meta-arm/meta-arm-bsp/recipes-bsp/boot-wrapper-aarch64/files/fvp-baser-aemv8r64/0003-aarch64-Prepare-for-lower-EL-booting.patch

From 252cbd36e51414b60ab68306f9c38e358709494d 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: Prepare for lower EL booting

Save SPSR_KERNEL into spsr_to_elx during el3_init.
The jump_kernel will load spsr_to_elx into spsr_el3.

This change will make it easier to control whether drop to lower EL
before jumping to the kernel.

Upstream-Status: Pending
Signed-off-by: Jaxson Han <jaxson.han@arm.com>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
---
 arch/aarch64/boot.S | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/arch/aarch64/boot.S b/arch/aarch64/boot.S
index 5105b41..243198d 100644
--- a/arch/aarch64/boot.S
+++ b/arch/aarch64/boot.S
@@ -151,7 +151,16 @@ el3_init:
 	mov	x0, #ZCR_EL3_LEN_MAX		// SVE: Enable full vector len
 	msr	ZCR_EL3, x0			// for EL2.
 
-1:
+	/*
+	 * Save SPSR_KERNEL into spsr_to_elx.
+	 * The jump_kernel will load spsr_to_elx into spsr_el3
+	 */
+1:	mov	w0, #SPSR_KERNEL
+	ldr	x1, =spsr_to_elx
+	str	w0, [x1]
+	b	el_max_init
+
+el_max_init:
 	ldr	x0, =COUNTER_FREQ
 	msr	cntfrq_el0, x0
 
@@ -199,7 +208,7 @@ ASM_FUNC(jump_kernel)
 	b.eq	1f
 	br	x19			// Keep current EL
 
-1:	mov	x4, #SPSR_KERNEL
+1:	ldr	w4, spsr_to_elx
 
 	/*
 	 * If bit 0 of the kernel address is set, we're entering in AArch32
@@ -217,3 +226,5 @@ ASM_FUNC(jump_kernel)
 	.align 3
 flag_keep_el:
 	.long 0
+spsr_to_elx:
+	.long 0