[4/4] drivers/mailbox: Add ASpeed mailbox driver
diff mbox

Message ID 20170112002910.3650-5-cyrilbur@gmail.com
State Awaiting Upstream
Headers show

Commit Message

Cyril Bur Jan. 12, 2017, 12:29 a.m. UTC
This provides access to the mbox registers on the ast2400 and ast2500
boards.

This driver allows arbitrary reads and writes to the 16 data registers as
the other end may have configured the mbox hardware to provide an
interrupt when a specific register gets written to.

Signed-off-by: Cyril Bur <cyrilbur@gmail.com>
---
 drivers/mailbox/Kconfig       |   9 ++
 drivers/mailbox/Makefile      |   2 +
 drivers/mailbox/aspeed-mbox.c | 334 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 345 insertions(+)
 create mode 100644 drivers/mailbox/aspeed-mbox.c

Comments

Joel Stanley Feb. 7, 2017, 5:40 a.m. UTC | #1
On Thu, Jan 12, 2017 at 10:59 AM, Cyril Bur <cyrilbur@gmail.com> wrote:
> This provides access to the mbox registers on the ast2400 and ast2500
> boards.

s/boards/SoCs/

>
> This driver allows arbitrary reads and writes to the 16 data registers as
> the other end may have configured the mbox hardware to provide an
> interrupt when a specific register gets written to.
>
> Signed-off-by: Cyril Bur <cyrilbur@gmail.com>

Send this to lkml as well next time you submit.

> ---
>  drivers/mailbox/Kconfig       |   9 ++
>  drivers/mailbox/Makefile      |   2 +
>  drivers/mailbox/aspeed-mbox.c | 334 ++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 345 insertions(+)
>  create mode 100644 drivers/mailbox/aspeed-mbox.c
>
> diff --git a/drivers/mailbox/Kconfig b/drivers/mailbox/Kconfig
> index ceff415f201c..10a7f3f2765c 100644
> --- a/drivers/mailbox/Kconfig
> +++ b/drivers/mailbox/Kconfig
> @@ -152,4 +152,13 @@ config BCM_PDC_MBOX
>           Mailbox implementation for the Broadcom PDC ring manager,
>           which provides access to various offload engines on Broadcom
>           SoCs. Say Y here if you want to use the Broadcom PDC.
> +
> +config ASPEED_MBOX

Call this ASPEED_LPC_MAILBOX, as it's a in the LPC IP block.

> +       depends on (ARCH_ASPEED || COMPILE_TEST) && REGMAP && MFD_SYSCON
> +       bool "Aspeed ast2400/2500 Mailbox Controller"

Call this Aspeed LPC Mailbox Controller, as the layout is shared by
SoCs other than the 2500 and 2400.

> +       default "y"
> +       ---help---
> +         Provides a driver for the MBOX registers found on Aspeed SOCs
> +         (AST2400 and AST2500). This driver provides a device for aspeed
> +         mbox registers
>  endif
> diff --git a/drivers/mailbox/Makefile b/drivers/mailbox/Makefile
> index 7dde4f609ae8..db5b4f3f29e0 100644
> --- a/drivers/mailbox/Makefile
> +++ b/drivers/mailbox/Makefile
> @@ -31,3 +31,5 @@ obj-$(CONFIG_HI6220_MBOX)     += hi6220-mailbox.o
>  obj-$(CONFIG_BCM_PDC_MBOX)     += bcm-pdc-mailbox.o
>
>  obj-$(CONFIG_TEGRA_HSP_MBOX)   += tegra-hsp.o
> +
> +obj-$(CONFIG_ASPEED_MBOX)      += aspeed-mbox.o
> diff --git a/drivers/mailbox/aspeed-mbox.c b/drivers/mailbox/aspeed-mbox.c
> new file mode 100644
> index 000000000000..c4ee6ba228ea
> --- /dev/null
> +++ b/drivers/mailbox/aspeed-mbox.c

> +
> +static ssize_t aspeed_mbox_read(struct file *file, char __user *buf,
> +                               size_t count, loff_t *ppos)
> +{
> +       struct aspeed_mbox *mbox = file_mbox(file);
> +       char __user *p = buf;
> +       ssize_t ret;
> +       int i;
> +
> +       if (!access_ok(VERIFY_WRITE, buf, count))
> +               return -EFAULT;

As discussed in the LPC driver review:

 "And don't call access_ok(), it's racy and no driver should ever do that."

