linux/drivers/mailbox/imx-mailbox.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2018 Pengutronix, Oleksij Rempel <o.rempel@pengutronix.de>
 */

#include <linux/clk.h>
#include <linux/firmware/imx/ipc.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/iopoll.h>
#include <linux/kernel.h>
#include <linux/mailbox_controller.h>
#include <linux/module.h>
#include <linux/of_device.h>
#include <linux/pm_runtime.h>
#include <linux/slab.h>

#define IMX_MU_CHANS		16
/* TX0/RX0/RXDB[0-3] */
#define IMX_MU_SCU_CHANS	6
#define IMX_MU_CHAN_NAME_SIZE	20

enum imx_mu_chan_type {
	IMX_MU_TYPE_TX,		/* Tx */
	IMX_MU_TYPE_RX,		/* Rx */
	IMX_MU_TYPE_TXDB,	/* Tx doorbell */
	IMX_MU_TYPE_RXDB,	/* Rx doorbell */
};

enum imx_mu_xcr {
	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,
};

struct imx_sc_rpc_msg_max {
	struct imx_sc_rpc_msg hdr;
	u32 data[7];
};

struct imx_mu_con_priv {
	unsigned int		idx;
	char			irq_desc[IMX_MU_CHAN_NAME_SIZE];
	enum imx_mu_chan_type	type;
	struct mbox_chan	*chan;
	struct tasklet_struct	txdb_tasklet;
};

struct imx_mu_priv {
	struct device		*dev;
	void __iomem		*base;
	spinlock_t		xcr_lock; /* control register lock */

	struct mbox_controller	mbox;
	struct mbox_chan	mbox_chans[IMX_MU_CHANS];

	struct imx_mu_con_priv  con_priv[IMX_MU_CHANS];
	const struct imx_mu_dcfg	*dcfg;
	struct clk		*clk;
	int			irq;

	u32 xcr[4];

	bool			side_b;
};

enum imx_mu_type {
	IMX_MU_V1,
	IMX_MU_V2,
};

struct imx_mu_dcfg {
	int (*tx)(struct imx_mu_priv *priv, struct imx_mu_con_priv *cp, void *data);
	int (*rx)(struct imx_mu_priv *priv, struct imx_mu_con_priv *cp);
	void (*init)(struct imx_mu_priv *priv);
	enum imx_mu_type type;
	u32	xTR;		/* Transmit Register0 */
	u32	xRR;		/* Receive Register0 */
	u32	xSR[4];		/* Status Registers */
	u32	xCR[4];		/* 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))))


static struct imx_mu_priv *to_imx_mu_priv(struct mbox_controller *mbox)
{
	return container_of(mbox, struct imx_mu_priv, mbox);
}

static void imx_mu_write(struct imx_mu_priv *priv, u32 val, u32 offs)
{
	iowrite32(val, priv->base + offs);
}

static u32 imx_mu_read(struct imx_mu_priv *priv, u32 offs)
{
	return ioread32(priv->base + offs);
}

static u32 imx_mu_xcr_rmw(struct imx_mu_priv *priv, enum imx_mu_xcr type, u32 set, u32 clr)
{
	unsigned long flags;
	u32 val;

	spin_lock_irqsave(&priv->xcr_lock, flags);
	val = imx_mu_read(priv, priv->dcfg->xCR[type]);
	val &= ~clr;
	val |= set;
	imx_mu_write(priv, val, priv->dcfg->xCR[type]);
	spin_unlock_irqrestore(&priv->xcr_lock, flags);

	return val;
}

static int imx_mu_generic_tx(struct imx_mu_priv *priv,
			     struct imx_mu_con_priv *cp,
			     void *data)
{
	u32 *arg = data;

	switch (cp->type) {
	case IMX_MU_TYPE_TX:
		imx_mu_write(priv, *arg, priv->dcfg->xTR + cp->idx * 4);
		imx_mu_xcr_rmw(priv, IMX_MU_TCR, IMX_MU_xCR_TIEn(priv->dcfg->type, cp->idx), 0);
		break;
	case IMX_MU_TYPE_TXDB:
		imx_mu_xcr_rmw(priv, IMX_MU_GCR, IMX_MU_xCR_GIRn(priv->dcfg->type, cp->idx), 0);
		tasklet_schedule(&cp->txdb_tasklet);
		break;
	default:
		dev_warn_ratelimited(priv->dev, "Send data on wrong channel type: %d\n", cp->type);
		return -EINVAL;
	}

