaxson Han <jaxson.han@arm.com>
Date: Tue, 25 May 2021 07:25:00 +0100
Subject: [PATCH] aarch64: Rename labels and prepare for lower EL booting

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.

Upstream-Status: Pending
Signed-off-by: Jaxson Han <jaxson.han@arm.com>
---
 arch/aarch64/boot.S | 28 ++++++++++++++++++++--------
 arch/aarch64/psci.S |  9 +++++----
 arch/aarch64/spin.S |  4 ++--
 3 files changed, 27 insertions(+), 14 deletions(-)

diff --git a/arch/aarch64/boot.S b/arch/aarch64/boot.S
index d682ba5..fab694e 100644
--- a/arch/aarch64/boot.S
+++ b/arch/aarch64/boot.S
@@ -34,18 +34,30 @@ ASM_FUNC(_start)
 
 	/*
 	 * 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
+	b.eq	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]
 
-	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
 
@@ -145,7 +157,7 @@ ASM_FUNC(_start)
 
 	bl	gic_secure_init
 
-	b	start_el3
+	b	start_el_max
 
 err_invalid_id:
 	b	.
@@ -172,7 +184,7 @@ ASM_FUNC(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
@@ -181,7 +193,7 @@ ASM_FUNC(jump_kernel)
 	mov	x3, x23
 
 	b.eq	1f
-	br	x19			// No EL3
+	br	x19			// Keep current EL
 
 1:	mov	x4, #SPSR_KERNEL
 
@@ -199,5 +211,5 @@ ASM_FUNC(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 8bd224b..7b8919a 100644
--- a/arch/aarch64/psci.S
+++ b/arch/aarch64/psci.S
@@ -79,7 +79,7 @@ smc_exit:
 	ldp	x18, x19, [sp], #16
 	eret
 
-ASM_FUNC(start_el3)
+ASM_FUNC(start_el_max)
 	ldr	x0, =vector
 	bl	setup_vector
 
@@ -89,10 +89,11 @@ ASM_FUNC(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 othersr
+ * will be trapped in an infinite loop.
  */
-ASM_FUNC(start_no_el3)
+ASM_FUNC(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 1ea1c0b..bfb1d47 100644
--- a/arch/aarch64/spin.S
+++ b/arch/aarch64/spin.S
@@ -12,8 +12,8 @@
 
 	.text
 
-ASM_FUNC(start_el3)
-ASM_FUNC(start_no_el3)
+ASM_FUNC(start_el_max)
+ASM_FUNC(start_keep_el)
 	cpuid	x0, x1
 	bl	find_logical_id