Make sure all of the things you fixed in that driver are fixed in this one.

> +
> +       if (count + *ppos > ASPEED_MBOX_NUM_REGS)
> +               return -EINVAL;
> +
> +       if (file->f_flags & O_NONBLOCK) {
> +               if (!(aspeed_mbox_inb(mbox, ASPEED_MBOX_BMC_CTRL) &
> +                               ASPEED_MBOX_CTRL_RECV))
> +                       return -EAGAIN;
> +       } else if (wait_event_interruptible(mbox->queue,
> +                               aspeed_mbox_inb(mbox, ASPEED_MBOX_BMC_CTRL) &
> +                               ASPEED_MBOX_CTRL_RECV)) {
> +               return -ERESTARTSYS;
> +       }
> +
> +       mutex_lock(&mbox->mutex);
> +
> +       for (i = *ppos; count > 0 && i < ASPEED_MBOX_NUM_REGS; i++) {
> +               uint8_t reg = aspeed_mbox_inb(mbox, ASPEED_MBOX_DATA_0 + (i * 4));
> +
> +               ret = __put_user(reg, p);
> +               if (ret)
> +                       goto out_unlock;
> +
> +               p++;
> +               count--;
> +       }
> +
> +       /* ASPEED_MBOX_CTRL_RECV bit is W1C, this also unmasks in 1 step */

W1C? Write to clear?

> +       aspeed_mbox_outb(mbox, ASPEED_MBOX_CTRL_RECV, ASPEED_MBOX_BMC_CTRL);
> +       ret = p - buf;
> +
> +out_unlock:
> +       mutex_unlock(&mbox->mutex);
> +       return ret;
> +}
> +

> +module_platform_driver(aspeed_mbox_driver);
> +
> +MODULE_DEVICE_TABLE(of, aspeed_mbox_match);
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Cyril Bur <cyrilbur@gmail.com>");
> +MODULE_DESCRIPTION("ASpeed mailbox device driver");

ASPEED or Aspeed.

> --
> 2.11.0
>
Benjamin Herrenschmidt Feb. 7, 2017, 5:44 a.m. UTC | #2
On Tue, 2017-02-07 at 16:10 +1030, Joel Stanley wrote:

> > +static ssize_t aspeed_mbox_read(struct file *file, char __user *buf,
> > +                               size_t count, loff_t *ppos)
> > +{
> > +       struct aspeed_mbox *mbox = file_mbox(file);
> > +       char __user *p = buf;
> > +       ssize_t ret;
> > +       int i;
> > +
> > +       if (!access_ok(VERIFY_WRITE, buf, count))
> > +               return -EFAULT;
> 
> As discussed in the LPC driver review:
> 
>  "And don't call access_ok(), it's racy and no driver should ever do that."
> 
> Make sure all of the things you fixed in that driver are fixed in this one.

Well... I don't entirely agree with Greg on that one :-) In this specific
case, since he's using __put_user() below, he must use access_ok() first.

The "alternate" option is to bounce everything via a local memory array,
copy_to/from_user (to/from that array) and then do the loop of inb/outb,
but in the grand scheme of things, what is written here is correct *and*
more efficient than the alternate approach. On such a slow SoC, those
cycles do count.

