arm: stm32mp: Implement support for TZC 400 controller

The purpose of this change is to allow configuring TrustZone (TZC)
memory permissions. For example, OP-TEE expects TZC regions to be
configured in a very particular way. The API presented here is
intended to allow exactly that.

UCLASS support is not implemented, because it would not be too useful.
Changing TZC permissions needs to be done with care, so as not to cut
off access to memory we are currently using. One place where we can
use this is at the end of SPL, right before jumping to OP-TEE.

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Reviewed-by: Patrick Delaunay <patrick.delaunay@foss.st.com>

3 files changed, 170 insertions, 0 deletions

diff --git a/arch/arm/mach-stm32mp/Makefile b/arch/arm/mach-stm32mp/Makefile
index aa39867080..879c1961fe 100644
--- a/arch/arm/mach-stm32mp/Makefile
+++ b/arch/arm/mach-stm32mp/Makefile
@@ -10,6 +10,7 @@ obj-y += bsec.o
 
 ifdef CONFIG_SPL_BUILD
 obj-y += spl.o
+obj-y += tzc400.o
 else
 obj-y += cmd_stm32prog/
 obj-$(CONFIG_CMD_STM32KEY) += cmd_stm32key.o
diff --git a/arch/arm/mach-stm32mp/include/mach/tzc.h b/arch/arm/mach-stm32mp/include/mach/tzc.h
new file mode 100644
index 0000000000..16db55c464
--- /dev/null
+++ b/arch/arm/mach-stm32mp/include/mach/tzc.h
@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Simple API for configuring TrustZone memory regions
+ *
+ * The premise is that the desired TZC layout is known beforehand, and it can
+ * be configured in one step. tzc_configure() provides this functionality.
+ */
+#ifndef MACH_TZC_H
+#define MACH_TZC_H
+
+#include <linux/types.h>
+
+enum tzc_sec_mode {
+	TZC_ATTR_SEC_NONE = 0,
+	TZC_ATTR_SEC_R = 1,
+	TZC_ATTR_SEC_W = 2,
+	TZC_ATTR_SEC_RW	 = 3
+};
+
+struct tzc_region {
+	uintptr_t base;
+	uintptr_t top;
+	enum tzc_sec_mode sec_mode;
+	uint16_t nsec_id;
+	uint16_t filters_mask;
+};
+
+int tzc_configure(uintptr_t tzc, const struct tzc_region *cfg);
+int tzc_disable_filters(uintptr_t tzc, uint16_t filters_mask);
+int tzc_enable_filters(uintptr_t tzc, uint16_t filters_mask);
+void tzc_dump_config(uintptr_t tzc);
+
+#endif /* MACH_TZC_H */
diff --git a/arch/arm/mach-stm32mp/tzc400.c b/arch/arm/mach-stm32mp/tzc400.c
new file mode 100644
index 0000000000..cdc4a40eda
--- /dev/null
+++ b/arch/arm/mach-stm32mp/tzc400.c
@@ -0,0 +1,136 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Simple API for configuring TrustZone memory restrictions for TZC400
+ */
+
+#define LOG_CATEGORY LOGC_ARCH
+
+#include <linux/iopoll.h>
+#include <mach/tzc.h>
+
+#define TZC_TIMEOUT_US		100
+
+#define TZC_BUILD_CONFIG	0x00
+#define TZC_ACTION		0x04
+#define TZC_ACTION_NONE		0
+#define TZC_ACTION_ERR		1
+#define TZC_ACTION_INT		2
+#define TZC_ACTION_INT_ERR	3
+#define TZC_GATE_KEEPER		0x08
+
+#define TZC_REGION0_OFFSET	0x100
+#define TZC_REGION_CFG_SIZE	0x20
+#define TZC_REGION1_OFFSET	0x120
+#define TZC_REGION_BASE		0x00
+#define TZC_REGION_TOP		0x08
+#define TZC_REGION_ATTRIBUTE	0x10
