mailbox: Enable BCM2835 mailbox support

This mailbox driver provides a single mailbox channel to write 32-bit
values to the VPU and get a 32-bit response.  The Raspberry Pi
firmware uses this mailbox channel to implement firmware calls, while
Roku 2 (despite being derived from the same firmware tree) doesn't.

The driver was originally submitted by Lubomir, based on the
out-of-tree 2708 mailbox driver.  Eric Anholt fixed it up for
upstreaming, with the major functional change being that it now has no
notion of multiple channels (since that is a firmware-dependent
concept) and instead the raspberrypi-firmware driver will do that
bit-twiddling in its own messages.
[Jassi: made the 'mbox_chan_ops' struct as const and removed a redundant
variable]

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Signed-off-by: Craig McGeachie <slapdau@yahoo.com.au>
Signed-off-by: Eric Anholt <eric@anholt.net>
Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>

drivers/mailbox/Kconfig

@@ -61,4 +61,13 @@ config ALTERA_MBOX
 	  An implementation of the Altera Mailbox soft core. It is used
 	  to send message between processors. Say Y here if you want to use the
 	  Altera mailbox support.
+
+config BCM2835_MBOX
+	tristate "BCM2835 Mailbox"
+	depends on ARCH_BCM2835
+	help
+	  An implementation of the BCM2385 Mailbox.  It is used to invoke
+	  the services of the Videocore. Say Y here if you want to use the
+	  BCM2835 Mailbox.
+
 endif

drivers/mailbox/Makefile

@@ -11,3 +11,5 @@ obj-$(CONFIG_OMAP2PLUS_MBOX)	+= omap-mailbox.o
 obj-$(CONFIG_PCC)		+= pcc.o
 
 obj-$(CONFIG_ALTERA_MBOX)	+= mailbox-altera.o
+
+obj-$(CONFIG_BCM2835_MBOX)	+= bcm2835-mailbox.o