	return 0;
}

static int imx_mu_generic_rx(struct imx_mu_priv *priv,
			     struct imx_mu_con_priv *cp)
{
	u32 dat;

	dat = imx_mu_read(priv, priv->dcfg->xRR + (cp->idx) * 4);
	mbox_chan_received_data(cp->chan, (void *)&dat);

	return 0;
}

static int imx_mu_scu_tx(struct imx_mu_priv *priv,
			 struct imx_mu_con_priv *cp,
			 void *data)
{
	struct imx_sc_rpc_msg_max *msg = data;
	u32 *arg = data;
	int i, ret;
	u32 xsr;

	switch (cp->type) {
	case IMX_MU_TYPE_TX:
		/*
		 * msg->hdr.size specifies the number of u32 words while
		 * sizeof yields bytes.
		 */

		if (msg->hdr.size > sizeof(*msg) / 4) {
			/*
			 * The real message size can be different to
			 * struct imx_sc_rpc_msg_max size
			 */
			dev_err(priv->dev, "Maximal message size (%zu bytes) exceeded on TX; got: %i bytes\n", sizeof(*msg), msg->hdr.size << 2);
			return -EINVAL;
		}

		for (i = 0; i < 4 && i < msg->hdr.size; i++)
			imx_mu_write(priv, *arg++, priv->dcfg->xTR + (i % 4) * 4);
		for (; i < msg->hdr.size; i++) {
			ret = readl_poll_timeout(priv->base + priv->dcfg->xSR[IMX_MU_TSR],
						 xsr,
						 xsr & IMX_MU_xSR_TEn(priv->dcfg->type, i % 4),
						 0, 100);
			if (ret) {
				dev_err(priv->dev, "Send data index: %d timeout\n", i);
				return ret;
			}
			imx_mu_write(priv, *arg++, priv->dcfg->xTR + (i % 4) * 4);
		}

		imx_mu_xcr_rmw(priv, IMX_MU_TCR, IMX_MU_xCR_TIEn(priv->dcfg->type, cp->idx), 0);
		break;
	default:
		dev_warn_ratelimited(priv->dev, "Send data on wrong channel type: %d\n", cp->type);
		return -EINVAL;
	}

	return 0;
}

static int imx_mu_scu_rx(struct imx_mu_priv *priv,
			 struct imx_mu_con_priv *cp)
{
	struct imx_sc_rpc_msg_max msg;
	u32 *data = (u32 *)&msg;
	int i, ret;
	u32 xsr;

	imx_mu_xcr_rmw(priv, IMX_MU_RCR, 0, IMX_MU_xCR_RIEn(priv->dcfg->type, 0));
	*data++ = imx_mu_read(priv, priv->dcfg->xRR);

	if (msg.hdr.size > sizeof(msg) / 4) {
		dev_err(priv->dev, "Maximal message size (%zu bytes) exceeded on RX; got: %i bytes\n", sizeof(msg), msg.hdr.size << 2);
		return -EINVAL;
	}

	for (i = 1; i < msg.hdr.size; i++) {
		ret = readl_poll_timeout(priv->base + priv->dcfg->xSR[IMX_MU_RSR], xsr,
					 xsr & IMX_MU_xSR_RFn(priv->dcfg->type, i % 4), 0, 100);
		if (ret) {
			dev_err(priv->dev, "timeout read idx %d\n", i);
			return ret;
		}
		*data++ = imx_mu_read(priv, priv->dcfg->xRR + (i % 4) * 4);
	}

	imx_mu_xcr_rmw(priv, IMX_MU_RCR, IMX_MU_xCR_RIEn(priv->dcfg->type, 0), 0);
	mbox_chan_received_data(cp->chan, (void *)&msg);

	return 0;
}

static void imx_mu_txdb_tasklet(unsigned long data)
{
	struct imx_mu_con_priv *cp = (struct imx_mu_con_priv *)data;

	mbox_chan_txdone(cp->chan, 0);
}

static irqreturn_t imx_mu_isr(int irq, void *p)
{
	struct mbox_chan *chan = p;
	struct imx_mu_priv *priv = to_imx_mu_priv(chan->mbox);
	struct imx_mu_con_priv *cp = chan->con_priv;
	u32 val, ctrl;

