mailbox: add i.MX Messaging Unit (MU) driver

This patch provides a driver for i.MX Messaging Unit (MU) using the
commom mailbox framework.

This is ported from Linux (v6.12.8) driver
drivers/mailbox/imx-mailbox.c. Its commit SHA is:
39d7d6177f0c ("mailbox: imx: use device name in interrupt name")

Signed-off-by: Viorel Suman <viorel.suman@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Alice Guo <alice.guo@nxp.com>
Reviewed-by: Ye Li <ye.li@nxp.com>

MAINTAINERS

@@ -315,6 +315,7 @@ F:	board/freescale/*mx*/
 F:	board/freescale/common/
 F:	common/spl/spl_imx_container.c
 F:	doc/imx/
+F:	drivers/mailbox/imx-mailbox.c
 F:	drivers/serial/serial_mxc.c
 F:	include/imx_container.h
 

drivers/mailbox/Kconfig

@@ -21,6 +21,13 @@ config APPLE_MBOX
 	  such as the System Management Controller (SMC) and NVMe and this
 	  driver is required to get that functionality up and running.
 
+config IMX_MU_MBOX
+	bool "Enable i.MX MU MBOX support"
+	depends on DM_MAILBOX
+	help
+	  Enable support for i.MX Messaging Unit for communication with other
+	  processors on the SoC using mailbox interface
+
 config SANDBOX_MBOX
 	bool "Enable the sandbox mailbox test driver"
 	depends on DM_MAILBOX && SANDBOX

drivers/mailbox/Makefile

@@ -5,6 +5,7 @@
 
 obj-$(CONFIG_$(XPL_)DM_MAILBOX) += mailbox-uclass.o
 obj-$(CONFIG_APPLE_MBOX) += apple-mbox.o
+obj-$(CONFIG_IMX_MU_MBOX) += imx-mailbox.o
 obj-$(CONFIG_SANDBOX_MBOX) += sandbox-mbox.o
 obj-$(CONFIG_SANDBOX_MBOX) += sandbox-mbox-test.o
 obj-$(CONFIG_STM32_IPCC) += stm32-ipcc.o

