misc: Add ASPEED mbox driver

This provides access to the mbox registers on the ast2400 and ast2500
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.

OpenBMC-Staging-Count: 6
[joel: move to drivers/misc as this isn't a mailbox driver]
Signed-off-by: Cyril Bur <cyrilbur@gmail.com>
Signed-off-by: Joel Stanley <joel@jms.id.au>

3 files changed, 342 insertions, 0 deletions

diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index f417b06e11c5..ad9fb2edf172 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -501,6 +501,13 @@ config ASPEED_LPC_SNOOP
 	  allows the BMC to listen on and save the data written by
 	  the host to an arbitrary LPC I/O port.
 
+config ASPEED_LPC_MBOX
+	tristate "Aspeed LPC Mailbox Controller"
+	depends on (ARCH_ASPEED || COMPILE_TEST) && REGMAP && MFD_SYSCON
+	---help---
+	  Expose the ASPEED LPC MBOX registers found on Aspeed SOCs (AST2400
+	  and AST2500) to userspace.
+
 config PCI_ENDPOINT_TEST
 	depends on PCI
 	select CRC32
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index e39ccbbc1b3a..3782b8ad0dc6 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -55,6 +55,7 @@ obj-$(CONFIG_VEXPRESS_SYSCFG)	+= vexpress-syscfg.o
 obj-$(CONFIG_CXL_BASE)		+= cxl/
 obj-$(CONFIG_ASPEED_LPC_CTRL)	+= aspeed-lpc-ctrl.o
 obj-$(CONFIG_ASPEED_LPC_SNOOP)	+= aspeed-lpc-snoop.o
+obj-$(CONFIG_ASPEED_LPC_MBOX)	+= aspeed-lpc-mbox.o
 obj-$(CONFIG_PCI_ENDPOINT_TEST)	+= pci_endpoint_test.o
 obj-$(CONFIG_OCXL)		+= ocxl/
 obj-y				+= cardreader/
diff --git a/drivers/misc/aspeed-lpc-mbox.c b/drivers/misc/aspeed-lpc-mbox.c
new file mode 100644
index 000000000000..bab86e5e2943
--- /dev/null
+++ b/drivers/misc/aspeed-lpc-mbox.c
@@ -0,0 +1,334 @@
+/*
+ * Copyright 2017 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(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 write to clear, 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(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");