RE: [RFC 3/4] ARM: imx: add the platform related rpmsg implementation

[Richard Zhu]

Hi Shawn:
Thanks for your comments.
Further review would copied to Stefan Agner.

Best Regards
hongxing zhu
Linux BSP team
Office: 86-21-28937189
Email: hongxing.zhu@xxxxxxx


-----Original Message-----
From: Shawn Guo [mailto:shawnguo@xxxxxxxxxx] 
Sent: Thursday, January 28, 2016 9:35 AM
To: Richard Zhu
Cc: ohad@xxxxxxxxxx; Stefan Agner; linux-kernel@xxxxxxxxxxxxxxx
Subject: Re: [RFC 3/4] ARM: imx: add the platform related rpmsg implementation

On Wed, Jan 06, 2016 at 04:06:43PM +0800, Richard Zhu wrote:
> From: Richard Zhu <Richard.Zhu@xxxxxxxxxxxxx>
> 
> - add mu driver support, the irq and 4bytes msg of the mu module are 
> as the interaction channel between A# core and the M4 core on imx amp 
> platforms.
> - register one notify in isr of the mu's irq used by rpmsg.
> - instance the virtual processor, and fill up the virtio_config_ops in 
> the platform related rpmsg implementation codes.
> - hard-code the vring storage shared by A# core and M# core on AMP 
> SOCs.
> 
> Signed-off-by: Richard Zhu <hongxing.zhu@xxxxxxx>
> ---
>  arch/arm/mach-imx/Kconfig     |  12 ++
>  arch/arm/mach-imx/Makefile    |   2 +
>  arch/arm/mach-imx/imx_rpmsg.c | 364 ++++++++++++++++++++++++++++++++++++++++++
>  arch/arm/mach-imx/mu.c        | 217 +++++++++++++++++++++++++

I'm not rpmsg expert, but it seems to me that the driver should be put into drivers/rpmsg/ rather than mach-imx.
[Richard] This part rpmsg codes are closed related to the platform. For example, kinds of ops callback functions.
Thus, these codes are placed into arch/arm/mach-imx/ folder. BTW,  so does to omap rpmsg implementation.
http://omappedia.org/wiki/RPMsg_Kernel_Sources

Also, when you repost, you may want to copy Stefan Agner <stefan@xxxxxxxx>, who is helping maintain Vybrid platform and might be interested in your patches.

Shawn

>  include/linux/imx_rpmsg.h     |  27 ++++
>  5 files changed, 622 insertions(+)
>  create mode 100644 arch/arm/mach-imx/imx_rpmsg.c  create mode 100644 
> arch/arm/mach-imx/mu.c  create mode 100644 include/linux/imx_rpmsg.h
> 
> diff --git a/arch/arm/mach-imx/Kconfig b/arch/arm/mach-imx/Kconfig 
> index 8ceda28..a7bc41c 100644
> --- a/arch/arm/mach-imx/Kconfig
> +++ b/arch/arm/mach-imx/Kconfig
> @@ -56,6 +56,12 @@ config HAVE_IMX_GPC  config HAVE_IMX_MMDC
>  	bool
>  
> +config HAVE_IMX_MU
> +	bool
> +
> +config HAVE_IMX_RPMSG
> +	bool
> +
>  config HAVE_IMX_SRC
>  	def_bool y if SMP
>  	select ARCH_HAS_RESET_CONTROLLER
> @@ -544,6 +550,9 @@ config SOC_IMX6SX
>  	bool "i.MX6 SoloX support"
>  	select PINCTRL_IMX6SX
>  	select SOC_IMX6
> +	select HAVE_IMX_MU
> +	select HAVE_IMX_RPMSG
> +	select RPMSG
>  
>  	help
>  	  This enables support for Freescale i.MX6 SoloX processor.
> @@ -562,6 +571,9 @@ config SOC_IMX7D
>  	select ARM_GIC
>  	select HAVE_IMX_ANATOP
>  	select HAVE_IMX_MMDC
> +	select HAVE_IMX_MU
> +	select HAVE_IMX_RPMSG
> +	select RPMSG
>  	help
>  		This enables support for Freescale i.MX7 Dual processor.
