mailbox: arm_mhuv2: Add driver

This adds driver for the ARM MHUv2 (Message Handling Unit) mailbox
controller.

This is based on the accepted DT bindings of the controller and supports
combination of both transport protocols, i.e. doorbell and data-transfer.

Transmitting and receiving data through the mailbox framework is done
through struct arm_mhuv2_mbox_msg.

Based on the initial work done by Morten Borup Petersen from ARM.
Co-developed-by: Tushar Khandelwal <tushar.khandelwal@arm.com>
Signed-off-by: Tushar Khandelwal <tushar.khandelwal@arm.com>
Tested-by: Usama Arif <usama.arif@arm.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>

MAINTAINERS

@@ -10418,6 +10418,15 @@ F:	drivers/mailbox/
 F:	include/linux/mailbox_client.h
 F:	include/linux/mailbox_controller.h
 
+MAILBOX ARM MHUv2
+M:	Viresh Kumar <viresh.kumar@linaro.org>
+M:	Tushar Khandelwal <Tushar.Khandelwal@arm.com>
+L:	linux-kernel@vger.kernel.org
+S:	Maintained
+F:	drivers/mailbox/arm_mhuv2.c
+F:	include/linux/mailbox/arm_mhuv2_message.h
+F:	Documentation/devicetree/bindings/mailbox/arm,mhuv2.yaml
+
 MAN-PAGES: MANUAL PAGES FOR LINUX -- Sections 2, 3, 4, 5, and 7
 M:	Michael Kerrisk <mtk.manpages@gmail.com>
 L:	linux-man@vger.kernel.org

drivers/mailbox/Kconfig

@@ -16,6 +16,13 @@ config ARM_MHU
 	  The controller has 3 mailbox channels, the last of which can be
 	  used in Secure mode only.
 
+config ARM_MHU_V2
+	tristate "ARM MHUv2 Mailbox"
+	depends on ARM_AMBA
+	help
+	  Say Y here if you want to build the ARM MHUv2 controller driver,
+	  which provides unidirectional mailboxes between processing elements.
+
 config IMX_MBOX
 	tristate "i.MX Mailbox"
 	depends on ARCH_MXC || COMPILE_TEST

drivers/mailbox/Makefile

@@ -7,6 +7,8 @@ obj-$(CONFIG_MAILBOX_TEST)	+= mailbox-test.o
 
 obj-$(CONFIG_ARM_MHU)	+= arm_mhu.o arm_mhu_db.o
 
+obj-$(CONFIG_ARM_MHU_V2)	+= arm_mhuv2.o
+
 obj-$(CONFIG_IMX_MBOX)	+= imx-mailbox.o
 
 obj-$(CONFIG_ARMADA_37XX_RWTM_MBOX)	+= armada-37xx-rwtm-mailbox.o

include/linux/mailbox/arm_mhuv2_message.h

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * ARM MHUv2 Mailbox Message
+ *
+ * Copyright (C) 2020 Arm Ltd.
+ * Copyright (C) 2020 Linaro Ltd.
+ */
+
+#ifndef _LINUX_ARM_MHUV2_MESSAGE_H_
+#define _LINUX_ARM_MHUV2_MESSAGE_H_
+
+#include <linux/types.h>
+
+/* Data structure for data-transfer protocol */
+struct arm_mhuv2_mbox_msg {
+	void *data;
+	size_t len;
+};
+
+#endif /* _LINUX_ARM_MHUV2_MESSAGE_H_ */