> > +
> > +       if (count + *ppos > ASPEED_MBOX_NUM_REGS)
> > +               return -EINVAL;
> > +
> > +       if (file->f_flags & O_NONBLOCK) {
> > +               if (!(aspeed_mbox_inb(mbox, ASPEED_MBOX_BMC_CTRL) &
> > +                               ASPEED_MBOX_CTRL_RECV))
> > +                       return -EAGAIN;
> > +       } else if (wait_event_interruptible(mbox->queue,
> > +                               aspeed_mbox_inb(mbox, ASPEED_MBOX_BMC_CTRL) &
> > +                               ASPEED_MBOX_CTRL_RECV)) {
> > +               return -ERESTARTSYS;
> > +       }
> > +
> > +       mutex_lock(&mbox->mutex);
> > +
> > +       for (i = *ppos; count > 0 && i < ASPEED_MBOX_NUM_REGS; i++) {
> > +               uint8_t reg = aspeed_mbox_inb(mbox, ASPEED_MBOX_DATA_0 + (i * 4));
> > +
> > +               ret = __put_user(reg, p);
> > +               if (ret)
> > +                       goto out_unlock;
> > +
> > +               p++;
> > +               count--;
> > +       }
> > +
> > +       /* ASPEED_MBOX_CTRL_RECV bit is W1C, this also unmasks in 1 step */
> 
> W1C? Write to clear?
> 
> > +       aspeed_mbox_outb(mbox, ASPEED_MBOX_CTRL_RECV, ASPEED_MBOX_BMC_CTRL);
> > +       ret = p - buf;
> > +
> > +out_unlock:
> > +       mutex_unlock(&mbox->mutex);
> > +       return ret;
> > +}
> > +
> > +module_platform_driver(aspeed_mbox_driver);
> > +
> > +MODULE_DEVICE_TABLE(of, aspeed_mbox_match);
> > +MODULE_LICENSE("GPL");
> > > > +MODULE_AUTHOR("Cyril Bur <cyrilbur@gmail.com>");
> > +MODULE_DESCRIPTION("ASpeed mailbox device driver");
> 
> ASPEED or Aspeed.
> 
> > --
> > 2.11.0
> >
Cyril Bur Feb. 7, 2017, 10:57 p.m. UTC | #3
On Tue, 2017-02-07 at 16:10 +1030, Joel Stanley wrote:
> On Thu, Jan 12, 2017 at 10:59 AM, Cyril Bur <cyrilbur@gmail.com> wrote:
> > This provides access to the mbox registers on the ast2400 and ast2500
> > boards.
> 

Hey Joel,

Thanks for review, just one thing, I'll fixup the rest.

Cyril

> s/boards/SoCs/
> 
> > 
> > This driver allows arbitrary reads and writes to the 16 data registers as
> > the other end may have configured the mbox hardware to provide an
> > interrupt when a specific register gets written to.
> > 
> > Signed-off-by: Cyril Bur <cyrilbur@gmail.com>
> 
> Send this to lkml as well next time you submit.
> 
> > ---
> >  drivers/mailbox/Kconfig       |   9 ++
> >  drivers/mailbox/Makefile      |   2 +
> >  drivers/mailbox/aspeed-mbox.c | 334 ++++++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 345 insertions(+)
> >  create mode 100644 drivers/mailbox/aspeed-mbox.c
> > 
> > diff --git a/drivers/mailbox/Kconfig b/drivers/mailbox/Kconfig
> > index ceff415f201c..10a7f3f2765c 100644
> > --- a/drivers/mailbox/Kconfig
> > +++ b/drivers/mailbox/Kconfig
> > @@ -152,4 +152,13 @@ config BCM_PDC_MBOX
> >           Mailbox implementation for the Broadcom PDC ring manager,
> >           which provides access to various offload engines on Broadcom
> >           SoCs. Say Y here if you want to use the Broadcom PDC.
> > +
> > +config ASPEED_MBOX
> 
> Call this ASPEED_LPC_MAILBOX, as it's a in the LPC IP block.
> 

I think I'll stick with ASPEED_LPC_MBOX, the rest of the file uses MBOX
more widely when talking about controllers.

