From c399283c71e310e1573e8d27f9cb9d27a4ea3376 Mon Sep 17 00:00:00 2001
From: Andrew Turner <andrew@FreeBSD.org>
Date: Mon, 20 Dec 2021 13:42:15 +0000
Subject: [PATCH] Add an loader command on arm64 to sync the cache

On boot we don't need to perform any CPU cache management when the IDC
and DIC fields in the ctr_el0 register are set. Add a command to tell
loader to ignore these fields. This could be useful, for example, if the
hardware is misreporting the values and we are missing a quirk to enable
it.

It is not expected this will be needed, but is only intended as a
workaround to ensure the kernel can still boot.

Sponsored by:	The FreeBSD Foundation
---
 stand/arm64/libarm64/cache.c | 38 ++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/stand/arm64/libarm64/cache.c b/stand/arm64/libarm64/cache.c
index ff52572399ac..105e08cb4257 100644
--- a/stand/arm64/libarm64/cache.c
+++ b/stand/arm64/libarm64/cache.c
@@ -37,17 +37,30 @@ __FBSDID("$FreeBSD$");
 #include <stand.h>
 #include <efi.h>
 
+#include "bootstrap.h"
 #include "cache.h"
 
+static long cache_flags;
+#define	CACHE_FLAG_DIC_OFF	(1<<0)
+#define	CACHE_FLAG_IDC_OFF	(1<<1)
+
 static bool
 get_cache_dic(uint64_t ctr)
 {
+	if ((cache_flags & CACHE_FLAG_DIC_OFF) != 0) {
+		return (false);
+	}
+
 	return (CTR_DIC_VAL(ctr) != 0);
 }
 
 static bool
 get_cache_idc(uint64_t ctr)
 {
+	if ((cache_flags & CACHE_FLAG_IDC_OFF) != 0) {
+		return (false);
+	}
+
 	return (CTR_IDC_VAL(ctr) != 0);
 }
 
@@ -112,3 +125,28 @@ cpu_inval_icache(void)
 		    : : : "memory");
 	}
 }
+
+static int
+command_cache_flags(int argc, char *argv[])
+{
+	char *cp;
+	long new_flags;
+
+	if (argc == 3) {
+		if (strcmp(argv[1], "set") == 0) {
+			new_flags = strtol(argv[2], &cp, 0);
+			if (cp[0] != '\0') {
+				printf("Invalid flags\n");
+			} else {
+				printf("Setting cache flags to %#lx\n",
+				    new_flags);
+				cache_flags = new_flags;
+				return (CMD_OK);
+			}
+		}
+	}
+
+	printf("usage: cache_flags set <value>\n");
+	return (CMD_ERROR);
+}
+COMMAND_SET(cache_flags, "cache_flags", "Set cache flags", command_cache_flags);