bus: etzpc: introduce ETZPC firewall controller driver

ETZPC is a peripheral and memory firewall controller that filter accesses
based on Arm TrustZone secure state and Arm CPU privilege execution level.
It handles MCU isolation as well.

Signed-off-by: Gatien Chevallier <gatien.chevallier@foss.st.com>
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>

MAINTAINERS

@@ -20814,6 +20814,7 @@ F:	drivers/media/i2c/st-mipid02.c
 ST STM32 FIREWALL
 M:	Gatien Chevallier <gatien.chevallier@foss.st.com>
 S:	Maintained
+F:	drivers/bus/stm32_etzpc.c
 F:	drivers/bus/stm32_firewall.c
 F:	drivers/bus/stm32_rifsc.c
 

drivers/bus/Makefile

@@ -26,7 +26,7 @@ obj-$(CONFIG_OMAP_INTERCONNECT)	+= omap_l3_smx.o omap_l3_noc.o
 obj-$(CONFIG_OMAP_OCP2SCP)	+= omap-ocp2scp.o
 obj-$(CONFIG_QCOM_EBI2)		+= qcom-ebi2.o
 obj-$(CONFIG_QCOM_SSC_BLOCK_BUS)	+= qcom-ssc-block-bus.o
-obj-$(CONFIG_STM32_FIREWALL)	+= stm32_firewall.o stm32_rifsc.o
+obj-$(CONFIG_STM32_FIREWALL)	+= stm32_firewall.o stm32_rifsc.o stm32_etzpc.o
 obj-$(CONFIG_SUN50I_DE2_BUS)	+= sun50i-de2.o
 obj-$(CONFIG_SUNXI_RSB)		+= sunxi-rsb.o
 obj-$(CONFIG_OF)		+= simple-pm-bus.o

drivers/bus/stm32_etzpc.c

@@ -0,0 +1,141 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2023, STMicroelectronics - All Rights Reserved
+ */
+
+#include <linux/bitfield.h>
+#include <linux/bits.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/types.h>
+
+#include "stm32_firewall.h"
+
+/*
+ * ETZPC registers
+ */
+#define ETZPC_DECPROT			0x10
+#define ETZPC_HWCFGR			0x3F0
+
+/*
+ * HWCFGR register
+ */
+#define ETZPC_HWCFGR_NUM_TZMA		GENMASK(7, 0)
+#define ETZPC_HWCFGR_NUM_PER_SEC	GENMASK(15, 8)
+#define ETZPC_HWCFGR_NUM_AHB_SEC	GENMASK(23, 16)
+#define ETZPC_HWCFGR_CHUNKS1N4		GENMASK(31, 24)
+
+/*
+ * ETZPC miscellaneous
+ */
+#define ETZPC_PROT_MASK			GENMASK(1, 0)
+#define ETZPC_PROT_A7NS			0x3
+#define ETZPC_DECPROT_SHIFT		1
+
+#define IDS_PER_DECPROT_REGS		16
+
+static int stm32_etzpc_grant_access(struct stm32_firewall_controller *ctrl, u32 firewall_id)
+{
+	u32 offset, reg_offset, sec_val;
+
+	if (firewall_id >= ctrl->max_entries) {
+		dev_err(ctrl->dev, "Invalid sys bus ID %u", firewall_id);
+		return -EINVAL;
+	}
+
+	/* Check access configuration, 16 peripherals per register */
+	reg_offset = ETZPC_DECPROT + 0x4 * (firewall_id / IDS_PER_DECPROT_REGS);
+	offset = (firewall_id % IDS_PER_DECPROT_REGS) << ETZPC_DECPROT_SHIFT;
+
+	/* Verify peripheral is non-secure and attributed to cortex A7 */
+	sec_val = (readl(ctrl->mmio + reg_offset) >> offset) & ETZPC_PROT_MASK;
+	if (sec_val != ETZPC_PROT_A7NS) {
+		dev_dbg(ctrl->dev, "Invalid bus configuration: reg_offset %#x, value %d\n",
+			reg_offset, sec_val);
+		return -EACCES;
+	}
+
+	return 0;
+}
+
+static void stm32_etzpc_release_access(struct stm32_firewall_controller *ctrl __maybe_unused,
+				       u32 firewall_id __maybe_unused)
+{
+}
+
+static int stm32_etzpc_probe(struct platform_device *pdev)
+{
+	struct stm32_firewall_controller *etzpc_controller;
+	struct device_node *np = pdev->dev.of_node;
+	u32 nb_per, nb_master;
+	struct resource *res;
+	void __iomem *mmio;
+	int rc;
+
+	etzpc_controller = devm_kzalloc(&pdev->dev, sizeof(*etzpc_controller), GFP_KERNEL);
+	if (!etzpc_controller)
+		return -ENOMEM;
+
+	mmio = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
+	if (IS_ERR(mmio))
+		return PTR_ERR(mmio);
+
+	etzpc_controller->dev = &pdev->dev;
+	etzpc_controller->mmio = mmio;
+	etzpc_controller->name = dev_driver_string(etzpc_controller->dev);
+	etzpc_controller->type = STM32_PERIPHERAL_FIREWALL | STM32_MEMORY_FIREWALL;
+	etzpc_controller->grant_access = stm32_etzpc_grant_access;
+	etzpc_controller->release_access = stm32_etzpc_release_access;
+
+	/* Get number of etzpc entries*/
+	nb_per = FIELD_GET(ETZPC_HWCFGR_NUM_PER_SEC,
+			   readl(etzpc_controller->mmio + ETZPC_HWCFGR));
+	nb_master = FIELD_GET(ETZPC_HWCFGR_NUM_AHB_SEC,
+			      readl(etzpc_controller->mmio + ETZPC_HWCFGR));
+	etzpc_controller->max_entries = nb_per + nb_master;
+
+	platform_set_drvdata(pdev, etzpc_controller);
+
+	rc = stm32_firewall_controller_register(etzpc_controller);
+	if (rc) {
+		dev_err(etzpc_controller->dev, "Couldn't register as a firewall controller: %d",
+			rc);
+		return rc;
+	}
+
+	rc = stm32_firewall_populate_bus(etzpc_controller);
+	if (rc) {
+		dev_err(etzpc_controller->dev, "Couldn't populate ETZPC bus: %d",
+			rc);
+		return rc;
+	}
+
+	/* Populate all allowed nodes */
+	return of_platform_populate(np, NULL, NULL, &pdev->dev);
+}
+
+static const struct of_device_id stm32_etzpc_of_match[] = {
+	{ .compatible = "st,stm32-etzpc" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, stm32_etzpc_of_match);
+
+static struct platform_driver stm32_etzpc_driver = {
+	.probe  = stm32_etzpc_probe,
+	.driver = {
+		.name = "stm32-etzpc",
+		.of_match_table = stm32_etzpc_of_match,
+	},
+};
+module_platform_driver(stm32_etzpc_driver);
+
+MODULE_AUTHOR("Gatien Chevallier <gatien.chevallier@foss.st.com>");
+MODULE_DESCRIPTION("STMicroelectronics ETZPC driver");
+MODULE_LICENSE("GPL");