> > +       depends on (ARCH_ASPEED || COMPILE_TEST) && REGMAP && MFD_SYSCON
> > +       bool "Aspeed ast2400/2500 Mailbox Controller"
> 
> Call this Aspeed LPC Mailbox Controller, as the layout is shared by
> SoCs other than the 2500 and 2400.
> 
> > +       default "y"
> > +       ---help---
> > +         Provides a driver for the MBOX registers found on Aspeed SOCs
> > +         (AST2400 and AST2500). This driver provides a device for aspeed
> > +         mbox registers
> >  endif
> > diff --git a/drivers/mailbox/Makefile b/drivers/mailbox/Makefile
> > index 7dde4f609ae8..db5b4f3f29e0 100644
> > --- a/drivers/mailbox/Makefile
> > +++ b/drivers/mailbox/Makefile
> > @@ -31,3 +31,5 @@ obj-$(CONFIG_HI6220_MBOX)     += hi6220-mailbox.o
> >  obj-$(CONFIG_BCM_PDC_MBOX)     += bcm-pdc-mailbox.o
> > 
> >  obj-$(CONFIG_TEGRA_HSP_MBOX)   += tegra-hsp.o
> > +
> > +obj-$(CONFIG_ASPEED_MBOX)      += aspeed-mbox.o
> > diff --git a/drivers/mailbox/aspeed-mbox.c b/drivers/mailbox/aspeed-mbox.c
> > new file mode 100644
> > index 000000000000..c4ee6ba228ea
> > --- /dev/null
> > +++ b/drivers/mailbox/aspeed-mbox.c
> > +
> > +static ssize_t aspeed_mbox_read(struct file *file, char __user *buf,
> > +                               size_t count, loff_t *ppos)
> > +{
> > +       struct aspeed_mbox *mbox = file_mbox(file);
> > +       char __user *p = buf;
> > +       ssize_t ret;
> > +       int i;
> > +
> > +       if (!access_ok(VERIFY_WRITE, buf, count))
> > +               return -EFAULT;
> 
> As discussed in the LPC driver review:
> 
>  "And don't call access_ok(), it's racy and no driver should ever do that."
> 
> Make sure all of the things you fixed in that driver are fixed in this one.
> 
> > +
> > +       if (count + *ppos > ASPEED_MBOX_NUM_REGS)
> > +               return -EINVAL;
> > +
> > +       if (file->f_flags & O_NONBLOCK) {
> > +               if (!(aspeed_mbox_inb(mbox, ASPEED_MBOX_BMC_CTRL) &
> > +                               ASPEED_MBOX_CTRL_RECV))
> > +                       return -EAGAIN;
> > +       } else if (wait_event_interruptible(mbox->queue,
> > +                               aspeed_mbox_inb(mbox, ASPEED_MBOX_BMC_CTRL) &
> > +                               ASPEED_MBOX_CTRL_RECV)) {
> > +               return -ERESTARTSYS;
> > +       }
> > +
> > +       mutex_lock(&mbox->mutex);
> > +
> > +       for (i = *ppos; count > 0 && i < ASPEED_MBOX_NUM_REGS; i++) {
> > +               uint8_t reg = aspeed_mbox_inb(mbox, ASPEED_MBOX_DATA_0 + (i * 4));
> > +
> > +               ret = __put_user(reg, p);
> > +               if (ret)
> > +                       goto out_unlock;
> > +
> > +               p++;
> > +               count--;
> > +       }
> > +
> > +       /* ASPEED_MBOX_CTRL_RECV bit is W1C, this also unmasks in 1 step */
> 
> W1C? Write to clear?
> 
> > +       aspeed_mbox_outb(mbox, ASPEED_MBOX_CTRL_RECV, ASPEED_MBOX_BMC_CTRL);
> > +       ret = p - buf;
> > +
> > +out_unlock:
> > +       mutex_unlock(&mbox->mutex);
> > +       return ret;
> > +}
> > +
> > +module_platform_driver(aspeed_mbox_driver);
> > +
> > +MODULE_DEVICE_TABLE(of, aspeed_mbox_match);
> > +MODULE_LICENSE("GPL");
> > +MODULE_AUTHOR("Cyril Bur <cyrilbur@gmail.com>");
> > +MODULE_DESCRIPTION("ASpeed mailbox device driver");
> 
> ASPEED or Aspeed.
> 
> > --
> > 2.11.0
> >
Joel Stanley Feb. 7, 2017, 10:59 p.m. UTC | #4
On Wed, Feb 8, 2017 at 9:27 AM, Cyril Bur <cyrilbur@gmail.com> wrote:
>> > diff --git a/drivers/mailbox/Kconfig b/drivers/mailbox/Kconfig
>> > index ceff415f201c..10a7f3f2765c 100644
>> > --- a/drivers/mailbox/Kconfig
>> > +++ b/drivers/mailbox/Kconfig
>> > @@ -152,4 +152,13 @@ config BCM_PDC_MBOX
>> >           Mailbox implementation for the Broadcom PDC ring manager,
>> >           which provides access to various offload engines on Broadcom
>> >           SoCs. Say Y here if you want to use the Broadcom PDC.
>> > +
>> > +config ASPEED_MBOX
>>
>> Call this ASPEED_LPC_MAILBOX, as it's a in the LPC IP block.
>>
>
> I think I'll stick with ASPEED_LPC_MBOX, the rest of the file uses MBOX
> more widely when talking about controllers.