	switch (cp->type) {
	case IMX_MU_TYPE_TX:
		ctrl = imx_mu_read(priv, priv->dcfg->xCR[IMX_MU_TCR]);
		val = imx_mu_read(priv, priv->dcfg->xSR[IMX_MU_TSR]);
		val &= IMX_MU_xSR_TEn(priv->dcfg->type, cp->idx) &
			(ctrl & IMX_MU_xCR_TIEn(priv->dcfg->type, cp->idx));
		break;
	case IMX_MU_TYPE_RX:
		ctrl = imx_mu_read(priv, priv->dcfg->xCR[IMX_MU_RCR]);
		val = imx_mu_read(priv, priv->dcfg->xSR[IMX_MU_RSR]);
		val &= IMX_MU_xSR_RFn(priv->dcfg->type, cp->idx) &
			(ctrl & IMX_MU_xCR_RIEn(priv->dcfg->type, cp->idx));
		break;
	case IMX_MU_TYPE_RXDB:
		ctrl = imx_mu_read(priv, priv->dcfg->xCR[IMX_MU_GIER]);
		val = imx_mu_read(priv, priv->dcfg->xSR[IMX_MU_GSR]);
		val &= IMX_MU_xSR_GIPn(priv->dcfg->type, cp->idx) &
			(ctrl & IMX_MU_xCR_GIEn(priv->dcfg->type, cp->idx));
		break;
	default:
		dev_warn_ratelimited(priv->dev, "Unhandled channel type %d\n",
				     cp->type);
		return IRQ_NONE;
	}

	if (!val)
		return IRQ_NONE;

	if ((val == IMX_MU_xSR_TEn(priv->dcfg->type, cp->idx)) &&
	    (cp->type == IMX_MU_TYPE_TX)) {
		imx_mu_xcr_rmw(priv, IMX_MU_TCR, 0, IMX_MU_xCR_TIEn(priv->dcfg->type, cp->idx));
		mbox_chan_txdone(chan, 0);
	} else if ((val == IMX_MU_xSR_RFn(priv->dcfg->type, cp->idx)) &&
		   (cp->type == IMX_MU_TYPE_RX)) {
		priv->dcfg->rx(priv, cp);
	} else if ((val == IMX_MU_xSR_GIPn(priv->dcfg->type, cp->idx)) &&
		   (cp->type == IMX_MU_TYPE_RXDB)) {
		imx_mu_write(priv, IMX_MU_xSR_GIPn(priv->dcfg->type, cp->idx),
			     priv->dcfg->xSR[IMX_MU_GSR]);
		mbox_chan_received_data(chan, NULL);
	} else {
		dev_warn_ratelimited(priv->dev, "Not handled interrupt\n");
		return IRQ_NONE;
	}

	return IRQ_HANDLED;
}

static int imx_mu_send_data(struct mbox_chan *chan, void *data)
{
	struct imx_mu_priv *priv = to_imx_mu_priv(chan->mbox);
	struct imx_mu_con_priv *cp = chan->con_priv;

	return priv->dcfg->tx(priv, cp, data);
}

static int imx_mu_startup(struct mbox_chan *chan)
{
	struct imx_mu_priv *priv = to_imx_mu_priv(chan->mbox);
	struct imx_mu_con_priv *cp = chan->con_priv;
	unsigned long irq_flag = IRQF_SHARED;
	int ret;

	pm_runtime_get_sync(priv->dev);
	if (cp->type == IMX_MU_TYPE_TXDB) {
		/* Tx doorbell don't have ACK support */
		tasklet_init(&cp->txdb_tasklet, imx_mu_txdb_tasklet,
			     (unsigned long)cp);
		return 0;
	}