>  
> diff --git a/arch/arm/mach-imx/Makefile b/arch/arm/mach-imx/Makefile 
> index fb689d8..a3c1814 100644
> --- a/arch/arm/mach-imx/Makefile
> +++ b/arch/arm/mach-imx/Makefile
> @@ -74,7 +74,9 @@ obj-$(CONFIG_MACH_IMX35_DT) += imx35-dt.o
>  obj-$(CONFIG_HAVE_IMX_ANATOP) += anatop.o
>  obj-$(CONFIG_HAVE_IMX_GPC) += gpc.o
>  obj-$(CONFIG_HAVE_IMX_MMDC) += mmdc.o
> +obj-$(CONFIG_HAVE_IMX_MU) += mu.o
>  obj-$(CONFIG_HAVE_IMX_SRC) += src.o
> +obj-$(CONFIG_HAVE_IMX_RPMSG) += imx_rpmsg.o
>  ifneq ($(CONFIG_SOC_IMX6)$(CONFIG_SOC_LS1021A),)
>  AFLAGS_headsmp.o :=-Wa,-march=armv7-a
>  obj-$(CONFIG_SMP) += headsmp.o platsmp.o diff --git 
> a/arch/arm/mach-imx/imx_rpmsg.c b/arch/arm/mach-imx/imx_rpmsg.c new 
> file mode 100644 index 0000000..ab6ba7a
> --- /dev/null
> +++ b/arch/arm/mach-imx/imx_rpmsg.c
> @@ -0,0 +1,364 @@
> +/*
> + * Copyright (C) 2016 Freescale Semiconductor, Inc.
> + *
> + * derived from the omap-rpmsg implementation.
> + *
> + * The code contained herein is licensed under the GNU General Public
> + * License. You may obtain a copy of the GNU General Public License
> + * Version 2 or later at the following locations:
> + *
> + * http://www.opensource.org/licenses/gpl-license.html
> + * http://www.gnu.org/copyleft/gpl.html
> + */
> +
> +#include <linux/err.h>
> +#include <linux/init.h>
> +#include <linux/interrupt.h>
> +#include <linux/module.h>
> +#include <linux/notifier.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/rpmsg.h>
> +#include <linux/slab.h>
> +#include <linux/virtio.h>
> +#include <linux/virtio_config.h>
> +#include <linux/virtio_ids.h>
> +#include <linux/virtio_ring.h>
> +#include <linux/imx_rpmsg.h>
> +
> +struct imx_rpmsg_vproc {
> +	struct virtio_device vdev;
> +	unsigned int vring[2];
> +	char *rproc_name;
> +	struct mutex lock;
> +	struct notifier_block nb;
> +	struct virtqueue *vq[2];
> +	int base_vq_id;
> +	int num_of_vqs;
> +};
> +
> +/*
> + * For now, allocate 256 buffers of 512 bytes for each side. each 
> +buffer
> + * will then have 16B for the msg header and 496B for the payload.
> + * This will require a total space of 256KB for the buffers 
> +themselves, and
> + * 3 pages for every vring (the size of the vring depends on the 
> +number of
> + * buffers it supports).
> + */
> +#define RPMSG_NUM_BUFS		(512)
> +#define RPMSG_BUF_SIZE		(512)
> +#define RPMSG_BUFS_SPACE	(RPMSG_NUM_BUFS * RPMSG_BUF_SIZE)
> +
> +/*
> + * The alignment between the consumer and producer parts of the vring.