+#define TZC_REGION_ACCESS	0x14
+
+static uint32_t tzc_read(uintptr_t tzc, size_t reg)
+{
+	return readl(tzc + reg);
+}
+
+static void tzc_write(uintptr_t tzc, size_t reg, uint32_t val)
+{
+	writel(val, tzc + reg);
+}
+
+static uint16_t tzc_config_get_active_filters(const struct tzc_region *cfg)
+{
+	uint16_t active_filters = 0;
+
+	for ( ; cfg->top != 0; cfg++)
+		active_filters |= cfg->filters_mask;
+
+	return active_filters;
+}
+
+int tzc_configure(uintptr_t tzc, const struct tzc_region *cfg)
+{
+	uintptr_t region = tzc + TZC_REGION1_OFFSET;
+	uint32_t nsid, attr_reg, active_filters;
+	int ret;
+
+	active_filters = tzc_config_get_active_filters(cfg);
+	if (active_filters == 0)
+		return -EINVAL;
+
+	ret = tzc_disable_filters(tzc, active_filters);
+	if (ret < 0)
+		return ret;
+
+	for ( ; cfg->top != 0; cfg++, region += TZC_REGION_CFG_SIZE) {
+		attr_reg = (cfg->sec_mode & 0x03) << 30;
+		attr_reg |= (cfg->filters_mask & 0x03) << 0;
+		nsid = cfg->nsec_id & 0xffff;
+		nsid |= nsid << 16;
+
+		tzc_write(region, TZC_REGION_BASE, cfg->base);
+		tzc_write(region, TZC_REGION_TOP, cfg->top);
+		tzc_write(region, TZC_REGION_ACCESS, nsid);
+		tzc_write(region, TZC_REGION_ATTRIBUTE, attr_reg);
+	}
+
+	tzc_write(tzc, TZC_ACTION, TZC_ACTION_ERR);
+	return tzc_enable_filters(tzc, active_filters);
+}
+
+int tzc_disable_filters(uintptr_t tzc, uint16_t filters_mask)
+{
+	uint32_t gate = tzc_read(tzc, TZC_GATE_KEEPER);
+	uint32_t filter_status = filters_mask << 16;
+
+	gate &= ~filters_mask;
+	tzc_write(tzc, TZC_GATE_KEEPER, gate);
+
+	return readl_poll_timeout(tzc + TZC_GATE_KEEPER, gate,
+				 (gate & filter_status) == 0, TZC_TIMEOUT_US);
+}
+
+int tzc_enable_filters(uintptr_t tzc, uint16_t filters_mask)
+{
+	uint32_t gate = tzc_read(tzc, TZC_GATE_KEEPER);
+	uint32_t filter_status = filters_mask << 16;
+
+	gate |= filters_mask;
+	tzc_write(tzc, TZC_GATE_KEEPER, gate);
+
+	return readl_poll_timeout(tzc + TZC_GATE_KEEPER, gate,
+				 (gate & filter_status) == filter_status,
+				 TZC_TIMEOUT_US);
+}
+
+static const char *sec_access_str_from_attr(uint32_t attr)
+{
+	const char *const sec_mode[] = { "none", "RO  ", "WO  ", "RW  " };
+
+	return sec_mode[(attr >> 30) & 0x03];
+}
+
+void tzc_dump_config(uintptr_t tzc)
+{
+	uint32_t build_config, base, top, attr, nsaid;
+	int num_regions, i;
+	uintptr_t region;
+
+	build_config = tzc_read(tzc, TZC_BUILD_CONFIG);
+	num_regions = ((build_config >> 0) & 0x1f) + 1;
+
+	for (i = 0; i < num_regions; i++) {
+		region = tzc + TZC_REGION0_OFFSET + i * TZC_REGION_CFG_SIZE;
+
+		base = tzc_read(region, TZC_REGION_BASE);
+		top = tzc_read(region, TZC_REGION_TOP);
+		attr = tzc_read(region, TZC_REGION_ATTRIBUTE);
+		nsaid = tzc_read(region, TZC_REGION_ACCESS);
+
+		if (attr == 0 && nsaid == 0)
+			continue;
+
+		log_info("TZC region %u: %08x->%08x - filters 0x%x\n",
+			 i, base, top, (attr >> 0) & 0xf);
+		log_info("\t Secure access %s NSAID %08x\n",
+			 sec_access_str_from_attr(attr), nsaid);
+	}
+}