ARM: at91: add code to handle secure calls

Since OP-TEE now has a more complete support for sama5d2, add necessary
code to perform SMC calls. The detection of OP-TEE is based on a
specific device-tree node path (/firmware/optee) such has done by some
other SoC. A check is added to avoid doing SMC calls without having
OP-TEE.

Signed-off-by: Clément Léger <clement.leger@bootlin.com>
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>

Author: clementleger

arch/arm/mach-at91/Makefile

@@ -7,7 +7,7 @@
 obj-$(CONFIG_SOC_AT91RM9200)	+= at91rm9200.o
 obj-$(CONFIG_SOC_AT91SAM9)	+= at91sam9.o
 obj-$(CONFIG_SOC_SAM9X60)	+= sam9x60.o
-obj-$(CONFIG_SOC_SAMA5)		+= sama5.o
+obj-$(CONFIG_SOC_SAMA5)		+= sama5.o sam_secure.o
 obj-$(CONFIG_SOC_SAMA7)		+= sama7.o
 obj-$(CONFIG_SOC_SAMV7)		+= samv7.o
 

arch/arm/mach-at91/sam_secure.c

@@ -0,0 +1,46 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2022, Microchip
+ */
+
+#include <linux/arm-smccc.h>
+#include <linux/of.h>
+
+#include "sam_secure.h"
+
+static bool optee_available;
+
+#define SAM_SIP_SMC_STD_CALL_VAL(func_num) \
+	ARM_SMCCC_CALL_VAL(ARM_SMCCC_STD_CALL, ARM_SMCCC_SMC_32, \
+	ARM_SMCCC_OWNER_SIP, (func_num))
+
+struct arm_smccc_res sam_smccc_call(u32 fn, u32 arg0, u32 arg1)
+{
+	struct arm_smccc_res res = {.a0 = -1};
+
+	if (WARN_ON(!optee_available))
+		return res;
+
+	arm_smccc_smc(SAM_SIP_SMC_STD_CALL_VAL(fn), arg0, arg1, 0, 0, 0, 0, 0,
+		      &res);
+
+	return res;
+}
+
+void __init sam_secure_init(void)
+{
+	struct device_node *np;
+
+	/*
+	 * We only check that the OP-TEE node is present and available. The
+	 * OP-TEE kernel driver is not needed for the type of interaction made
+	 * with OP-TEE here so the driver's status is not checked.
+	 */
+	np = of_find_node_by_path("/firmware/optee");
+	if (np && of_device_is_available(np))
+		optee_available = true;
+	of_node_put(np);
+
+	if (optee_available)
+		pr_info("Running under OP-TEE firmware\n");
+}

arch/arm/mach-at91/sam_secure.h

@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2022, Microchip
+ */
+
+#ifndef SAM_SECURE_H
+#define SAM_SECURE_H
+
+#include <linux/arm-smccc.h>
+
+void __init sam_secure_init(void);
+struct arm_smccc_res sam_smccc_call(u32 fn, u32 arg0, u32 arg1);
+
+#endif /* SAM_SECURE_H */

arch/arm/mach-at91/sama5.c

@@ -14,6 +14,7 @@
 #include <asm/system_misc.h>
 
 #include "generic.h"
+#include "sam_secure.h"
 
 static void __init sama5_dt_device_init(void)
 {
@@ -47,6 +48,7 @@ MACHINE_END
 static void __init sama5d2_init(void)
 {
 	of_platform_default_populate(NULL, NULL, NULL);
+	sam_secure_init();
 	sama5d2_pm_init();
 }