> + * Note: this is part of the "wire" protocol. If you change this, you 
> +need
> + * to update your BIOS image as well
> + */
> +#define RPMSG_VRING_ALIGN	(4096)
> +
> +/* With 256 buffers, our vring will occupy 3 pages */
> +#define RPMSG_RING_SIZE	((DIV_ROUND_UP(vring_size(RPMSG_NUM_BUFS / 2, \
> +				RPMSG_VRING_ALIGN), PAGE_SIZE)) * PAGE_SIZE)
> +
> +#define to_imx_rpdev(vd) container_of(vd, struct imx_rpmsg_vproc, 
> +vdev)
> +
> +struct imx_rpmsg_vq_info {
> +	__u16 num;	/* number of entries in the virtio_ring */
> +	__u16 vq_id;	/* a globaly unique index of this virtqueue */
> +	void *addr;	/* address where we mapped the virtio ring */
> +	struct imx_rpmsg_vproc *rpdev;
> +};
> +
> +static u64 imx_rpmsg_get_features(struct virtio_device *vdev) {
> +	return 1 << VIRTIO_RPMSG_F_NS;
> +}
> +
> +static int imx_rpmsg_finalize_features(struct virtio_device *vdev) {
> +	/* Give virtio_ring a chance to accept features */
> +	vring_transport_features(vdev);
> +	return 0;
> +}
> +
> +/* kick the remote processor, and let it know which virtqueue to poke 
> +at */ static bool imx_rpmsg_notify(struct virtqueue *vq) {
> +	int ret;
> +	unsigned int mu_rpmsg = 0;
> +	struct imx_rpmsg_vq_info *rpvq = vq->priv;
> +
> +	mu_rpmsg = rpvq->vq_id << 16;
> +	mutex_lock(&rpvq->rpdev->lock);
> +	/* send the index of the triggered virtqueue as the mu payload */
> +	ret = imx_mu_rpmsg_send(mu_rpmsg);
> +	mutex_unlock(&rpvq->rpdev->lock);
> +	if (ret) {
> +		pr_err("ugh, imx_mu_rpmsg_send() failed: %d\n", ret);
> +		return false;
> +	}
> +
> +	return true;
> +}
> +
> +static int imx_mu_rpmsg_callback(struct notifier_block *this,
> +					unsigned long index, void *data) {
> +	u32 mu_msg = (u32) data;
> +	struct imx_rpmsg_vproc *rpdev;
> +
> +	rpdev = container_of(this, struct imx_rpmsg_vproc, nb);
> +
> +	pr_debug("%s mu_msg: 0x%x\n", __func__, mu_msg);
> +
> +	/* ignore vq indices which are clearly not for us */
> +	mu_msg = mu_msg >> 16;
> +	if (mu_msg < rpdev->base_vq_id)
> +		pr_err("mu_msg: 0x%x is invalid\n", mu_msg);
> +
> +	mu_msg -= rpdev->base_vq_id;
> +
> +	/*
> +	 * Currently both PENDING_MSG and explicit-virtqueue-index
> +	 * messaging are supported.
> +	 * Whatever approach is taken, at this point 'mu_msg' contains
> +	 * the index of the vring which was just triggered.
> +	 */
> +	if (mu_msg < rpdev->num_of_vqs)
> +		vring_interrupt(mu_msg, rpdev->vq[mu_msg]);
> +
> +	return NOTIFY_DONE;
> +}
> +
> +static struct virtqueue *rp_find_vq(struct virtio_device *vdev,
> +				    unsigned index,
> +				    void (*callback)(struct virtqueue *vq),
> +				    const char *name)
> +{
> +	struct imx_rpmsg_vproc *rpdev = to_imx_rpdev(vdev);
> +	struct imx_rpmsg_vq_info *rpvq;
> +	struct virtqueue *vq;
> +	int err;
> +
> +	rpvq = kmalloc(sizeof(*rpvq), GFP_KERNEL);
> +	if (!rpvq)
> +		return ERR_PTR(-ENOMEM);
> +
> +	/* ioremap'ing normal memory, so we cast away sparse's complaints */
> +	rpvq->addr = (__force void *) ioremap_nocache(rpdev->vring[index],