No worries. I just wanted the _LPC bit added.

Cheers,

Joel

Patch
diff mbox

diff --git a/drivers/mailbox/Kconfig b/drivers/mailbox/Kconfig
index ceff415f201c..10a7f3f2765c 100644
--- a/drivers/mailbox/Kconfig
+++ b/drivers/mailbox/Kconfig
@@ -152,4 +152,13 @@  config BCM_PDC_MBOX
 	  Mailbox implementation for the Broadcom PDC ring manager,
 	  which provides access to various offload engines on Broadcom
 	  SoCs. Say Y here if you want to use the Broadcom PDC.
+
+config ASPEED_MBOX
+	depends on (ARCH_ASPEED || COMPILE_TEST) && REGMAP && MFD_SYSCON
+	bool "Aspeed ast2400/2500 Mailbox Controller"
+	default "y"
+	---help---
+	  Provides a driver for the MBOX registers found on Aspeed SOCs
+	  (AST2400 and AST2500). This driver provides a device for aspeed
+	  mbox registers
 endif
diff --git a/drivers/mailbox/Makefile b/drivers/mailbox/Makefile
index 7dde4f609ae8..db5b4f3f29e0 100644
--- a/drivers/mailbox/Makefile
+++ b/drivers/mailbox/Makefile
@@ -31,3 +31,5 @@  obj-$(CONFIG_HI6220_MBOX)	+= hi6220-mailbox.o
 obj-$(CONFIG_BCM_PDC_MBOX)	+= bcm-pdc-mailbox.o
 