drivers/mailbox/imx-mailbox.c

@@ -0,0 +1,443 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright 2025 NXP
+ */
+
+#include <asm/io.h>
+#include <dm.h>
+#include <dm/device_compat.h>
+#include <mailbox-uclass.h>
+#include <linux/bitfield.h>
+#include <linux/bug.h>
+#include <linux/iopoll.h>
+#include <linux/compat.h>
+
+/* This driver only exposes the status bits to keep with the
+ * polling methodology of u-boot.
+ */
+DECLARE_GLOBAL_DATA_PTR;
+
+#define IMX_MU_CHANS		24
+
+#define IMX_MU_V2_PAR_OFF	0x4
+#define IMX_MU_V2_TR_MASK	GENMASK(7, 0)
+#define IMX_MU_V2_RR_MASK	GENMASK(15, 8)
+
+enum imx_mu_chan_type {
+	IMX_MU_TYPE_TX          = 0, /* Tx */
+	IMX_MU_TYPE_RX          = 1, /* Rx */
+	IMX_MU_TYPE_TXDB        = 2, /* Tx doorbell */
+	IMX_MU_TYPE_RXDB        = 3, /* Rx doorbell */
+	IMX_MU_TYPE_RST         = 4, /* Reset */
+	IMX_MU_TYPE_TXDB_V2     = 5, /* Tx doorbell with S/W ACK */
+};
+
+enum imx_mu_xcr {
+	IMX_MU_CR,
+	IMX_MU_GIER,
+	IMX_MU_GCR,
+	IMX_MU_TCR,
+	IMX_MU_RCR,
+	IMX_MU_xCR_MAX,
+};
+
+enum imx_mu_xsr {
+	IMX_MU_SR,
+	IMX_MU_GSR,
+	IMX_MU_TSR,
+	IMX_MU_RSR,
+	IMX_MU_xSR_MAX,
+};
+
+struct imx_mu_con_priv {
+	unsigned int		idx;
+	enum imx_mu_chan_type	type;
+	struct mbox_chan	*chan;
+};
+
+enum imx_mu_type {
+	IMX_MU_V1,
+	IMX_MU_V2 = BIT(1),
+	IMX_MU_V2_S4 = BIT(15),
+	IMX_MU_V2_IRQ = BIT(16),
+};
+
+struct imx_mu {
+	void __iomem *base;
+	const struct imx_mu_dcfg *dcfg;
+	u32 num_tr;
+	u32 num_rr;
+	/* use pointers to channel as a way to reserve channels */
+	struct mbox_chan *channels[IMX_MU_CHANS];
+	struct imx_mu_con_priv  con_priv[IMX_MU_CHANS];
+};
+
+struct imx_mu_dcfg {
+	int (*tx)(struct imx_mu *plat, struct imx_mu_con_priv *cp, const void *data);
+	int (*rx)(struct imx_mu *plat, struct imx_mu_con_priv *cp);
+	int (*rxdb)(struct imx_mu *plat, struct imx_mu_con_priv *cp);
+	int (*init)(struct imx_mu *plat);
+	int (*of_xlate)(struct mbox_chan *chan, struct ofnode_phandle_args *args);
+	enum imx_mu_type type;
+	u32	xTR;			/* Transmit Register0 */
+	u32	xRR;			/* Receive Register0 */
+	u32	xSR[IMX_MU_xSR_MAX];	/* Status Registers */
+	u32	xCR[IMX_MU_xCR_MAX];	/* Control Registers */
+};
+
+#define IMX_MU_xSR_GIPn(type, x) (type & IMX_MU_V2 ? BIT(x) : BIT(28 + (3 - (x))))
+#define IMX_MU_xSR_RFn(type, x) (type & IMX_MU_V2 ? BIT(x) : BIT(24 + (3 - (x))))
+#define IMX_MU_xSR_TEn(type, x) (type & IMX_MU_V2 ? BIT(x) : BIT(20 + (3 - (x))))
+
+/* General Purpose Interrupt Enable */
+#define IMX_MU_xCR_GIEn(type, x) (type & IMX_MU_V2 ? BIT(x) : BIT(28 + (3 - (x))))
+/* Receive Interrupt Enable */
+#define IMX_MU_xCR_RIEn(type, x) (type & IMX_MU_V2 ? BIT(x) : BIT(24 + (3 - (x))))
+/* Transmit Interrupt Enable */
+#define IMX_MU_xCR_TIEn(type, x) (type & IMX_MU_V2 ? BIT(x) : BIT(20 + (3 - (x))))
+/* General Purpose Interrupt Request */
+#define IMX_MU_xCR_GIRn(type, x) (type & IMX_MU_V2 ? BIT(x) : BIT(16 + (3 - (x))))