> +							RPMSG_RING_SIZE);
> +	if (!rpvq->addr) {
> +		err = -ENOMEM;
> +		goto free_rpvq;
> +	}
> +
> +	memset(rpvq->addr, 0, RPMSG_RING_SIZE);
> +
> +	pr_debug("vring%d: phys 0x%x, virt 0x%x\n", index, rpdev->vring[index],
> +					(unsigned int) rpvq->addr);
> +
> +	vq = vring_new_virtqueue(index, RPMSG_NUM_BUFS / 2, RPMSG_VRING_ALIGN,
> +			vdev, true, rpvq->addr, imx_rpmsg_notify, callback,
> +			name);
> +	if (!vq) {
> +		pr_err("vring_new_virtqueue failed\n");
> +		err = -ENOMEM;
> +		goto unmap_vring;
> +	}
> +
> +	rpdev->vq[index] = vq;
> +	vq->priv = rpvq;
> +	/* system-wide unique id for this virtqueue */
> +	rpvq->vq_id = rpdev->base_vq_id + index;
> +	rpvq->rpdev = rpdev;
> +	mutex_init(&rpdev->lock);
> +
> +	return vq;
> +
> +unmap_vring:
> +	/* iounmap normal memory, so make sparse happy */
> +	iounmap((__force void __iomem *) rpvq->addr);
> +free_rpvq:
> +	kfree(rpvq);
> +	return ERR_PTR(err);
> +}
> +
> +static void imx_rpmsg_del_vqs(struct virtio_device *vdev) {
> +	struct virtqueue *vq, *n;
> +	struct imx_rpmsg_vproc *rpdev = to_imx_rpdev(vdev);
> +
> +	list_for_each_entry_safe(vq, n, &vdev->vqs, list) {
> +		struct imx_rpmsg_vq_info *rpvq = vq->priv;
> +
> +		iounmap(rpvq->addr);
> +		vring_del_virtqueue(vq);
> +		kfree(rpvq);
> +	}
> +
> +	if (&rpdev->nb)
> +		imx_mu_rpmsg_unregister_nb((const char *)rpdev->rproc_name,
> +				&rpdev->nb);
> +}
> +
> +static int imx_rpmsg_find_vqs(struct virtio_device *vdev, unsigned nvqs,
> +		       struct virtqueue *vqs[],
> +		       vq_callback_t *callbacks[],
> +		       const char *names[])
> +{
> +	struct imx_rpmsg_vproc *rpdev = to_imx_rpdev(vdev);
> +	int i, err;
> +
> +	/* we maintain two virtqueues per remote processor (for RX and TX) */
> +	if (nvqs != 2)
> +		return -EINVAL;
> +
> +	for (i = 0; i < nvqs; ++i) {
> +		vqs[i] = rp_find_vq(vdev, i, callbacks[i], names[i]);
> +		if (IS_ERR(vqs[i])) {
> +			err = PTR_ERR(vqs[i]);
> +			goto error;
> +		}
> +	}
> +
> +	rpdev->num_of_vqs = nvqs;
> +
> +	rpdev->nb.notifier_call = imx_mu_rpmsg_callback;
> +	imx_mu_rpmsg_register_nb((const char *)rpdev->rproc_name, 
> +&rpdev->nb);
> +
> +	return 0;
> +
> +error:
> +	imx_rpmsg_del_vqs(vdev);
> +	return err;
> +}
> +
> +static void imx_rpmsg_reset(struct virtio_device *vdev) {
> +	dev_dbg(&vdev->dev, "reset !\n");
> +}
> +
> +static u8 imx_rpmsg_get_status(struct virtio_device *vdev) {
> +	return 0;
> +}
> +
> +static void imx_rpmsg_set_status(struct virtio_device *vdev, u8 
> +status) {
> +	dev_dbg(&vdev->dev, "%s new status: %d\n", __func__, status); }
> +
> +static void imx_rpmsg_vproc_release(struct device *dev) {
> +	/* this handler is provided so driver core doesn't yell at us */ }
> +
> +static struct virtio_config_ops imx_rpmsg_config_ops = {
> +	.get_features	= imx_rpmsg_get_features,
> +	.finalize_features = imx_rpmsg_finalize_features,
> +	.find_vqs	= imx_rpmsg_find_vqs,
> +	.del_vqs	= imx_rpmsg_del_vqs,
> +	.reset		= imx_rpmsg_reset,
