Subject: [PATCH RFC v8 08/24] arm64: Initialize POR_EL1 register on cpu_resume()

From: Kevin Brodsky <[email-masked]>
Date: Tue, 26 May 2026 12:15:57 +0100

From: Yeoreum Yun <[email-masked]>

The POR_EL1 register is reset to an unknown value after cpu_suspend().
Since POR_EL1 always holds POR_EL1_INIT when entering cpu_suspend(),
initialize POR_EL1 with POR_EL1_INIT before cpu_do_resume().

Signed-off-by: Yeoreum Yun <[email-masked]>
Signed-off-by: Kevin Brodsky <[email-masked]>
---
 arch/arm64/kernel/sleep.S | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arch/arm64/kernel/sleep.S b/arch/arm64/kernel/sleep.S
index f093cdf71be1..e0a6ad85cd24 100644
--- a/arch/arm64/kernel/sleep.S
+++ b/arch/arm64/kernel/sleep.S
@@ -3,6 +3,7 @@
 #include <linux/linkage.h>
 #include <asm/asm-offsets.h>
 #include <asm/assembler.h>
+#include <asm/kpkeys.h>
 #include <asm/smp.h>
 
 	.text
@@ -134,6 +135,17 @@ SYM_FUNC_START(_cpu_resume)
 	/* load sp from context */
 	ldr	x2, [x0, #CPU_CTX_SP]
 	mov	sp, x2
+
+#ifdef CONFIG_ARM64_POE
+alternative_if_not ARM64_HAS_S1POE
+	b	.Lskip_por_set
+alternative_else_nop_endif
+	mov_q	x2, POR_EL1_INIT
+	msr_s	SYS_POR_EL1, x2
+	/* isb can be skipped since cpu_do_resume() will do it. */
+.Lskip_por_set:
+#endif /* CONFIG_ARM64_POE */
+
 	/*
 	 * cpu_do_resume expects x0 to contain context address pointer
 	 */

-- 
2.51.2