	/* IPC MU should be with IRQF_NO_SUSPEND set */
	if (!priv->dev->pm_domain)
		irq_flag |= IRQF_NO_SUSPEND;

	ret = request_irq(priv->irq, imx_mu_isr, irq_flag,
			  cp->irq_desc, chan);
	if (ret) {
		dev_err(priv->dev,
			"Unable to acquire IRQ %d\n", priv->irq);
		return ret;
	}

	switch (cp->type) {
	case IMX_MU_TYPE_RX:
		imx_mu_xcr_rmw(priv, IMX_MU_RCR, IMX_MU_xCR_RIEn(priv->dcfg->type, cp->idx), 0);
		break;
	case IMX_MU_TYPE_RXDB:
		imx_mu_xcr_rmw(priv, IMX_MU_GIER, IMX_MU_xCR_GIEn(priv->dcfg->type, cp->idx), 0);
		break;
	default:
		break;
	}

	return 0;
}

static void imx_mu_shutdown(struct mbox_chan *chan)
{
	struct imx_mu_priv *priv = to_imx_mu_priv(chan->mbox);
	struct imx_mu_con_priv *cp = chan->con_priv;

	if (cp->type == IMX_MU_TYPE_TXDB) {
		tasklet_kill(&cp->txdb_tasklet);
		pm_runtime_put_sync(priv->dev);
		return;
	}

	switch (cp->type) {
	case IMX_MU_TYPE_TX:
		imx_mu_xcr_rmw(priv, IMX_MU_TCR, 0, IMX_MU_xCR_TIEn(priv->dcfg->type, cp->idx));
		break;
	case IMX_MU_TYPE_RX:
		imx_mu_xcr_rmw(priv, IMX_MU_RCR, 0, IMX_MU_xCR_RIEn(priv->dcfg->type, cp->idx));
		break;
	case IMX_MU_TYPE_RXDB:
		imx_mu_xcr_rmw(priv, IMX_MU_GIER, 0, IMX_MU_xCR_GIEn(priv->dcfg->type, cp->idx));
		break;
	default:
		break;
	}

	free_irq(priv->irq, chan);
	pm_runtime_put_sync(priv->dev);
}

static const struct mbox_chan_ops imx_mu_ops = {
	.send_data = imx_mu_send_data,
	.startup = imx_mu_startup,
	.shutdown = imx_mu_shutdown,
};

static struct mbox_chan *imx_mu_scu_xlate(struct mbox_controller *mbox,
					  const struct of_phandle_args *sp)
{
	u32 type, idx, chan;

	if (sp->args_count != 2) {
		dev_err(mbox->dev, "Invalid argument count %d\n", sp->args_count);
		return ERR_PTR(-EINVAL);
	}

	type = sp->args[0]; /* channel type */
	idx = sp->args[1]; /* index */

	switch (type) {
	case IMX_MU_TYPE_TX:
	case IMX_MU_TYPE_RX:
		if (idx != 0)
			dev_err(mbox->dev, "Invalid chan idx: %d\n", idx);
		chan = type;
		break;
	case IMX_MU_TYPE_RXDB:
		chan = 2 + idx;
		break;
	default:
		dev_err(mbox->dev, "Invalid chan type: %d\n", type);
		return ERR_PTR(-EINVAL);
	}

	if (chan >= mbox->num_chans) {
		dev_err(mbox->dev, "Not supported channel number: %d. (type: %d, idx: %d)\n", chan, type, idx);
		return ERR_PTR(-EINVAL);
	}

	return &mbox->chans[chan];
}

static struct mbox_chan * imx_mu_xlate(struct mbox_controller *mbox,
				       const struct of_phandle_args *sp)
{
	u32 type, idx, chan;

	if (sp->args_count != 2) {
		dev_err(mbox->dev, "Invalid argument count %d\n", sp->args_count);
		return ERR_PTR(-EINVAL);
	}

	type = sp->args[0]; /* channel type */
	idx = sp->args[1]; /* index */
	chan = type * 4 + idx;

	if (chan >= mbox->num_chans) {
		dev_err(mbox->dev, "Not supported channel number: %d. (type: %d, idx: %d)\n", chan, type, idx);
		return ERR_PTR(-EINVAL);
	}

	return &mbox->chans[chan];
}

static void imx_mu_init_generic(struct imx_mu_priv *priv)
{
	unsigned int i;

	for (i = 0; i < IMX_MU_CHANS; i++) {
		struct imx_mu_con_priv *cp = &priv->con_priv[i];

		cp->idx = i % 4;
		cp->type = i >> 2;
		cp->chan = &priv->mbox_chans[i];
		priv->mbox_chans[i].con_priv = cp;
		snprintf(cp->irq_desc, sizeof(cp->irq_desc),
			 "imx_mu_chan[%i-%i]", cp->type, cp->idx);
	}

	priv->mbox.num_chans = IMX_MU_CHANS;
	priv->mbox.of_xlate = imx_mu_xlate;

	if (priv->side_b)
		return;

