mailbox: add Microchip IPC support

Add a mailbox controller driver for the Microchip Inter-processor
Communication (IPC), which is used to send and receive data between
processors.

The driver uses the RISC-V Supervisor Binary Interface (SBI) to
communicate with software running in machine mode (M-mode) to access
the IPC hardware block.

Additional details on the Microchip vendor extension and the IPC
function IDs described in the driver can be found in the following
documentation:

https://github.com/linux4microchip/microchip-sbi-ecall-extension

This SBI interface in this driver is compatible with the Mi-V Inter-hart
Communication (IHC) IP.

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

Signed-off-by: Valentina Fernandez <valentina.fernandezalanis@microchip.com>
Signed-off-by: Jassi Brar <jassisinghbrar@gmail.com>

drivers/mailbox/Kconfig

@@ -178,6 +178,19 @@ config POLARFIRE_SOC_MAILBOX
 
 	  If unsure, say N.
 
+config MCHP_SBI_IPC_MBOX
+	tristate "Microchip Inter-processor Communication (IPC) SBI driver"
+	depends on RISCV_SBI || COMPILE_TEST
+	depends on ARCH_MICROCHIP
+	help
+	  Mailbox implementation for Microchip devices with an
+	  Inter-process communication (IPC) controller.
+
+	  To compile this driver as a module, choose M here. the
+	  module will be called mailbox-mchp-ipc-sbi.
+
+	  If unsure, say N.
+
 config QCOM_APCS_IPC
 	tristate "Qualcomm APCS IPC driver"
 	depends on ARCH_QCOM || COMPILE_TEST

drivers/mailbox/Makefile

@@ -45,6 +45,8 @@ obj-$(CONFIG_BCM_FLEXRM_MBOX)	+= bcm-flexrm-mailbox.o
 
 obj-$(CONFIG_POLARFIRE_SOC_MAILBOX)	+= mailbox-mpfs.o
 
+obj-$(CONFIG_MCHP_SBI_IPC_MBOX)		+= mailbox-mchp-ipc-sbi.o
+
 obj-$(CONFIG_QCOM_APCS_IPC)	+= qcom-apcs-ipc-mailbox.o
 
 obj-$(CONFIG_TEGRA_HSP_MBOX)	+= tegra-hsp.o

include/linux/mailbox/mchp-ipc.h

@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ *Copyright (c) 2024 Microchip Technology Inc. All rights reserved.
+ */
+
+#ifndef _LINUX_MCHP_IPC_H_
+#define _LINUX_MCHP_IPC_H_
+
+#include <linux/mailbox_controller.h>
+#include <linux/types.h>
+
+struct mchp_ipc_msg {
+	u32 *buf;
+	u16 size;
+};
+
+struct mchp_ipc_sbi_chan {
+	void *buf_base_tx;
+	void *buf_base_rx;
+	void *msg_buf_tx;
+	void *msg_buf_rx;
+	phys_addr_t buf_base_tx_addr;
+	phys_addr_t buf_base_rx_addr;
+	phys_addr_t msg_buf_tx_addr;
+	phys_addr_t msg_buf_rx_addr;
+	int chan_aggregated_irq;
+	int mp_irq;
+	int mc_irq;
+	u32 id;
+	u32 max_msg_size;
+};
+
+#endif /* _LINUX_MCHP_IPC_H_ */