The goal of these helpers are to offer an interface for the
hardware blocks controlling bus accesses rights.

Bus firewall controllers are typically used to control if a
hardware block can perform read or write operations on bus.

Smarter firewall controllers could be able to define accesses
rights per hardware blocks to control where they can read
or write.

Firewall controller configurations are provided in device node,
parsed by the helpers and send to the driver to apply them.
Each controller may need different number and type of inputs
to configure the firewall so device-tree properties size have to
be define by using "#firewall-cells".
Firewall configurations properties have to be named "firewall-X"
on device node.
"firewall-names" keyword can also be used to give a name to
a specific configuration.

Example of device-tree:
ctrl0: firewall@0 {
	#firewall-cells = <2>;
      };

foo: foo@0 {
	firewall-names = "default", "setting1";
	firewall-0 = <&ctrl0 1 2>;
	firewall-1 = <&ctrl0 3 4>;
};

Configurations could be applied with functions like
firewall_set_config_by_index() or firewall_set_config_by_name().

firewall_set_default_config() function will apply the
configuration named "default" (if existing) or the configuration
with index 0 (i.e. firewall-0).

Drivers could register/unregister themselves be calling
firewall_register/firewall_unregister functions.

Signed-off-by: Benjamin Gaignard <redacted>
---
 drivers/bus/Kconfig          |   2 +
 drivers/bus/Makefile         |   2 +
 drivers/bus/stm32/Kconfig    |   3 +
 drivers/bus/stm32/Makefile   |   1 +
 drivers/bus/stm32/firewall.c | 266 +++++++++++++++++++++++++++++++++++++++++++
 drivers/bus/stm32/firewall.h |  75 ++++++++++++
 6 files changed, 349 insertions(+)
 create mode 100644 drivers/bus/stm32/Kconfig
 create mode 100644 drivers/bus/stm32/Makefile
 create mode 100644 drivers/bus/stm32/firewall.c
 create mode 100644 drivers/bus/stm32/firewall.h

diff --git a/drivers/bus/Kconfig b/drivers/bus/Kconfig
index 6d4e4497b59b..843b356322d9 100644
--- a/drivers/bus/Kconfig
+++ b/drivers/bus/Kconfig

@@ -203,4 +203,6 @@ config DA8XX_MSTPRI
 source "drivers/bus/fsl-mc/Kconfig"
 source "drivers/bus/mhi/Kconfig"
 
+source "drivers/bus/stm32/Kconfig"
+
 endmenu

diff --git a/drivers/bus/Makefile b/drivers/bus/Makefile
index 05f32cd694a4..5e0e34b10235 100644
--- a/drivers/bus/Makefile
+++ b/drivers/bus/Makefile

@@ -37,3 +37,5 @@ obj-$(CONFIG_DA8XX_MSTPRI)	+= da8xx-mstpri.o
 
 # MHI
 obj-$(CONFIG_MHI_BUS)		+= mhi/
+
+obj-$(CONFIG_MACH_STM32MP157) 	+= stm32/

\ No newline at end of file

diff --git a/drivers/bus/stm32/Kconfig b/drivers/bus/stm32/Kconfig
new file mode 100644
index 000000000000..57221e833e2d
--- /dev/null
+++ b/drivers/bus/stm32/Kconfig

@@ -0,0 +1,3 @@
+config FIREWALL_CONTROLLERS
+	bool "Support of bus firewall controllers"
+	depends on OF

diff --git a/drivers/bus/stm32/Makefile b/drivers/bus/stm32/Makefile
new file mode 100644
index 000000000000..eb6b978d6450
--- /dev/null
+++ b/drivers/bus/stm32/Makefile

@@ -0,0 +1 @@
+obj-$(CONFIG_FIREWALL_CONTROLLERS) += firewall.o

diff --git a/drivers/bus/stm32/firewall.c b/drivers/bus/stm32/firewall.c
new file mode 100644
index 000000000000..95f716cf926f
--- /dev/null
+++ b/drivers/bus/stm32/firewall.c

@@ -0,0 +1,266 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) STMicroelectronics 2020 - All Rights Reserved
+ * Author: Benjamin Gaignard <benjamin.gaignard@st.com> for STMicroelectronics.
+ */
+
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/of.h>
+#include <linux/slab.h>
+
+#include "firewall.h"
+
+/* Mutex taken to protect firewall_list */
+static DEFINE_MUTEX(firewall_list_mutex);
+
+/* Global list of firewall control devices */
+static LIST_HEAD(firewall_list);