drivers/mailbox/bcm2835-mailbox.c

@@ -0,0 +1,216 @@
+/*
+ *  Copyright (C) 2010,2015 Broadcom
+ *  Copyright (C) 2013-2014 Lubomir Rintel
+ *  Copyright (C) 2013 Craig McGeachie
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This device provides a mechanism for writing to the mailboxes,
+ * that are shared between the ARM and the VideoCore processor
+ *
+ * Parts of the driver are based on:
+ *  - arch/arm/mach-bcm2708/vcio.c file written by Gray Girling that was
+ *    obtained from branch "rpi-3.6.y" of git://github.com/raspberrypi/
+ *    linux.git
+ *  - drivers/mailbox/bcm2835-ipc.c by Lubomir Rintel at
+ *    https://github.com/hackerspace/rpi-linux/blob/lr-raspberry-pi/drivers/
+ *    mailbox/bcm2835-ipc.c
+ *  - documentation available on the following web site:
+ *    https://github.com/raspberrypi/firmware/wiki/Mailbox-property-interface
+ */
+
+#include <linux/device.h>
+#include <linux/dma-mapping.h>
+#include <linux/err.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/kernel.h>
+#include <linux/mailbox_controller.h>
+#include <linux/module.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+#include <linux/platform_device.h>
+#include <linux/spinlock.h>
+
+/* Mailboxes */
+#define ARM_0_MAIL0	0x00
+#define ARM_0_MAIL1	0x20
+
+/*
+ * Mailbox registers. We basically only support mailbox 0 & 1. We
+ * deliver to the VC in mailbox 1, it delivers to us in mailbox 0. See
+ * BCM2835-ARM-Peripherals.pdf section 1.3 for an explanation about
+ * the placement of memory barriers.
+ */
+#define MAIL0_RD	(ARM_0_MAIL0 + 0x00)
+#define MAIL0_POL	(ARM_0_MAIL0 + 0x10)
+#define MAIL0_STA	(ARM_0_MAIL0 + 0x18)
+#define MAIL0_CNF	(ARM_0_MAIL0 + 0x1C)
+#define MAIL1_WRT	(ARM_0_MAIL1 + 0x00)
+
+/* Status register: FIFO state. */
+#define ARM_MS_FULL		BIT(31)
+#define ARM_MS_EMPTY		BIT(30)
+
+/* Configuration register: Enable interrupts. */
+#define ARM_MC_IHAVEDATAIRQEN	BIT(0)
+
+struct bcm2835_mbox {
+	void __iomem *regs;
+	spinlock_t lock;
+	struct mbox_controller controller;
+};
+
+static struct bcm2835_mbox *bcm2835_link_mbox(struct mbox_chan *link)
+{
+	return container_of(link->mbox, struct bcm2835_mbox, controller);
+}
+
+static irqreturn_t bcm2835_mbox_irq(int irq, void *dev_id)
+{
+	struct bcm2835_mbox *mbox = dev_id;
+	struct device *dev = mbox->controller.dev;
+	struct mbox_chan *link = &mbox->controller.chans[0];
+
+	while (!(readl(mbox->regs + MAIL0_STA) & ARM_MS_EMPTY)) {
+		u32 msg = readl(mbox->regs + MAIL0_RD);
+		dev_dbg(dev, "Reply 0x%08X\n", msg);
+		mbox_chan_received_data(link, &msg);
+	}
+	return IRQ_HANDLED;
+}
+
+static int bcm2835_send_data(struct mbox_chan *link, void *data)
+{
+	struct bcm2835_mbox *mbox = bcm2835_link_mbox(link);
+	u32 msg = *(u32 *)data;
+
+	spin_lock(&mbox->lock);
+	writel(msg, mbox->regs + MAIL1_WRT);
+	dev_dbg(mbox->controller.dev, "Request 0x%08X\n", msg);
+	spin_unlock(&mbox->lock);
+	return 0;
+}
+
+static int bcm2835_startup(struct mbox_chan *link)
+{
+	struct bcm2835_mbox *mbox = bcm2835_link_mbox(link);
+
+	/* Enable the interrupt on data reception */
+	writel(ARM_MC_IHAVEDATAIRQEN, mbox->regs + MAIL0_CNF);
+
+	return 0;
+}
+
+static void bcm2835_shutdown(struct mbox_chan *link)
+{
+	struct bcm2835_mbox *mbox = bcm2835_link_mbox(link);
+
+	writel(0, mbox->regs + MAIL0_CNF);
+}
+
+static bool bcm2835_last_tx_done(struct mbox_chan *link)
+{
+	struct bcm2835_mbox *mbox = bcm2835_link_mbox(link);
+	bool ret;
+
+	spin_lock(&mbox->lock);
+	ret = !(readl(mbox->regs + MAIL0_STA) & ARM_MS_FULL);
+	spin_unlock(&mbox->lock);
+	return ret;
+}
+
+static const struct mbox_chan_ops bcm2835_mbox_chan_ops = {
+	.send_data	= bcm2835_send_data,
+	.startup	= bcm2835_startup,
+	.shutdown	= bcm2835_shutdown,
+	.last_tx_done	= bcm2835_last_tx_done
+};
+
+static struct mbox_chan *bcm2835_mbox_index_xlate(struct mbox_controller *mbox,
+		    const struct of_phandle_args *sp)
+{
+	if (sp->args_count != 0)
+		return NULL;
+
+	return &mbox->chans[0];
+}
+
+static int bcm2835_mbox_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	int ret = 0;
+	struct resource *iomem;
+	struct bcm2835_mbox *mbox;
+
+	mbox = devm_kzalloc(dev, sizeof(*mbox), GFP_KERNEL);
+	if (mbox == NULL)
+		return -ENOMEM;
+	spin_lock_init(&mbox->lock);
+
+	ret = devm_request_irq(dev, irq_of_parse_and_map(dev->of_node, 0),
+			       bcm2835_mbox_irq, 0, dev_name(dev), mbox);
+	if (ret) {
+		dev_err(dev, "Failed to register a mailbox IRQ handler: %d\n",
+			ret);
+		return -ENODEV;
+	}
+
+	iomem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	mbox->regs = devm_ioremap_resource(&pdev->dev, iomem);
+	if (IS_ERR(mbox->regs)) {
+		ret = PTR_ERR(mbox->regs);
+		dev_err(&pdev->dev, "Failed to remap mailbox regs: %d\n", ret);
+		return ret;
+	}
+
+	mbox->controller.txdone_poll = true;
+	mbox->controller.txpoll_period = 5;
+	mbox->controller.ops = &bcm2835_mbox_chan_ops;
+	mbox->controller.of_xlate = &bcm2835_mbox_index_xlate;
+	mbox->controller.dev = dev;
+	mbox->controller.num_chans = 1;
+	mbox->controller.chans = devm_kzalloc(dev,
+		sizeof(*mbox->controller.chans), GFP_KERNEL);
+	if (!mbox->controller.chans)
+		return -ENOMEM;
+
+	ret = mbox_controller_register(&mbox->controller);
+	if (ret)
+		return ret;
+
+	platform_set_drvdata(pdev, mbox);
+	dev_info(dev, "mailbox enabled\n");
+
+	return ret;
+}
+
+static int bcm2835_mbox_remove(struct platform_device *pdev)
+{
+	struct bcm2835_mbox *mbox = platform_get_drvdata(pdev);
+	mbox_controller_unregister(&mbox->controller);
+	return 0;
+}
+
+static const struct of_device_id bcm2835_mbox_of_match[] = {
+	{ .compatible = "brcm,bcm2835-mbox", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, bcm2835_mbox_of_match);
+
+static struct platform_driver bcm2835_mbox_driver = {
+	.driver = {
+		.name = "bcm2835-mbox",
+		.owner = THIS_MODULE,
+		.of_match_table = bcm2835_mbox_of_match,
+	},
+	.probe		= bcm2835_mbox_probe,
+	.remove		= bcm2835_mbox_remove,
+};
+module_platform_driver(bcm2835_mbox_driver);
+
+MODULE_AUTHOR("Lubomir Rintel <lkundrak@v3.sk>");
+MODULE_DESCRIPTION("BCM2835 mailbox IPC driver");
+MODULE_LICENSE("GPL v2");