	/* Set default MU configuration */
	for (i = 0; i < IMX_MU_xCR_MAX; i++)
		imx_mu_write(priv, 0, priv->dcfg->xCR[i]);
}

static void imx_mu_init_scu(struct imx_mu_priv *priv)
{
	unsigned int i;

	for (i = 0; i < IMX_MU_SCU_CHANS; i++) {
		struct imx_mu_con_priv *cp = &priv->con_priv[i];

		cp->idx = i < 2 ? 0 : i - 2;
		cp->type = i < 2 ? i : IMX_MU_TYPE_RXDB;
		cp->chan = &priv->mbox_chans[i];
		priv->mbox_chans[i].con_priv = cp;
		snprintf(cp->irq_desc, sizeof(cp->irq_desc),
			 "imx_mu_chan[%i-%i]", cp->type, cp->idx);
	}

	priv->mbox.num_chans = IMX_MU_SCU_CHANS;
	priv->mbox.of_xlate = imx_mu_scu_xlate;

	/* Set default MU configuration */
	for (i = 0; i < IMX_MU_xCR_MAX; i++)
		imx_mu_write(priv, 0, priv->dcfg->xCR[i]);
}

static int imx_mu_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	struct device_node *np = dev->of_node;
	struct imx_mu_priv *priv;
	const struct imx_mu_dcfg *dcfg;
	int ret;

	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
	if (!priv)
		return -ENOMEM;

	priv->dev = dev;

	priv->base = devm_platform_ioremap_resource(pdev, 0);
	if (IS_ERR(priv->base))
		return PTR_ERR(priv->base);

	priv->irq = platform_get_irq(pdev, 0);
	if (priv->irq < 0)
		return priv->irq;

	dcfg = of_device_get_match_data(dev);
	if (!dcfg)
		return -EINVAL;
	priv->dcfg = dcfg;

	priv->clk = devm_clk_get(dev, NULL);
	if (IS_ERR(priv->clk)) {
		if (PTR_ERR(priv->clk) != -ENOENT)
			return PTR_ERR(priv->clk);

		priv->clk = NULL;
	}

	ret = clk_prepare_enable(priv->clk);
	if (ret) {
		dev_err(dev, "Failed to enable clock\n");
		return ret;
	}

	priv->side_b = of_property_read_bool(np, "fsl,mu-side-b");

	priv->dcfg->init(priv);

	spin_lock_init(&priv->xcr_lock);

	priv->mbox.dev = dev;
	priv->mbox.ops = &imx_mu_ops;
	priv->mbox.chans = priv->mbox_chans;
	priv->mbox.txdone_irq = true;

	platform_set_drvdata(pdev, priv);

	ret = devm_mbox_controller_register(dev, &priv->mbox);
	if (ret) {
		clk_disable_unprepare(priv->clk);
		return ret;
	}

	pm_runtime_enable(dev);

	ret = pm_runtime_get_sync(dev);
	if (ret < 0) {
		pm_runtime_put_noidle(dev);
		goto disable_runtime_pm;
	}

	ret = pm_runtime_put_sync(dev);
	if (ret < 0)
		goto disable_runtime_pm;

	clk_disable_unprepare(priv->clk);

	return 0;

disable_runtime_pm:
	pm_runtime_disable(dev);
	clk_disable_unprepare(priv->clk);
	return ret;
}

static int imx_mu_remove(struct platform_device *pdev)
{
	struct imx_mu_priv *priv = platform_get_drvdata(pdev);

	pm_runtime_disable(priv->dev);

	return 0;
}

static const struct imx_mu_dcfg imx_mu_cfg_imx6sx = {
	.tx	= imx_mu_generic_tx,
	.rx	= imx_mu_generic_rx,
	.init	= imx_mu_init_generic,
	.xTR	= 0x0,
	.xRR	= 0x10,
	.xSR	= {0x20, 0x20, 0x20, 0x20},
	.xCR	= {0x24, 0x24, 0x24, 0x24},
};

