openwrt/package/boot/uboot-d1/patches/0026-sunxi-psci-Avoid-hanging-when-CPU-0-is-hot-unplugged.patch

From ca1e6f4491981432c3e88441131c8e25067da95e Mon Sep 17 00:00:00 2001
From: Samuel Holland <samuel@sholland.org>
Date: Sat, 9 Oct 2021 22:00:22 -0500
Subject: [PATCH 26/90] sunxi: psci: Avoid hanging when CPU 0 is hot-unplugged

Do not try to send an SGI from CPU 0 to itself. Since FIQs are masked
when entering monitor mode, this will hang. Plus, CPU 0 cannot fully
power itself off anyway. Instead, have it turn FIQs back on and continue
servicing SGIs from other cores.

Signed-off-by: Samuel Holland <samuel@sholland.org>
---
 arch/arm/cpu/armv7/sunxi/psci.c | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

--- a/arch/arm/cpu/armv7/sunxi/psci.c
+++ b/arch/arm/cpu/armv7/sunxi/psci.c
@@ -38,6 +38,15 @@
 #define SUN8I_R40_PWR_CLAMP(cpu)		(0x120 + (cpu) * 0x4)
 #define SUN8I_R40_SRAMC_SOFT_ENTRY_REG0		(0xbc)
 
+static inline u32 __secure cp15_read_mpidr(void)
+{
+	u32 val;
+
+	asm volatile ("mrc p15, 0, %0, c0, c0, 5" : "=r" (val));
+
+	return val;
+}
+
 static void __secure cp15_write_cntp_tval(u32 tval)
 {
 	asm volatile ("mcr p15, 0, %0, c14, c2, 0" : : "r" (tval));
@@ -281,9 +290,14 @@ s32 __secure psci_cpu_off(void)
 {
 	psci_cpu_off_common();
 
-	/* Ask CPU0 via SGI15 to pull the rug... */
-	writel(BIT(16) | 15, GICD_BASE + GICD_SGIR);
-	dsb();
+	if (cp15_read_mpidr() & 3) {
+		/* Ask CPU0 via SGI15 to pull the rug... */
+		writel(BIT(16) | 15, GICD_BASE + GICD_SGIR);
+		dsb();
+	} else {
+		/* Unmask FIQs to service SGI15. */
+		asm volatile ("cpsie f");
+	}
 
 	/* Wait to be turned off */
 	while (1)