[PATCH 6/9] accel/neutron: Add mailbox support

[Ioana Ciocoi-Radulescu]

The driver communicates with the Neutron firmware via eight
register-backed mailboxes. A subset of the mailbox registers are
used to pass commands from driver to Neutron, while the rest are
written by Neutron firmware with status/ack info.

Signed-off-by: Jiwei Fu <jiwei.fu at nxp.com>
Signed-off-by: Ioana Ciocoi-Radulescu <ruxandra.radulescu at nxp.com>
---
 drivers/accel/neutron/Makefile          |  3 ++-
 drivers/accel/neutron/neutron_device.c  |  4 +++
 drivers/accel/neutron/neutron_mailbox.c | 47 +++++++++++++++++++++++++++++++++
 drivers/accel/neutron/neutron_mailbox.h | 42 +++++++++++++++++++++++++++++
 4 files changed, 95 insertions(+), 1 deletion(-)

diff --git a/drivers/accel/neutron/Makefile b/drivers/accel/neutron/Makefile
index d4298c7a8535..192ed896a9f9 100644
--- a/drivers/accel/neutron/Makefile
+++ b/drivers/accel/neutron/Makefile
@@ -5,4 +5,5 @@ obj-$(CONFIG_DRM_ACCEL_NXP_NEUTRON) := neutron.o
 neutron-y := \
 	neutron_driver.o \
 	neutron_device.o \
-	neutron_gem.o
+	neutron_gem.o \
+	neutron_mailbox.o
diff --git a/drivers/accel/neutron/neutron_device.c b/drivers/accel/neutron/neutron_device.c
index 61b3c96b4996..e5c09105be99 100644
--- a/drivers/accel/neutron/neutron_device.c
+++ b/drivers/accel/neutron/neutron_device.c
@@ -7,6 +7,7 @@
 #include <linux/iopoll.h>
 
 #include "neutron_device.h"
+#include "neutron_mailbox.h"
 
 void neutron_enable_irq(struct neutron_device *ndev)
 {
@@ -148,6 +149,9 @@ int neutron_boot(struct neutron_device *ndev)
 	if (ret)
 		return ret;
 
+	/* Prepare device to receive jobs */
+	neutron_mbox_reset_state(ndev);
+
 	ndev->flags |= NEUTRON_BOOTED;
 
 	return 0;
diff --git a/drivers/accel/neutron/neutron_mailbox.c b/drivers/accel/neutron/neutron_mailbox.c
new file mode 100644
index 000000000000..327ef2e8081d
--- /dev/null
+++ b/drivers/accel/neutron/neutron_mailbox.c
@@ -0,0 +1,47 @@
+// SPDX-License-Identifier: GPL-2.0+
+/* Copyright 2023, 2025-2026 NXP */
+
+#include <linux/iopoll.h>
+
+#include "neutron_device.h"
+#include "neutron_mailbox.h"
+
+#define NEUTRON_MBOX_FW_STATUS(dev)	NEUTRON_REG(dev, MBOX0)
+#define NEUTRON_MBOX_FW_ERRCODE(dev)	NEUTRON_REG(dev, MBOX1)
+#define NEUTRON_MBOX_CMD_ID(dev)	NEUTRON_REG(dev, MBOX3)
+#define NEUTRON_MBOX_CMD_ARG_BASE(dev)	NEUTRON_REG(dev, MBOX4)
+#define NEUTRON_MBOX_CMD_ARG(dev, i)	(NEUTRON_MBOX_CMD_ARG_BASE(dev) + (i) * 4)
+
+int neutron_mbox_send_cmd(struct neutron_device *ndev, struct neutron_mbox_cmd *cmd)
+{
+	u32 status;
+	int i;
+
+	/* Make sure Neutron is ready to receive commands */
+	status = readl_relaxed(NEUTRON_MBOX_FW_STATUS(ndev));
+	if (status != NEUTRON_FW_STATUS_RESET)
+		return -EBUSY;
+
+	for (i = 0; i < NEUTRON_MBOX_MAX_CMD_ARGS; i++)
+		writel_relaxed(cmd->args[i], NEUTRON_MBOX_CMD_ARG(ndev, i));
+	writel(cmd->id, NEUTRON_MBOX_CMD_ID(ndev));
+
+	return 0;
+}
+
+int neutron_mbox_reset_state(struct neutron_device *ndev)
+{
+	u32 status;
+
+	writel_relaxed(NEUTRON_CMD_RESET_STATE, NEUTRON_MBOX_CMD_ID(ndev));
+
+	return readl_poll_timeout(NEUTRON_MBOX_FW_STATUS(ndev), status,
+				  status == NEUTRON_FW_STATUS_RESET,
+				  100, 100 * USEC_PER_MSEC);
+}
+
+void neutron_mbox_read_state(struct neutron_device *ndev, struct neutron_mbox_state *state)
+{
+	state->status = readl_relaxed(NEUTRON_MBOX_FW_STATUS(ndev));
+	state->err_code = readl_relaxed(NEUTRON_MBOX_FW_ERRCODE(ndev));
+}
diff --git a/drivers/accel/neutron/neutron_mailbox.h b/drivers/accel/neutron/neutron_mailbox.h
new file mode 100644
index 000000000000..4fe40a2f6a0c
--- /dev/null
+++ b/drivers/accel/neutron/neutron_mailbox.h
@@ -0,0 +1,42 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/* Copyright 2023, 2025-2026 NXP */
+
+#ifndef __NEUTRON_MAILBOX_H__
+#define __NEUTRON_MAILBOX_H__
+
+#include <linux/types.h>
+
+struct neutron_device;
+
+/* Device (firmware) status magic values */
+enum neutron_mbox_fwstat {
+	NEUTRON_FW_STATUS_RESET		= 0,
+	NEUTRON_FW_STATUS_ACK		= 0xA3,
+	NEUTRON_FW_STATUS_DONE		= 0xAD0,
+};
+
+/* Firmware command opcodes */
+enum neutron_mbox_cmdid {
+	NEUTRON_CMD_INFERENCE		= 0x269,
+	NEUTRON_CMD_RESET_STATE		= 0x23637,
+};
+
+#define NEUTRON_MBOX_MAX_CMD_ARGS	4
+
+/* Firmware command */
+struct neutron_mbox_cmd {
+	enum neutron_mbox_cmdid id;
+	u32 args[NEUTRON_MBOX_MAX_CMD_ARGS];
+};
+
+/* Device state */
+struct neutron_mbox_state {
+	enum neutron_mbox_fwstat status;
+	u32 err_code;
+};
+
+int neutron_mbox_send_cmd(struct neutron_device *ndev, struct neutron_mbox_cmd *cmd);
+void neutron_mbox_read_state(struct neutron_device *ndev, struct neutron_mbox_state *state);
+int neutron_mbox_reset_state(struct neutron_device *ndev);
+
+#endif /* __NEUTRON_MAILBOX_H__ */

-- 
2.34.1