bus: rifsc: introduce RIFSC firewall controller driver

RIFSC is a peripheral firewall controller that filter accesses based on
Arm TrustZone secure state, Arm CPU privilege execution level and
Compartment IDentification of the STM32 SoC subsystems.

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

MAINTAINERS

@@ -20815,6 +20815,7 @@ ST STM32 FIREWALL
 M:	Gatien Chevallier <gatien.chevallier@foss.st.com>
 S:	Maintained
 F:	drivers/bus/stm32_firewall.c
+F:	drivers/bus/stm32_rifsc.c
 
 ST STM32 I2C/SMBUS DRIVER
 M:	Pierre-Yves MORDRET <pierre-yves.mordret@foss.st.com>

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-$(CONFIG_STM32_FIREWALL)	+= stm32_firewall.o
+obj-$(CONFIG_STM32_FIREWALL)	+= stm32_firewall.o stm32_rifsc.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_rifsc.c

@@ -0,0 +1,252 @@
+// 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"
+
+/*
+ * RIFSC offset register
+ */
+#define RIFSC_RISC_SECCFGR0		0x10
+#define RIFSC_RISC_PRIVCFGR0		0x30
+#define RIFSC_RISC_PER0_CIDCFGR		0x100
+#define RIFSC_RISC_PER0_SEMCR		0x104
+#define RIFSC_RISC_HWCFGR2		0xFEC
+
+/*
+ * SEMCR register
+ */
+#define SEMCR_MUTEX			BIT(0)
+
+/*
+ * HWCFGR2 register
+ */
+#define HWCFGR2_CONF1_MASK		GENMASK(15, 0)
+#define HWCFGR2_CONF2_MASK		GENMASK(23, 16)
+#define HWCFGR2_CONF3_MASK		GENMASK(31, 24)
+
+/*
+ * RIFSC miscellaneous
+ */
+#define RIFSC_RISC_CFEN_MASK		BIT(0)
+#define RIFSC_RISC_SEM_EN_MASK		BIT(1)
+#define RIFSC_RISC_SCID_MASK		GENMASK(6, 4)
+#define RIFSC_RISC_SEML_SHIFT		16
+#define RIFSC_RISC_SEMWL_MASK		GENMASK(23, 16)
+#define RIFSC_RISC_PER_ID_MASK		GENMASK(31, 24)
+
+#define RIFSC_RISC_PERx_CID_MASK	(RIFSC_RISC_CFEN_MASK | \
+					 RIFSC_RISC_SEM_EN_MASK | \
+					 RIFSC_RISC_SCID_MASK | \
+					 RIFSC_RISC_SEMWL_MASK)
+
+#define IDS_PER_RISC_SEC_PRIV_REGS	32
+
+/* RIF miscellaneous */
+/*
+ * CIDCFGR register fields
+ */
+#define CIDCFGR_CFEN			BIT(0)
+#define CIDCFGR_SEMEN			BIT(1)
+#define CIDCFGR_SEMWL(x)		BIT(RIFSC_RISC_SEML_SHIFT + (x))
+
+#define SEMWL_SHIFT			16
+
+/* Compartiment IDs */
+#define RIF_CID0			0x0
+#define RIF_CID1			0x1
+
+static bool stm32_rifsc_is_semaphore_available(void __iomem *addr)
+{
+	return !(readl(addr) & SEMCR_MUTEX);
+}
+
+static int stm32_rif_acquire_semaphore(struct stm32_firewall_controller *stm32_firewall_controller,
+				       int id)
+{
+	void __iomem *addr = stm32_firewall_controller->mmio + RIFSC_RISC_PER0_SEMCR + 0x8 * id;
+
+	writel(SEMCR_MUTEX, addr);
+
+	/* Check that CID1 has the semaphore */
+	if (stm32_rifsc_is_semaphore_available(addr) ||
+	    FIELD_GET(RIFSC_RISC_SCID_MASK, readl(addr)) != RIF_CID1)
+		return -EACCES;
+
+	return 0;
+}
+
+static void stm32_rif_release_semaphore(struct stm32_firewall_controller *stm32_firewall_controller,
+					int id)
+{
+	void __iomem *addr = stm32_firewall_controller->mmio + RIFSC_RISC_PER0_SEMCR + 0x8 * id;
+
+	if (stm32_rifsc_is_semaphore_available(addr))
+		return;
+
+	writel(SEMCR_MUTEX, addr);
+
+	/* Ok if another compartment takes the semaphore before the check */
+	WARN_ON(!stm32_rifsc_is_semaphore_available(addr) &&
+		FIELD_GET(RIFSC_RISC_SCID_MASK, readl(addr)) == RIF_CID1);
+}
+
+static int stm32_rifsc_grant_access(struct stm32_firewall_controller *ctrl, u32 firewall_id)
+{
+	struct stm32_firewall_controller *rifsc_controller = ctrl;
+	u32 reg_offset, reg_id, sec_reg_value, cid_reg_value;
+	int rc;
+
+	if (firewall_id >= rifsc_controller->max_entries) {
+		dev_err(rifsc_controller->dev, "Invalid sys bus ID %u", firewall_id);
+		return -EINVAL;
+	}
+
+	/*
+	 * RIFSC_RISC_PRIVCFGRx and RIFSC_RISC_SECCFGRx both handle configuration access for
+	 * 32 peripherals. On the other hand, there is one _RIFSC_RISC_PERx_CIDCFGR register
+	 * per peripheral
+	 */
+	reg_id = firewall_id / IDS_PER_RISC_SEC_PRIV_REGS;
+	reg_offset = firewall_id % IDS_PER_RISC_SEC_PRIV_REGS;
+	sec_reg_value = readl(rifsc_controller->mmio + RIFSC_RISC_SECCFGR0 + 0x4 * reg_id);
