sunxi: Enable non-secure access to RTC on sun6i (A31s)

On the A31s the RTC is by default secured. Thus when u-boot
loads the kernel in non-secure world, the RTC is unavailable. The
SoC has a TrustZone Protection Controller, which can be used to
enable non-secure access to the RTC.

On the A31 the TZPC doesn't seem to do anything, i.e. changes to
its register contents do not affect access to the RTC.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

arch/arm/cpu/armv7/sunxi/Makefile

@@ -28,6 +28,7 @@ obj-$(CONFIG_MACH_SUN6I)	+= clock_sun6i.o
 obj-$(CONFIG_MACH_SUN7I)	+= clock_sun4i.o
 obj-$(CONFIG_MACH_SUN8I)	+= clock_sun6i.o
 obj-$(CONFIG_MACH_SUN9I)	+= clock_sun9i.o
+obj-$(CONFIG_MACH_SUN6I)	+= tzpc.o
 
 obj-$(CONFIG_AXP152_POWER)	+= pmic_bus.o
 obj-$(CONFIG_AXP209_POWER)	+= pmic_bus.o

arch/arm/cpu/armv7/sunxi/board.c

@@ -23,6 +23,7 @@
 #include <asm/arch/gpio.h>
 #include <asm/arch/sys_proto.h>
 #include <asm/arch/timer.h>
+#include <asm/arch/tzpc.h>
 #include <asm/arch/mmc.h>
 
 #include <linux/compiler.h>
@@ -115,6 +116,10 @@ void s_init(void)
 		"orr r0, r0, #1 << 6\n"
 		"mcr p15, 0, r0, c1, c0, 1\n");
 #endif
+#if defined CONFIG_MACH_SUN6I
+	/* Enable non-secure access to the RTC */
+	tzpc_init();
+#endif
 
 	clock_init();
 	timer_init();

arch/arm/cpu/armv7/sunxi/tzpc.c

@@ -0,0 +1,18 @@
+/*
+ * (C) Copyright 2015 Chen-Yu Tsai <wens@csie.org>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <asm/io.h>
+#include <asm/arch/cpu.h>
+#include <asm/arch/tzpc.h>
+
+/* Configure Trust Zone Protection Controller */
+void tzpc_init(void)
+{
+	struct sunxi_tzpc *tzpc = (struct sunxi_tzpc *)SUNXI_TZPC_BASE;
+
+	/* Enable non-secure access to the RTC */
+	writel(SUNXI_TZPC_DECPORT0_RTC, &tzpc->decport0_set);
+}

arch/arm/include/asm/arch-sunxi/tzpc.h

@@ -0,0 +1,23 @@
+/*
+ * (C) Copyright 2015 Chen-Yu Tsai <wens@csie.org>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#ifndef _SUNXI_TZPC_H
+#define _SUNXI_TZPC_H
+
+#ifndef __ASSEMBLY__
+struct sunxi_tzpc {
+	u32 r0size;		/* 0x00 Size of secure RAM region */
+	u32 decport0_status;	/* 0x04 Status of decode protection port 0 */
+	u32 decport0_set;	/* 0x08 Set decode protection port 0 */
+	u32 decport0_clear;	/* 0x0c Clear decode protection port 0 */
+};
+#endif
+
+#define SUNXI_TZPC_DECPORT0_RTC	(1 << 1)
+
+void tzpc_init(void);
+
+#endif /* _SUNXI_TZPC_H */