 obj-$(CONFIG_TEGRA_HSP_MBOX)	+= tegra-hsp.o
+
+obj-$(CONFIG_ASPEED_MBOX)	+= aspeed-mbox.o
diff --git a/drivers/mailbox/aspeed-mbox.c b/drivers/mailbox/aspeed-mbox.c
new file mode 100644
index 000000000000..c4ee6ba228ea
--- /dev/null
+++ b/drivers/mailbox/aspeed-mbox.c
@@ -0,0 +1,334 @@ 
+/*
+ * Copyright 2016 IBM Corporation
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/interrupt.h>
+#include <linux/mfd/syscon.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/of_irq.h>
+#include <linux/platform_device.h>
+#include <linux/poll.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+
+#define DEVICE_NAME	"aspeed-mbox"
+
+#define ASPEED_MBOX_NUM_REGS 16
+
+#define ASPEED_MBOX_DATA_0 0x00
+#define ASPEED_MBOX_STATUS_0 0x40
+#define ASPEED_MBOX_STATUS_1 0x44
+#define ASPEED_MBOX_BMC_CTRL 0x48
+#define   ASPEED_MBOX_CTRL_RECV BIT(7)
+#define   ASPEED_MBOX_CTRL_MASK BIT(1)
+#define   ASPEED_MBOX_CTRL_SEND BIT(0)
+#define ASPEED_MBOX_HOST_CTRL 0x4c
+#define ASPEED_MBOX_INTERRUPT_0 0x50
+#define ASPEED_MBOX_INTERRUPT_1 0x54
+
+struct aspeed_mbox {
+	struct miscdevice	miscdev;
+	struct regmap		*regmap;
+	unsigned int		base;
+	wait_queue_head_t	queue;
+	struct mutex		mutex;
+};
+
+static atomic_t aspeed_mbox_open_count = ATOMIC_INIT(0);
+
+static u8 aspeed_mbox_inb(struct aspeed_mbox *mbox, int reg)
+{
+	/*
+	 * The mbox registers are actually only one byte but are addressed
+	 * four bytes apart. The other three bytes are marked 'reserved',
+	 * they *should* be zero but lets not rely on it.
+	 * I am going to rely on the fact we can casually read/write to them...
+	 */
+	unsigned int val = 0xff; /* If regmap throws an error return 0xff */
+	int rc = regmap_read(mbox->regmap, mbox->base + reg, &val);
+
+	if (rc)
+		dev_err(mbox->miscdev.parent, "regmap_read() failed with "
+				"%d (reg: 0x%08x)\n", rc, reg);
+
+	return val & 0xff;
+}
+
+static void aspeed_mbox_outb(struct aspeed_mbox *mbox, u8 data, int reg)
+{
+	int rc = regmap_write(mbox->regmap, mbox->base + reg, data);
+
+	if (rc)
+		dev_err(mbox->miscdev.parent, "regmap_write() failed with "
+				"%d (data: %u reg: 0x%08x)\n", rc, data, reg);
+}
+
+static struct aspeed_mbox *file_mbox(struct file *file)
+{
+	return container_of(file->private_data, struct aspeed_mbox, miscdev);
+}
+
+static int aspeed_mbox_open(struct inode *inode, struct file *file)
+{
+	struct aspeed_mbox *mbox = file_mbox(file);
+
+	if (atomic_inc_return(&aspeed_mbox_open_count) == 1) {
+		/*
+		 * Clear the interrupt status bit if it was left on and unmask
+		 * interrupts.
+		 * ASPEED_MBOX_CTRL_RECV bit is W1C, this also unmasks in 1 step
+		 */
+		aspeed_mbox_outb(mbox, ASPEED_MBOX_CTRL_RECV, ASPEED_MBOX_BMC_CTRL);
+		return 0;
+	}
+
+	atomic_dec(&aspeed_mbox_open_count);
+	return -EBUSY;
+}
+
+static ssize_t aspeed_mbox_read(struct file *file, char __user *buf,
+				size_t count, loff_t *ppos)