+	cid_reg_value = readl(rifsc_controller->mmio + RIFSC_RISC_PER0_CIDCFGR + 0x8 * firewall_id);
+
+	/* First check conditions for semaphore mode, which doesn't take into account static CID. */
+	if ((cid_reg_value & CIDCFGR_SEMEN) && (cid_reg_value & CIDCFGR_CFEN)) {
+		if (cid_reg_value & BIT(RIF_CID1 + SEMWL_SHIFT)) {
+			/* Static CID is irrelevant if semaphore mode */
+			goto skip_cid_check;
+		} else {
+			dev_dbg(rifsc_controller->dev,
+				"Invalid bus semaphore configuration: index %d\n", firewall_id);
+			return -EACCES;
+		}
+	}
+
+	/*
+	 * Skip CID check if CID filtering isn't enabled or filtering is enabled on CID0, which
+	 * corresponds to whatever CID.
+	 */
+	if (!(cid_reg_value & CIDCFGR_CFEN) ||
+	    FIELD_GET(RIFSC_RISC_SCID_MASK, cid_reg_value) == RIF_CID0)
+		goto skip_cid_check;
+
+	/* Coherency check with the CID configuration */
+	if (FIELD_GET(RIFSC_RISC_SCID_MASK, cid_reg_value) != RIF_CID1) {
+		dev_dbg(rifsc_controller->dev, "Invalid CID configuration for peripheral: %d\n",
+			firewall_id);
+		return -EACCES;
+	}
+
+skip_cid_check:
+	/* Check security configuration */
+	if (sec_reg_value & BIT(reg_offset)) {
+		dev_dbg(rifsc_controller->dev,
+			"Invalid security configuration for peripheral: %d\n", firewall_id);
+		return -EACCES;
+	}
+
+	/*
+	 * If the peripheral is in semaphore mode, take the semaphore so that
+	 * the CID1 has the ownership.
+	 */
+	if ((cid_reg_value & CIDCFGR_SEMEN) && (cid_reg_value & CIDCFGR_CFEN)) {
+		rc = stm32_rif_acquire_semaphore(rifsc_controller, firewall_id);
+		if (rc) {
+			dev_err(rifsc_controller->dev,
+				"Couldn't acquire semaphore for peripheral: %d\n", firewall_id);
+			return rc;
+		}
+	}
+
+	return 0;
+}
+
+static void stm32_rifsc_release_access(struct stm32_firewall_controller *ctrl, u32 firewall_id)
+{
+	stm32_rif_release_semaphore(ctrl, firewall_id);
+}
+
+static int stm32_rifsc_probe(struct platform_device *pdev)
+{
+	struct stm32_firewall_controller *rifsc_controller;
+	struct device_node *np = pdev->dev.of_node;
+	u32 nb_risup, nb_rimu, nb_risal;
+	struct resource *res;
+	void __iomem *mmio;
+	int rc;
+
+	rifsc_controller = devm_kzalloc(&pdev->dev, sizeof(*rifsc_controller), GFP_KERNEL);
+	if (!rifsc_controller)
+		return -ENOMEM;
+
+	mmio = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
+	if (IS_ERR(mmio))
+		return PTR_ERR(mmio);
+
+	rifsc_controller->dev = &pdev->dev;
+	rifsc_controller->mmio = mmio;
+	rifsc_controller->name = dev_driver_string(rifsc_controller->dev);
+	rifsc_controller->type = STM32_PERIPHERAL_FIREWALL | STM32_MEMORY_FIREWALL;
+	rifsc_controller->grant_access = stm32_rifsc_grant_access;
+	rifsc_controller->release_access = stm32_rifsc_release_access;
+
+	/* Get number of RIFSC entries*/
+	nb_risup = readl(rifsc_controller->mmio + RIFSC_RISC_HWCFGR2) & HWCFGR2_CONF1_MASK;
+	nb_rimu = readl(rifsc_controller->mmio + RIFSC_RISC_HWCFGR2) & HWCFGR2_CONF2_MASK;
+	nb_risal = readl(rifsc_controller->mmio + RIFSC_RISC_HWCFGR2) & HWCFGR2_CONF3_MASK;
+	rifsc_controller->max_entries = nb_risup + nb_rimu + nb_risal;
+
+	platform_set_drvdata(pdev, rifsc_controller);
+
+	rc = stm32_firewall_controller_register(rifsc_controller);
+	if (rc) {
+		dev_err(rifsc_controller->dev, "Couldn't register as a firewall controller: %d",
+			rc);
+		return rc;
+	}
+
+	rc = stm32_firewall_populate_bus(rifsc_controller);
+	if (rc) {
+		dev_err(rifsc_controller->dev, "Couldn't populate RIFSC 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_rifsc_of_match[] = {
+	{ .compatible = "st,stm32mp25-rifsc" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, stm32_rifsc_of_match);
+
+static struct platform_driver stm32_rifsc_driver = {
+	.probe  = stm32_rifsc_probe,
+	.driver = {
+		.name = "stm32-rifsc",
+		.of_match_table = stm32_rifsc_of_match,
+	},
+};
+module_platform_driver(stm32_rifsc_driver);
+
+MODULE_AUTHOR("Gatien Chevallier <gatien.chevallier@foss.st.com>");
+MODULE_DESCRIPTION("STMicroelectronics RIFSC driver");
+MODULE_LICENSE("GPL");