> +	.set_status	= imx_rpmsg_set_status,
> +	.get_status	= imx_rpmsg_get_status,
> +};
> +
> +static struct imx_rpmsg_vproc imx_rpmsg_vprocs[] = {
> +	{
> +		.vdev.id.device	= VIRTIO_ID_RPMSG,
> +		.vdev.config	= &imx_rpmsg_config_ops,
> +		.rproc_name	= "m4",
> +		.base_vq_id	= 0,
> +	},
> +};
> +
> +static const struct of_device_id imx_rpmsg_dt_ids[] = {
> +	{ .compatible = "fsl,imx6sx-rpmsg", },
> +	{ .compatible = "fsl,imx7d-rpmsg", },
> +	{ /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, imx_rpmsg_dt_ids);
> +
> +static int imx_rpmsg_probe(struct platform_device *pdev) {
> +	int i, ret = 0;
> +	struct device_node *np = pdev->dev.of_node;
> +
> +	for (i = 0; i < ARRAY_SIZE(imx_rpmsg_vprocs); i++) {
> +		struct imx_rpmsg_vproc *rpdev = &imx_rpmsg_vprocs[i];
> +
> +		if (!strcmp(rpdev->rproc_name, "m4")) {
> +			ret = of_device_is_compatible(np, "fsl,imx7d-rpmsg");
> +			ret |= of_device_is_compatible(np, "fsl,imx6sx-rpmsg");
> +			if (ret) {
> +				/* hardcodes here now. */
> +				rpdev->vring[0] = 0xBFFF0000;
> +				rpdev->vring[1] = 0xBFFF8000;
> +			}
> +		} else {
> +			break;
> +		}
> +
> +		pr_debug("%s rpdev%d: vring0 0x%x, vring1 0x%x\n", __func__,
> +				i, rpdev->vring[0], rpdev->vring[1]);
> +
> +		rpdev->vdev.dev.parent = &pdev->dev;
> +		rpdev->vdev.dev.release = imx_rpmsg_vproc_release;
> +
> +		ret = register_virtio_device(&rpdev->vdev);
> +		if (ret) {
> +			pr_err("%s failed to register rpdev: %d\n",
> +					__func__, ret);
> +			break;
> +		}
> +	}
> +
> +	return ret;
> +}
> +
> +static int imx_rpmsg_remove(struct platform_device *pdev) {
> +	int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(imx_rpmsg_vprocs); i++) {
> +		struct imx_rpmsg_vproc *rpdev = &imx_rpmsg_vprocs[i];
> +
> +		unregister_virtio_device(&rpdev->vdev);
> +	}
> +	return 0;
> +}
> +
> +static struct platform_driver imx_rpmsg_driver = {
> +	.driver = {
> +		   .owner = THIS_MODULE,
> +		   .name = "imx-rpmsg",
> +		   .of_match_table = imx_rpmsg_dt_ids,
> +		   },
> +	.probe = imx_rpmsg_probe,
> +	.remove = imx_rpmsg_remove,
> +};
> +
> +static int __init imx_rpmsg_init(void) {
> +	int ret;
> +
> +	ret = platform_driver_register(&imx_rpmsg_driver);
> +	if (ret)
> +		pr_err("Unable to initialize rpmsg driver\n");
> +	else
> +		pr_info("imx rpmsg driver is registered.\n");
> +
> +	return ret;
> +}
> +
> +static void __exit imx_rpmsg_exit(void) {
> +	pr_info("imx rpmsg driver is unregistered.\n");
> +	platform_driver_unregister(&imx_rpmsg_driver);
> +}
> +
> +module_exit(imx_rpmsg_exit);
> +module_init(imx_rpmsg_init);
> +
> +MODULE_AUTHOR("Freescale Semiconductor, Inc."); 
> +MODULE_DESCRIPTION("iMX remote processor messaging virtio device"); 
> +MODULE_LICENSE("GPL v2");
> diff --git a/arch/arm/mach-imx/mu.c b/arch/arm/mach-imx/mu.c new file 
> mode 100644 index 0000000..7b07f48
> --- /dev/null
> +++ b/arch/arm/mach-imx/mu.c
> @@ -0,0 +1,217 @@
> +/*
> + * Copyright (C) 2016 Freescale Semiconductor, Inc.
