arm: v7R: Add support for MPU

The Memory Protection Unit(MPU) allows to partition memory into regions
and set individual protection attributes for each region. In absence
of MPU a default map[1] will take effect. Add support for configuring
MPU on Cortex-R, by reusing the existing support for Cortex-M processor.

[1] http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0460d/I1002400.html

Tested-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>

1 files changed, 108 insertions, 0 deletions

diff --git a/arch/arm/cpu/armv7/mpu_v7r.c b/arch/arm/cpu/armv7/mpu_v7r.c
new file mode 100644
index 0000000000..567d913414
--- /dev/null
+++ b/arch/arm/cpu/armv7/mpu_v7r.c
@@ -0,0 +1,108 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Cortex-R Memory Protection Unit specific code
+ *
+ * Copyright (C) 2018 Texas Instruments Incorporated - http://www.ti.com/
+ *	Lokesh Vutla <lokeshvutla@ti.com>
+ */
+
+#include <common.h>
+#include <command.h>
+#include <asm/armv7.h>
+#include <asm/system.h>
+#include <asm/barriers.h>
+#include <linux/compiler.h>
+
+#include <asm/armv7_mpu.h>
+
+/* MPU Type register definitions */
+#define MPUIR_S_SHIFT		0
+#define MPUIR_S_MASK		BIT(MPUIR_S_SHIFT)
+#define MPUIR_DREGION_SHIFT	8
+#define MPUIR_DREGION_MASK	(0xff << 8)
+
+/**
+ * Note:
+ * The Memory Protection Unit(MPU) allows to partition memory into regions
+ * and set individual protection attributes for each region. In absence
+ * of MPU a default map[1] will take effect. make sure to run this code
+ * from a region which has execution permissions by default.
+ * [1] http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0460d/I1002400.html
+ */
+
+void disable_mpu(void)
+{
+	u32 reg;
+
+	reg = get_cr();
+	reg &= ~CR_M;
+	dsb();
+	set_cr(reg);
+	isb();
+}
+
+void enable_mpu(void)
+{
+	u32 reg;
+
+	reg = get_cr();
+	reg |= CR_M;
+	dsb();
+	set_cr(reg);
+	isb();
+}
+
+int mpu_enabled(void)
+{
+	return get_cr() & CR_M;
+}
+
+void mpu_config(struct mpu_region_config *rgn)
+{
+	u32 attr, val;
+
+	attr = get_attr_encoding(rgn->mr_attr);
+
+	/* MPU Region Number Register */
+	asm volatile ("mcr p15, 0, %0, c6, c2, 0" : : "r" (rgn->region_no));
+
+	/* MPU Region Base Address Register */
+	asm volatile ("mcr p15, 0, %0, c6, c1, 0" : : "r" (rgn->start_addr));
+
+	/* MPU Region Size and Enable Register */
+	if (rgn->reg_size)
+		val = (rgn->reg_size << REGION_SIZE_SHIFT) | ENABLE_REGION;
+	else
+		val = DISABLE_REGION;
+	asm volatile ("mcr p15, 0, %0, c6, c1, 2" : : "r" (val));
+
+	/* MPU Region Access Control Register */
+	val = rgn->xn << XN_SHIFT | rgn->ap << AP_SHIFT | attr;
+	asm volatile ("mcr p15, 0, %0, c6, c1, 4" : : "r" (val));
+}
+
+void setup_mpu_regions(struct mpu_region_config *rgns, u32 num_rgns)
+{
+	u32 num, i;
+
+	asm volatile ("mrc p15, 0, %0, c0, c0, 4" : "=r" (num));
+	num = (num & MPUIR_DREGION_MASK) >> MPUIR_DREGION_SHIFT;
+	/* Regions to be configured cannot be greater than available regions */
+	if (num < num_rgns)
+		num_rgns = num;
+	/**
+	 * Assuming dcache might not be enabled at this point, disabling
+	 * and invalidating only icache.
+	 */
+	icache_disable();
+	invalidate_icache_all();
+
+	disable_mpu();
+
+	for (i = 0; i < num_rgns; i++)
+		mpu_config(&rgns[i]);
+
+	enable_mpu();
+
+	icache_enable();
+}