static const struct imx_mu_dcfg imx_mu_cfg_imx7ulp = {
	.tx	= imx_mu_generic_tx,
	.rx	= imx_mu_generic_rx,
	.init	= imx_mu_init_generic,
	.xTR	= 0x20,
	.xRR	= 0x40,
	.xSR	= {0x60, 0x60, 0x60, 0x60},
	.xCR	= {0x64, 0x64, 0x64, 0x64},
};

static const struct imx_mu_dcfg imx_mu_cfg_imx8ulp = {
	.tx	= imx_mu_generic_tx,
	.rx	= imx_mu_generic_rx,
	.init	= imx_mu_init_generic,
	.type	= IMX_MU_V2,
	.xTR	= 0x200,
	.xRR	= 0x280,
	.xSR	= {0xC, 0x118, 0x124, 0x12C},
	.xCR	= {0x110, 0x114, 0x120, 0x128},
};

static const struct imx_mu_dcfg imx_mu_cfg_imx8_scu = {
	.tx	= imx_mu_scu_tx,
	.rx	= imx_mu_scu_rx,
	.init	= imx_mu_init_scu,
	.xTR	= 0x0,
	.xRR	= 0x10,
	.xSR	= {0x20, 0x20, 0x20, 0x20},
	.xCR	= {0x24, 0x24, 0x24, 0x24},
};

static const struct of_device_id imx_mu_dt_ids[] = {
	{ .compatible = "fsl,imx7ulp-mu", .data = &imx_mu_cfg_imx7ulp },
	{ .compatible = "fsl,imx6sx-mu", .data = &imx_mu_cfg_imx6sx },
	{ .compatible = "fsl,imx8ulp-mu", .data = &imx_mu_cfg_imx8ulp },
	{ .compatible = "fsl,imx8-mu-scu", .data = &imx_mu_cfg_imx8_scu },
	{ },
};
MODULE_DEVICE_TABLE(of, imx_mu_dt_ids);

static int __maybe_unused imx_mu_suspend_noirq(struct device *dev)
{
	struct imx_mu_priv *priv = dev_get_drvdata(dev);
	int i;

	if (!priv->clk) {
		for (i = 0; i < IMX_MU_xCR_MAX; i++)
			priv->xcr[i] = imx_mu_read(priv, priv->dcfg->xCR[i]);
	}

	return 0;
}

static int __maybe_unused imx_mu_resume_noirq(struct device *dev)
{
	struct imx_mu_priv *priv = dev_get_drvdata(dev);
	int i;

	/*
	 * ONLY restore MU when context lost, the TIE could
	 * be set during noirq resume as there is MU data
	 * communication going on, and restore the saved
	 * value will overwrite the TIE and cause MU data
	 * send failed, may lead to system freeze. This issue
	 * is observed by testing freeze mode suspend.
	 */
	if (!imx_mu_read(priv, priv->dcfg->xCR[0]) && !priv->clk) {
		for (i = 0; i < IMX_MU_xCR_MAX; i++)
			imx_mu_write(priv, priv->xcr[i], priv->dcfg->xCR[i]);
	}

	return 0;
}

static int __maybe_unused imx_mu_runtime_suspend(struct device *dev)
{
	struct imx_mu_priv *priv = dev_get_drvdata(dev);

	clk_disable_unprepare(priv->clk);

	return 0;
}

static int __maybe_unused imx_mu_runtime_resume(struct device *dev)
{
	struct imx_mu_priv *priv = dev_get_drvdata(dev);
	int ret;

	ret = clk_prepare_enable(priv->clk);
	if (ret)
		dev_err(dev, "failed to enable clock\n");

	return ret;
}

static const struct dev_pm_ops imx_mu_pm_ops = {
	SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(imx_mu_suspend_noirq,
				      imx_mu_resume_noirq)
	SET_RUNTIME_PM_OPS(imx_mu_runtime_suspend,
			   imx_mu_runtime_resume, NULL)
};

static struct platform_driver imx_mu_driver = {
	.probe		= imx_mu_probe,
	.remove		= imx_mu_remove,
	.driver = {
		.name	= "imx_mu",
		.of_match_table = imx_mu_dt_ids,
		.pm = &imx_mu_pm_ops,
	},
};
module_platform_driver(imx_mu_driver);

MODULE_AUTHOR("Oleksij Rempel <o.rempel@pengutronix.de>");
MODULE_DESCRIPTION("Message Unit driver for i.MX");
MODULE_LICENSE("GPL v2");