openwrt/target/linux/mpc85xx/patches-6.6/150-arch-powerpc-simpleboot-prevent-overwrite-of-CPU1-sp.patch

From 5f856ccc34df25060d36a5a81b7b45b574d86e35 Mon Sep 17 00:00:00 2001
From: David Bauer <mail@david-bauer.net>
Date: Sun, 3 Dec 2023 20:09:24 +0100
Subject: [PATCH] arch: powerpc: simpleboot: prevent overwrite of CPU1
 spin-table

Don't overwrite the spin-table of additional CPU cores with loader-heap.

U-Boot places the spin-table for CPU1 on P1020 SoCs in the top 1MB of
system-memory. Instead of parsing reserved-memory (which would be
considerable more work), reduce the available system-memory for the
loader by 1MB.

This prevents the loader from overwriting the spin-table of
additional CPU cores on these platforms.

Linux itself needs to be made aware by this using reserved-memory
definitions.

This patch is required for using CPU1 on the Extreme Networks
WS-AP3825i.

Signed-off-by: David Bauer <mail@david-bauer.net>
---
 arch/powerpc/boot/simpleboot.c | 5 +++++
 1 file changed, 5 insertions(+)

--- a/arch/powerpc/boot/simpleboot.c
+++ b/arch/powerpc/boot/simpleboot.c
@@ -65,6 +65,11 @@ void platform_init(unsigned long r3, uns
 	if (sizeof(void *) == 4 && memsize64 >= 0x100000000ULL)
 		memsize64 = 0xffffffff;
 
+	/* Reserve upper 1 MB of memory for CPU1 spin-table */
+	if (memsize64 > 0x100000) {
+		memsize64 = memsize64 - 0x100000;
+	}
+
 	/* finally, setup the timebase */
 	node = fdt_node_offset_by_prop_value(_dtb_start, -1, "device_type",
 					     "cpu", sizeof("cpu"));