[PATCH v2 3/5] bus: add driver for IMX AIPSTZ bridge

[Laurentiu Mihalcea]

From: Laurentiu Mihalcea <laurentiu.mihalcea at nxp.com>

The secure AHB to IP Slave (AIPSTZ) bus bridge provides access control
configurations meant to restrict access to certain peripherals.
Some of the configurations include:

	1) Marking masters as trusted for R/W. Based on this
	(and the configuration of the accessed peripheral), the bridge
	may choose to abort the R/W transactions issued by certain
	masters.

	2) Allowing/disallowing write accesses to peripherals.

Add driver for this IP. Since there's currently no framework for
access controllers (and since there's currently no need for having
flexibility w.r.t the configurations) all this driver does is it
applies a relaxed, "default" configuration, in which all masters
are trusted for R/W.

Note that some instances of this IP (e.g: AIPSTZ5 on i.MX8MP) may be tied
to a power domain and may lose their configuration when the domain is
powered off. This is why the configuration has to be restored when the
domain is powered on.

Co-developed-by: Daniel Baluta <daniel.baluta at nxp.com>
Signed-off-by: Daniel Baluta <daniel.baluta at nxp.com>
Signed-off-by: Laurentiu Mihalcea <laurentiu.mihalcea at nxp.com>
---
 drivers/bus/Kconfig      |  6 +++
 drivers/bus/Makefile     |  1 +
 drivers/bus/imx-aipstz.c | 92 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 99 insertions(+)
 create mode 100644 drivers/bus/imx-aipstz.c

diff --git a/drivers/bus/Kconfig b/drivers/bus/Kconfig
index ff669a8ccad9..fe7600283e70 100644
--- a/drivers/bus/Kconfig
+++ b/drivers/bus/Kconfig
@@ -87,6 +87,12 @@ config HISILICON_LPC
 	  Driver to enable I/O access to devices attached to the Low Pin
 	  Count bus on the HiSilicon Hip06/7 SoC.
 
+config IMX_AIPSTZ
+	tristate "Support for IMX Secure AHB to IP Slave bus (AIPSTZ) bridge"
+	depends on ARCH_MXC
+	help
+	  Enable support for IMX AIPSTZ bridge.
+
 config IMX_WEIM
 	bool "Freescale EIM DRIVER"
 	depends on ARCH_MXC || COMPILE_TEST
diff --git a/drivers/bus/Makefile b/drivers/bus/Makefile
index cddd4984d6af..8e693fe8a03a 100644
--- a/drivers/bus/Makefile
+++ b/drivers/bus/Makefile
@@ -15,6 +15,7 @@ obj-$(CONFIG_FSL_MC_BUS)	+= fsl-mc/
 
 obj-$(CONFIG_BT1_APB)		+= bt1-apb.o
 obj-$(CONFIG_BT1_AXI)		+= bt1-axi.o
+obj-$(CONFIG_IMX_AIPSTZ)	+= imx-aipstz.o
 obj-$(CONFIG_IMX_WEIM)		+= imx-weim.o
 obj-$(CONFIG_INTEL_IXP4XX_EB)	+= intel-ixp4xx-eb.o
 obj-$(CONFIG_MIPS_CDMM)		+= mips_cdmm.o
diff --git a/drivers/bus/imx-aipstz.c b/drivers/bus/imx-aipstz.c
new file mode 100644
index 000000000000..c90580da17a1
--- /dev/null
+++ b/drivers/bus/imx-aipstz.c
@@ -0,0 +1,92 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2025 NXP
+ */
+
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
+#include <linux/regmap.h>
+
+#define IMX_AIPSTZ_MPR0 0x0
+
+struct imx_aipstz_config {
+	u32 mpr0;
+};
+
+static void imx_aipstz_apply_default(void __iomem *base,
+				     const struct imx_aipstz_config *default_cfg)
+{
+	writel(default_cfg->mpr0, base + IMX_AIPSTZ_MPR0);
+}
+
+static int imx_aipstz_probe(struct platform_device *pdev)
+{
+	const struct imx_aipstz_config *default_cfg;
+	void __iomem *base;
+
+	base = devm_platform_get_and_ioremap_resource(pdev, 0, NULL);
+	if (IS_ERR(base))
+		return dev_err_probe(&pdev->dev, -ENOMEM,
+				     "failed to get/ioremap memory\n");
+
+	default_cfg = of_device_get_match_data(&pdev->dev);
+
+	imx_aipstz_apply_default(base, default_cfg);
+
+	dev_set_drvdata(&pdev->dev, base);
+
+	pm_runtime_set_active(&pdev->dev);
+	devm_pm_runtime_enable(&pdev->dev);
+
+	return devm_of_platform_populate(&pdev->dev);
+}
+
+static int imx_aipstz_runtime_resume(struct device *dev)
+{
+	const struct imx_aipstz_config *default_cfg;
+	void __iomem *base;
+
+	base = dev_get_drvdata(dev);
+	default_cfg = of_device_get_match_data(dev);
+
+	/* restore potentially lost configuration during domain power-off */
+	imx_aipstz_apply_default(base, default_cfg);
+
+	return 0;
+}
+
+static const struct dev_pm_ops imx_aipstz_pm_ops = {
+	RUNTIME_PM_OPS(NULL, imx_aipstz_runtime_resume, NULL)
+	SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend, pm_runtime_force_resume)
+};
+
+/*
+ * following configuration is equivalent to:
+ *	masters 0-7 => trusted for R/W + use AHB's HPROT[1] to det. privilege
+ */
+static const struct imx_aipstz_config imx8mp_aipstz_default_cfg = {
+	.mpr0 = 0x77777777,
+};
+
+static const struct of_device_id imx_aipstz_of_ids[] = {
+	{ .compatible = "fsl,imx8mp-aipstz", .data = &imx8mp_aipstz_default_cfg },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, imx_aipstz_of_ids);
+
+static struct platform_driver imx_aipstz_of_driver = {
+	.probe = imx_aipstz_probe,
+	.driver = {
+		.name = "imx-aipstz",
+		.of_match_table = imx_aipstz_of_ids,
+		.pm = pm_ptr(&imx_aipstz_pm_ops),
+	},
+};
+module_platform_driver(imx_aipstz_of_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("IMX secure AHB to IP Slave bus (AIPSTZ) bridge driver");
+MODULE_AUTHOR("Laurentiu Mihalcea <laurentiu.mihalcea at nxp.com>");
-- 
2.34.1