+/* MU reset */
+#define IMX_MU_xCR_RST(type)	(type & IMX_MU_V2 ? BIT(0) : BIT(5))
+#define IMX_MU_xSR_RST(type)	(type & IMX_MU_V2 ? BIT(0) : BIT(7))
+
+static void imx_mu_write(struct imx_mu *plat, u32 val, u32 offs)
+{
+	iowrite32(val, plat->base + offs);
+}
+
+static u32 imx_mu_read(struct imx_mu *plat, u32 offs)
+{
+	return ioread32(plat->base + offs);
+}
+
+static u32 imx_mu_xcr_rmw(struct imx_mu *plat, enum imx_mu_xcr type, u32 set, u32 clr)
+{
+	u32 val;
+
+	val = imx_mu_read(plat, plat->dcfg->xCR[type]);
+	val &= ~clr;
+	val |= set;
+	imx_mu_write(plat, val, plat->dcfg->xCR[type]);
+
+	return val;
+}
+
+/* check that the channel is open or owned by caller */
+static int imx_mu_check_channel(struct mbox_chan *chan)
+{
+	struct imx_mu *plat = dev_get_plat(chan->dev);
+
+	if (plat->channels[chan->id]) {
+		/* if reserved check that caller owns */
+		if (plat->channels[chan->id] == chan)
+			return 1; /* caller owns the channel */
+
+		return -EACCES;
+	}
+
+	return 0; /* channel empty */
+}
+
+static int imx_mu_chan_request(struct mbox_chan *chan)
+{
+	struct imx_mu *plat = dev_get_plat(chan->dev);
+	struct imx_mu_con_priv *cp;
+	enum imx_mu_chan_type type;
+	int idx;
+
+	type = chan->id / 4;
+	idx = chan->id % 4;
+
+	if (imx_mu_check_channel(chan) < 0) /* check if channel already in use */
+		return -EPERM;
+
+	plat->channels[chan->id] = chan;
+	chan->con_priv = kcalloc(1, sizeof(struct imx_mu_con_priv), 0);
+	if (!chan->con_priv)
+		return -ENOMEM;
+	cp = chan->con_priv;
+	cp->idx = idx;
+	cp->type = type;
+	cp->chan = chan;
+
+	switch (type) {
+	case IMX_MU_TYPE_RX:
+		imx_mu_xcr_rmw(plat, IMX_MU_RCR, IMX_MU_xCR_RIEn(plat->dcfg->type, idx), 0);
+		break;
+	case IMX_MU_TYPE_TXDB_V2:
+	case IMX_MU_TYPE_TXDB:
+	case IMX_MU_TYPE_RXDB:
+		imx_mu_xcr_rmw(plat, IMX_MU_GIER, IMX_MU_xCR_GIEn(plat->dcfg->type, idx), 0);
+		break;
+	default:
+		break;
+	}
+
+	return 0;
+}
+
+static int imx_mu_chan_free(struct mbox_chan *chan)
+{
+	struct imx_mu *plat = dev_get_plat(chan->dev);
+	struct imx_mu_con_priv *cp = chan->con_priv;
+
+	if (imx_mu_check_channel(chan) <= 0) /* check that the channel is also not empty */
+		return -EINVAL;
+
+	/* if you own channel and  channel is NOT empty */
+	plat->channels[chan->id] = NULL;
+	switch (cp->type) {
+	case IMX_MU_TYPE_TX:
+		imx_mu_xcr_rmw(plat, IMX_MU_TCR, 0, IMX_MU_xCR_TIEn(plat->dcfg->type, cp->idx));
+		break;
+	case IMX_MU_TYPE_RX:
+		imx_mu_xcr_rmw(plat, IMX_MU_RCR, 0, IMX_MU_xCR_RIEn(plat->dcfg->type, cp->idx));
+		break;
+	case IMX_MU_TYPE_TXDB_V2:
+	case IMX_MU_TYPE_TXDB:
+	case IMX_MU_TYPE_RXDB:
+		imx_mu_xcr_rmw(plat, IMX_MU_GIER, 0, IMX_MU_xCR_GIEn(plat->dcfg->type, cp->idx));
+		break;
+	default:
+		break;
+	}
+
+	kfree(cp);
+
+	return 0;
+}
+
+static int imx_mu_send(struct mbox_chan *chan, const void *data)
+{
+	struct imx_mu *plat = dev_get_plat(chan->dev);