> + *
> + * The code contained herein is licensed under the GNU General Public
> + * License. You may obtain a copy of the GNU General Public License
> + * Version 2 or later at the following locations:
> + *
> + * http://www.opensource.org/licenses/gpl-license.html
> + * http://www.gnu.org/copyleft/gpl.html
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/delay.h>
> +#include <linux/init.h>
> +#include <linux/interrupt.h>
> +#include <linux/io.h>
> +#include <linux/irq.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +#include <linux/of_irq.h>
> +#include <linux/notifier.h>
> +#include <linux/platform_device.h>
> +#include "common.h"
> +#include "hardware.h"
> +
> +#define MU_ATR0_OFFSET	0x0
> +#define MU_ARR0_OFFSET	0x10
> +#define MU_ARR1_OFFSET	0x14
> +#define MU_ASR		0x20
> +#define MU_ACR		0x24
> +
> +#define MU_RPMSG_HANDSHAKE_INDEX	1
> +
> +struct imx_mu_rpmsg_box {
> +	const char *name;
> +	struct blocking_notifier_head notifier; };
> +
> +static struct imx_mu_rpmsg_box mu_rpmsg_box = {
> +	.name	= "m4",
> +};
> +
> +static void __iomem *mu_base;
> +static u32 m4_message;
> +static struct delayed_work rpmsg_work;
> +
> +static int imx_mu_send_message(unsigned int index, unsigned int data) 
> +{
> +	u32 val, ep;
> +	int i, te_flag = 0;
> +	unsigned long timeout = jiffies + msecs_to_jiffies(500);
> +
> +	/* wait for transfer buffer empty, and no event pending */
> +	do {
> +		val = readl_relaxed(mu_base + MU_ASR);
> +		ep = val & BIT(4);
> +		if (time_after(jiffies, timeout)) {
> +			pr_err("Waiting MU transmit buffer empty timeout!\n");
> +			return -EIO;
> +		}
> +	} while (((val & (1 << (20 + 3 - index))) == 0) || (ep == BIT(4)));
> +
> +	writel_relaxed(data, mu_base + index * 0x4 + MU_ATR0_OFFSET);
> +
> +	/*
> +	 * make a double check that TEn is not empty after write
> +	 */
> +	val = readl_relaxed(mu_base + MU_ASR);
> +	ep = val & BIT(4);
> +	if (((val & (1 << (20 + (3 - index)))) == 0) || (ep == BIT(4)))
> +		return 0;
> +
> +	/*
> +	 * Make sure that TEn flag is changed, after the ATRn is filled up.
> +	 */
> +	for (i = 0; i < 100; i++) {
> +		val = readl_relaxed(mu_base + MU_ASR);
> +		ep = val & BIT(4);
> +		if (((val & (1 << (20 + 3 - index))) == 0) || (ep == BIT(4))) {
> +			te_flag = 0;
> +			break;
> +		} else if (time_after(jiffies, timeout)) {
> +			/* Can't see TEn 1->0, maybe already handled! */
> +			te_flag = 1;
> +			break;
> +		}
> +	}
> +	if (te_flag == 0)
> +		pr_info("TEn isn't changed when ATRn is filled up.\n");
> +
> +	return 0;
> +}
> +
> +int imx_mu_rpmsg_send(unsigned int rpmsg) {
> +	return imx_mu_send_message(MU_RPMSG_HANDSHAKE_INDEX, rpmsg); }
> +
> +int imx_mu_rpmsg_register_nb(const char *name, struct notifier_block 
> +*nb) {
> +	if ((name == NULL) || (nb == NULL))
> +		return -EINVAL;
> +
> +	if (!strcmp(mu_rpmsg_box.name, name))
> +		blocking_notifier_chain_register(&(mu_rpmsg_box.notifier), nb);
> +	else
> +		return -ENOENT;
> +
> +	return 0;
> +}
> +
> +int imx_mu_rpmsg_unregister_nb(const char *name, struct 
> +notifier_block *nb) {
> +	if ((name == NULL) || (nb == NULL))
> +		return -EINVAL;
> +
> +	if (!strcmp(mu_rpmsg_box.name, name))
> +		blocking_notifier_chain_unregister(&(mu_rpmsg_box.notifier),
> +				nb);
> +	else
> +		return -ENOENT;
> +
> +	return 0;
> +}
> +