+{
+	struct aspeed_mbox *mbox = file_mbox(file);
+	char __user *p = buf;
+	ssize_t ret;
+	int i;
+
+	if (!access_ok(VERIFY_WRITE, buf, count))
+		return -EFAULT;
+
+	if (count + *ppos > ASPEED_MBOX_NUM_REGS)
+		return -EINVAL;
+
+	if (file->f_flags & O_NONBLOCK) {
+		if (!(aspeed_mbox_inb(mbox, ASPEED_MBOX_BMC_CTRL) &
+				ASPEED_MBOX_CTRL_RECV))
+			return -EAGAIN;
+	} else if (wait_event_interruptible(mbox->queue,
+				aspeed_mbox_inb(mbox, ASPEED_MBOX_BMC_CTRL) &
+				ASPEED_MBOX_CTRL_RECV)) {
+		return -ERESTARTSYS;
+	}
+
+	mutex_lock(&mbox->mutex);
+
+	for (i = *ppos; count > 0 && i < ASPEED_MBOX_NUM_REGS; i++) {
+		uint8_t reg = aspeed_mbox_inb(mbox, ASPEED_MBOX_DATA_0 + (i * 4));
+
+		ret = __put_user(reg, p);
+		if (ret)
+			goto out_unlock;
+
+		p++;
+		count--;
+	}
+
+	/* ASPEED_MBOX_CTRL_RECV bit is W1C, this also unmasks in 1 step */
+	aspeed_mbox_outb(mbox, ASPEED_MBOX_CTRL_RECV, ASPEED_MBOX_BMC_CTRL);
+	ret = p - buf;
+
+out_unlock:
+	mutex_unlock(&mbox->mutex);
+	return ret;
+}
+
+static ssize_t aspeed_mbox_write(struct file *file, const char __user *buf,
+				size_t count, loff_t *ppos)
+{
+	struct aspeed_mbox *mbox = file_mbox(file);
+	const char __user *p = buf;
+	ssize_t ret;
+	char c;
+	int i;
+
+	if (!access_ok(VERIFY_READ, buf, count))
+		return -EFAULT;
+
+	if (count + *ppos > ASPEED_MBOX_NUM_REGS)
+		return -EINVAL;
+
+	mutex_lock(&mbox->mutex);
+
+	for (i = *ppos; count > 0 && i < ASPEED_MBOX_NUM_REGS; i++) {
+		ret = __get_user(c, p);
+		if (ret)
+			goto out_unlock;
+
+		aspeed_mbox_outb(mbox, c, ASPEED_MBOX_DATA_0 + (i * 4));
+		p++;
+		count--;
+	}
+
+	aspeed_mbox_outb(mbox, ASPEED_MBOX_CTRL_SEND, ASPEED_MBOX_BMC_CTRL);
+	ret = p - buf;
+
+out_unlock:
+	mutex_unlock(&mbox->mutex);
+	return ret;
+}
+
+static unsigned int aspeed_mbox_poll(struct file *file, poll_table *wait)
+{
+	struct aspeed_mbox *mbox = file_mbox(file);
+	unsigned int mask = 0;
+
+	poll_wait(file, &mbox->queue, wait);
+
+	if (aspeed_mbox_inb(mbox, ASPEED_MBOX_BMC_CTRL) & ASPEED_MBOX_CTRL_RECV)
+		mask |= POLLIN;
+
+	return mask;
+}
+
+static int aspeed_mbox_release(struct inode *inode, struct file *file)
+{
+	atomic_dec(&aspeed_mbox_open_count);
+	return 0;
+}
+
+static const struct file_operations aspeed_mbox_fops = {
+	.owner		= THIS_MODULE,
+	.llseek		= no_seek_end_llseek,
+	.read		= aspeed_mbox_read,
+	.write		= aspeed_mbox_write,
+	.open		= aspeed_mbox_open,
+	.release	= aspeed_mbox_release,
+	.poll		= aspeed_mbox_poll,
+};
+
+static irqreturn_t aspeed_mbox_irq(int irq, void *arg)
+{
+	struct aspeed_mbox *mbox = arg;
+
+	if (!(aspeed_mbox_inb(mbox, ASPEED_MBOX_BMC_CTRL) & ASPEED_MBOX_CTRL_RECV))
+		return IRQ_NONE;
+
+	/*
+	 * Leave the status bit set so that we know the data is for us,
+	 * clear it once it has been read.
+	 */
+
+	/* Mask it off, we'll clear it when we the data gets read */