+	struct imx_mu_con_priv *cp = chan->con_priv;
+
+	if (imx_mu_check_channel(chan) < 1) /* return if channel isn't owned */
+		return -EPERM;
+
+	return plat->dcfg->tx(plat, cp, data);
+}
+
+static int imx_mu_recv(struct mbox_chan *chan, void *data)
+{
+	struct imx_mu *plat = dev_get_plat(chan->dev);
+	struct imx_mu_con_priv *cp = chan->con_priv;
+	u32 ctrl, val;
+
+	if (imx_mu_check_channel(chan) < 1) /* return if channel isn't owned */
+		return -EPERM;
+
+	switch (cp->type) {
+	case IMX_MU_TYPE_TXDB_V2:
+	case IMX_MU_TYPE_RXDB:
+		/* check if GSR[GIRn] bit is set */
+		if (readx_poll_timeout(ioread32, plat->base + plat->dcfg->xSR[IMX_MU_GSR],
+			val, val & BIT(cp->idx), 1000000) < 0)
+			return -EBUSY;
+
+		ctrl = imx_mu_read(plat, plat->dcfg->xCR[IMX_MU_GIER]);
+		val = imx_mu_read(plat, plat->dcfg->xSR[IMX_MU_GSR]);
+		val &= IMX_MU_xSR_GIPn(plat->dcfg->type, cp->idx) &
+			(ctrl & IMX_MU_xCR_GIEn(plat->dcfg->type, cp->idx));
+		break;
+	default:
+		dev_warn(chan->dev, "Unhandled channel type %d\n", cp->type);
+		return -EOPNOTSUPP;
+	};
+
+	if (val == IMX_MU_xSR_GIPn(plat->dcfg->type, cp->idx))
+		plat->dcfg->rxdb(plat, cp);
+
+	return 0;
+}
+
+static int imx_mu_of_to_plat(struct udevice *dev)
+{
+	struct imx_mu *plat = dev_get_plat(dev);
+	fdt_addr_t addr;
+
+	addr = dev_read_addr(dev);
+	if (addr == FDT_ADDR_T_NONE)
+		return -ENODEV;
+
+	plat->base = (struct mu_type *)addr;
+
+	return 0;
+}
+
+static int imx_mu_init_generic(struct imx_mu *plat)
+{
+	unsigned int i;
+	unsigned int val;
+
+	if (plat->num_rr > 4 || plat->num_tr > 4) {
+		WARN_ONCE(true, "%s not support TR/RR larger than 4\n", __func__);
+		return -EOPNOTSUPP;
+	}
+
+	/* Set default MU configuration */
+	for (i = 0; i < IMX_MU_xCR_MAX; i++)
+		imx_mu_write(plat, 0, plat->dcfg->xCR[i]);
+
+	/* Clear any pending GIP */
+	val = imx_mu_read(plat, plat->dcfg->xSR[IMX_MU_GSR]);
+	imx_mu_write(plat, val, plat->dcfg->xSR[IMX_MU_GSR]);
+
+	/* Clear any pending RSR */
+	for (i = 0; i < plat->num_rr; i++)
+		imx_mu_read(plat, plat->dcfg->xRR + i * 4);
+
+	return 0;
+}
+
+static int imx_mu_generic_of_xlate(struct mbox_chan *chan, struct ofnode_phandle_args *args)
+{
+	enum imx_mu_chan_type type;
+	int idx, cid;
+
+	if (args->args_count != 2) {
+		dev_err(chan->dev, "Invalid argument count %d\n", args->args_count);
+		return -EINVAL;
+	}
+
+	type = args->args[0]; /* channel type */
+	idx = args->args[1]; /* index */
+
+	cid = type * 4 + idx;
+	if (cid >= IMX_MU_CHANS) {
+		dev_err(chan->dev, "Not supported channel number: %d. (type: %d, idx: %d)\n",
+			cid, type, idx);
+		return -EINVAL;
+	}
+
+	chan->id = cid;
+
+	return 0;
+}
+
+static int imx_mu_generic_tx(struct imx_mu *plat, struct imx_mu_con_priv *cp,
+			     const void *data)
+{
+	switch (cp->type) {
+	case IMX_MU_TYPE_TXDB_V2:
+		imx_mu_xcr_rmw(plat, IMX_MU_GCR, IMX_MU_xCR_GIRn(plat->dcfg->type, cp->idx), 0);