> +static void rpmsg_work_handler(struct work_struct *work) {
> +
> +	blocking_notifier_call_chain(&(mu_rpmsg_box.notifier), 4,
> +						(void *)m4_message);
> +	m4_message = 0;
> +}
> +
> +static irqreturn_t imx_mu_isr(int irq, void *param) {
> +	u32 irqs;
> +
> +	irqs = readl_relaxed(mu_base + MU_ASR);
> +
> +	/* RPMSG */
> +	if (irqs & (1 << 26)) {
> +		/* get message from receive buffer */
> +		m4_message = readl_relaxed(mu_base + MU_ARR1_OFFSET);
> +		schedule_delayed_work(&rpmsg_work, 0);
> +	}
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static int imx_mu_probe(struct platform_device *pdev) {
> +	int ret;
> +	u32 irq;
> +	struct device_node *np;
> +	struct clk *clk;
> +
> +	np = of_find_compatible_node(NULL, NULL, "fsl,imx6sx-mu");
> +	mu_base = of_iomap(np, 0);
> +	WARN_ON(!mu_base);
> +
> +	irq = platform_get_irq(pdev, 0);
> +	ret = request_irq(irq, imx_mu_isr,
> +		IRQF_EARLY_RESUME, "imx-mu", &mu_rpmsg_box);
> +	if (ret) {
> +		pr_err("%s: register interrupt %d failed, rc %d\n",
> +			__func__, irq, ret);
> +		return ret;
> +	}
> +
> +	ret = of_device_is_compatible(np, "fsl,imx7d-mu");
> +	if (ret) {
> +		clk = devm_clk_get(&pdev->dev, "mu");
> +		if (IS_ERR(clk)) {
> +			dev_err(&pdev->dev,
> +				"mu clock source missing or invalid\n");
> +			return PTR_ERR(clk);
> +		}
> +
> +		ret = clk_prepare_enable(clk);
> +		if (ret) {
> +			dev_err(&pdev->dev,
> +				"unable to enable mu clock\n");
> +			return ret;
> +		}
> +	}
> +
> +	INIT_DELAYED_WORK(&rpmsg_work, rpmsg_work_handler);
> +	/* enable the bit26(RIE1) of MU_ACR */
> +	writel_relaxed(readl_relaxed(mu_base + MU_ACR) | BIT(26),
> +			mu_base + MU_ACR);
> +	BLOCKING_INIT_NOTIFIER_HEAD(&(mu_rpmsg_box.notifier));
> +
> +	pr_info("MU is ready for cross core communication!\n");
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id imx_mu_ids[] = {
> +	{ .compatible = "fsl,imx6sx-mu" },
> +	{ .compatible = "fsl,imx7d-mu" },
> +	{ }
> +};
> +
> +static struct platform_driver imx_mu_driver = {
> +	.driver = {
> +		.name   = "imx-mu",
> +		.owner  = THIS_MODULE,
> +		.of_match_table = imx_mu_ids,
> +	},
> +	.probe = imx_mu_probe,
> +};
> +
> +static int __init imx_mu_init(void)
> +{
> +	return platform_driver_register(&imx_mu_driver);
> +}
> +subsys_initcall(imx_mu_init);
> diff --git a/include/linux/imx_rpmsg.h b/include/linux/imx_rpmsg.h new 
> file mode 100644 index 0000000..2b0dca5
> --- /dev/null
> +++ b/include/linux/imx_rpmsg.h
> @@ -0,0 +1,27 @@
> +/*
> + * Copyright (C) 2016 Freescale Semiconductor, Inc.
> + */
> +
> +/*
> + * The code contained herein is licensed under the GNU Lesser General
> + * Public License.  You may obtain a copy of the GNU Lesser General
> + * Public License Version 2.1 or later at the following locations:
> + *
> + * http://www.opensource.org/licenses/lgpl-license.html
> + * http://www.gnu.org/copyleft/lgpl.html
> + */
> +
> +/*
> + * @file linux/imx_rpmsg.h
> + *
> + * @brief Global header file for imx RPMSG
> + *
> + * @ingroup RPMSG
> + */
> +#ifndef __LINUX_IMX_RPMSG_H__
> +#define __LINUX_IMX_RPMSG_H__
> +
> +int imx_mu_rpmsg_send(unsigned int vq_id); int 
> +imx_mu_rpmsg_register_nb(const char *name, struct notifier_block 
> +*nb); int imx_mu_rpmsg_unregister_nb(const char *name, struct 
> +notifier_block *nb); #endif /* __LINUX_IMX_RPMSG_H__ */
> --
> 1.9.1
> 
>