+	aspeed_mbox_outb(mbox, ASPEED_MBOX_CTRL_MASK, ASPEED_MBOX_BMC_CTRL);
+
+	wake_up(&mbox->queue);
+	return IRQ_HANDLED;
+}
+
+static int aspeed_mbox_config_irq(struct aspeed_mbox *mbox,
+		struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	int rc, irq;
+
+	irq = irq_of_parse_and_map(dev->of_node, 0);
+	if (!irq)
+		return -ENODEV;
+
+	rc = devm_request_irq(dev, irq, aspeed_mbox_irq,
+			IRQF_SHARED, DEVICE_NAME, mbox);
+	if (rc < 0) {
+		dev_err(dev, "Unable to request IRQ %d\n", irq);
+		return rc;
+	}
+
+	/*
+	 * Disable all register based interrupts.
+	 */
+	aspeed_mbox_outb(mbox, 0x00, ASPEED_MBOX_INTERRUPT_0); /* regs 0 - 7 */
+	aspeed_mbox_outb(mbox, 0x00, ASPEED_MBOX_INTERRUPT_1); /* regs 8 - 15 */
+
+	/* These registers are write one to clear. Clear them. */
+	aspeed_mbox_outb(mbox, 0xff, ASPEED_MBOX_STATUS_0);
+	aspeed_mbox_outb(mbox, 0xff, ASPEED_MBOX_STATUS_1);
+
+	aspeed_mbox_outb(mbox, ASPEED_MBOX_CTRL_RECV, ASPEED_MBOX_BMC_CTRL);
+	return 0;
+}
+
+static int aspeed_mbox_probe(struct platform_device *pdev)
+{
+	struct aspeed_mbox *mbox;
+	struct device *dev;
+	int rc;
+
+	dev = &pdev->dev;
+
+	mbox = devm_kzalloc(dev, sizeof(*mbox), GFP_KERNEL);
+	if (!mbox)
+		return -ENOMEM;
+
+	dev_set_drvdata(&pdev->dev, mbox);
+
+	rc = of_property_read_u32(dev->of_node, "reg", &mbox->base);
+	if (rc) {
+		dev_err(dev, "Couldn't read reg device-tree property\n");
+		return rc;
+	}
+
+	mbox->regmap = syscon_node_to_regmap(
+			pdev->dev.parent->of_node);
+	if (IS_ERR(mbox->regmap)) {
+		dev_err(dev, "Couldn't get regmap\n");
+		return -ENODEV;
+	}
+
+	mutex_init(&mbox->mutex);
+	init_waitqueue_head(&mbox->queue);
+
+	mbox->miscdev.minor = MISC_DYNAMIC_MINOR;
+	mbox->miscdev.name = DEVICE_NAME;
+	mbox->miscdev.fops = &aspeed_mbox_fops;
+	mbox->miscdev.parent = dev;
+	rc = misc_register(&mbox->miscdev);
+	if (rc) {
+		dev_err(dev, "Unable to register device\n");
+		return rc;
+	}
+
+	rc = aspeed_mbox_config_irq(mbox, pdev);
+	if (rc) {
+		dev_err(dev, "Failed to configure IRQ\n");
+		misc_deregister(&mbox->miscdev);
+		return rc;
+	}
+
+	return 0;
+}
+
+static int aspeed_mbox_remove(struct platform_device *pdev)
+{
+	struct aspeed_mbox *mbox = dev_get_drvdata(&pdev->dev);
+
+	misc_deregister(&mbox->miscdev);
+
+	return 0;
+}
+
+static const struct of_device_id aspeed_mbox_match[] = {
+	{ .compatible = "aspeed,ast2400-mbox" },
+	{ .compatible = "aspeed,ast2500-mbox" },
+	{ },
+};
+
+static struct platform_driver aspeed_mbox_driver = {
+	.driver = {
+		.name		= DEVICE_NAME,
+		.of_match_table = aspeed_mbox_match,
+	},
+	.probe = aspeed_mbox_probe,
+	.remove = aspeed_mbox_remove,
+};
+
+module_platform_driver(aspeed_mbox_driver);
+
+MODULE_DEVICE_TABLE(of, aspeed_mbox_match);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Cyril Bur <cyrilbur@gmail.com>");
+MODULE_DESCRIPTION("ASpeed mailbox device driver");