+		break;
+	default:
+		dev_warn(cp->chan->dev, "Send data on wrong channel type: %d\n", cp->type);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int imx_mu_generic_rxdb(struct imx_mu *plat, struct imx_mu_con_priv *cp)
+{
+	imx_mu_write(plat, IMX_MU_xSR_GIPn(plat->dcfg->type, cp->idx),
+		     plat->dcfg->xSR[IMX_MU_GSR]);
+
+	return 0;
+}
+
+static const struct imx_mu_dcfg imx_mu_cfg_imx6sx = {
+	.tx	= imx_mu_generic_tx,
+	.rxdb	= imx_mu_generic_rxdb,
+	.init	= imx_mu_init_generic,
+	.of_xlate = imx_mu_generic_of_xlate,
+	.type	= IMX_MU_V1,
+	.xTR	= 0x0,
+	.xRR	= 0x10,
+	.xSR	= {0x20, 0x20, 0x20, 0x20},
+	.xCR	= {0x24, 0x24, 0x24, 0x24, 0x24},
+};
+
+static const struct imx_mu_dcfg imx_mu_cfg_imx7ulp = {
+	.tx	= imx_mu_generic_tx,
+	.rxdb	= imx_mu_generic_rxdb,
+	.init	= imx_mu_init_generic,
+	.of_xlate = imx_mu_generic_of_xlate,
+	.type	= IMX_MU_V1,
+	.xTR	= 0x20,
+	.xRR	= 0x40,
+	.xSR	= {0x60, 0x60, 0x60, 0x60},
+	.xCR	= {0x64, 0x64, 0x64, 0x64, 0x64},
+};
+
+static const struct imx_mu_dcfg imx_mu_cfg_imx95 = {
+	.tx	= imx_mu_generic_tx,
+	.rxdb	= imx_mu_generic_rxdb,
+	.init	= imx_mu_init_generic,
+	.of_xlate = imx_mu_generic_of_xlate,
+	.type	= IMX_MU_V2,
+	.xTR	= 0x200,
+	.xRR	= 0x280,
+	.xSR	= {0xC, 0x118, 0x124, 0x12C},
+	.xCR	= {0x8, 0x110, 0x114, 0x120, 0x128},
+};
+
+static const struct udevice_id ids[] = {
+	{ .compatible = "fsl,imx6sx-mu", .data = (ulong)&imx_mu_cfg_imx6sx },
+	{ .compatible = "fsl,imx7ulp-mu", .data = (ulong)&imx_mu_cfg_imx7ulp },
+	{ .compatible = "fsl,imx95-mu", .data = (ulong)&imx_mu_cfg_imx95 },
+	{ }
+};
+
+int imx_mu_of_xlate(struct mbox_chan *chan, struct ofnode_phandle_args *args)
+{
+	struct imx_mu *plat = dev_get_plat(chan->dev);
+
+	return plat->dcfg->of_xlate(chan, args);
+}
+
+struct mbox_ops imx_mu_ops = {
+	.of_xlate = imx_mu_of_xlate,
+	.request  = imx_mu_chan_request,
+	.rfree    = imx_mu_chan_free,
+	.send     = imx_mu_send,
+	.recv     = imx_mu_recv,
+};
+
+static void imx_mu_get_tr_rr(struct imx_mu *plat)
+{
+	u32 val;
+
+	if (plat->dcfg->type & IMX_MU_V2) {
+		val = imx_mu_read(plat, IMX_MU_V2_PAR_OFF);
+		plat->num_tr = FIELD_GET(IMX_MU_V2_TR_MASK, val);
+		plat->num_rr = FIELD_GET(IMX_MU_V2_RR_MASK, val);
+	} else {
+		plat->num_tr = 4;
+		plat->num_rr = 4;
+	}
+}
+
+static int imx_mu_probe(struct udevice *dev)
+{
+	struct imx_mu *plat = dev_get_plat(dev);
+	int ret;
+
+	debug("%s(dev=%p)\n", __func__, dev);
+
+	plat->dcfg = (void *)dev_get_driver_data(dev);
+
+	imx_mu_get_tr_rr(plat);
+
+	ret = plat->dcfg->init(plat);
+	if (ret) {
+		dev_err(dev, "Failed to init MU\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+U_BOOT_DRIVER(imx_mu) = {
+	.name = "imx-mu",
+	.id = UCLASS_MAILBOX,
+	.of_match = ids,
+	.of_to_plat = imx_mu_of_to_plat,
+	.plat_auto = sizeof(struct imx_mu),
+	.probe = imx_mu_probe,
+	.ops = &imx_mu_ops,
+	.flags = DM_FLAG_PRE_RELOC,
+};