[RFC] mailbox: Add Broadcom BCM2835 mailbox driver
Lubomir Rintel
lkundrak at v3.sk
Wed Apr 17 08:56:32 EDT 2013
Hello!
This adds a driver for mailbox IPC mechanism present on Broadcom
BCM2835 SoC, used in Raspberry Pi and Roku 2 devices.
Some work-in-progress drivers (as well as device tree bindings, etc.) that
utilize this are here:
https://github.com/hackerspace/rpi-linux/tree/lr-raspberry-pi
https://github.com/hackerspace/rpi-linux/tree/lr-vchiq
I intend to post them for review/inclusion once this driver is in good shape.
I'm really not sure about some decisions made implementing this and am wondering
if you could take a look at this:
1.) How to ensure this driver is loaded before the devices that need it? Is
arch_initcall() appropriate? Shouldn't devices that communicate via mailbox
(thermal, cpufreq, vchiq, framebuffer...) be present underneath the mbox in the
device hierarchy so that we could register them in our probe() only once we've
set up the mailbox?
2.) Is the global struct device for mbox appropriate or should we extend the
exported functions with dev argument and let our users discover the mbox device
via device tree?
.../bindings/mailbox/brcm,bcm2835-mbox.txt | 15 +
drivers/mailbox/Kconfig | 9 +
drivers/mailbox/Makefile | 1 +
drivers/mailbox/bcm2835-ipc.c | 268 ++++++++++++++++++++
include/linux/mailbox.h | 3 +
5 files changed, 296 insertions(+), 0 deletions(-)
create mode 100644 Documentation/devicetree/bindings/mailbox/brcm,bcm2835-mbox.txt
create mode 100644 drivers/mailbox/bcm2835-ipc.c
diff --git a/Documentation/devicetree/bindings/mailbox/brcm,bcm2835-mbox.txt b/Documentation/devicetree/bindings/mailbox/brcm,bcm2835-mbox.txt
new file mode 100644
index 0000000..75dbb89
--- /dev/null
+++ b/Documentation/devicetree/bindings/mailbox/brcm,bcm2835-mbox.txt
@@ -0,0 +1,15 @@
+Broadcom BCM2835 VideoCore mailbox IPC
+
+Required properties:
+
+- compatible : should be "brcm,bcm2835-mbox"
+- reg : Specifies base physical address and size of the registers.
+- interrupts : the interrupt number
+
+Example:
+
+mailbox {
+ compatible = "brcm,bcm2835-mbox";
+ reg = <0x7e00b800 0x400>;
+ interrupts = <0 1>;
+};
diff --git a/drivers/mailbox/Kconfig b/drivers/mailbox/Kconfig
index 9545c9f..052260b 100644
--- a/drivers/mailbox/Kconfig
+++ b/drivers/mailbox/Kconfig
@@ -16,4 +16,13 @@ config PL320_MBOX
Management Engine, primarily for cpufreq. Say Y here if you want
to use the PL320 IPCM support.
+config BCM2835_MBOX
+ bool "BCM2835 VideoCore mailbox"
+ depends on ARCH_BCM2835
+ help
+ This driver provides support for interprocessor communication
+ mechanisms between ARM core and Broadcom BCM2835 VideoCore processor.
+ This processor is used on Raspberry Pi single board computer.
+ Say Y if your device uses such processor.
+
endif
diff --git a/drivers/mailbox/Makefile b/drivers/mailbox/Makefile
index 543ad6a..1de595d 100644
--- a/drivers/mailbox/Makefile
+++ b/drivers/mailbox/Makefile
@@ -1 +1,2 @@
obj-$(CONFIG_PL320_MBOX) += pl320-ipc.o
+obj-$(CONFIG_BCM2835_MBOX) += bcm2835-ipc.o
diff --git a/drivers/mailbox/bcm2835-ipc.c b/drivers/mailbox/bcm2835-ipc.c
new file mode 100644
index 0000000..c61ff3f
--- /dev/null
+++ b/drivers/mailbox/bcm2835-ipc.c
@@ -0,0 +1,268 @@
+/*
+ * Copyright (C) 2010 Broadcom
+ * Copyright (C) 2013 Lubomir Rintel
+ *
+ * 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 as well as documentation
+ * available on the following web site:
+ * https://github.com/raspberrypi/firmware/wiki/Mailbox-property-interface
+ */
+
+#include <linux/module.h>
+#include <linux/completion.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/device.h>
+#include <linux/dma-mapping.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+
+#define BCM2835_MBOX_TIMEOUT HZ
+
+/* Mailboxes */
+#define ARM_0_MAIL0 0x00
+#define ARM_0_MAIL1 0x20
+
+/* Mailbox registers. We basically only support mailbox 0. */
+#define MAIL0_RD (ARM_0_MAIL0 + 0x00)
+#define MAIL0_WRT (ARM_0_MAIL1 + 0x00)
+#define MAIL0_STA (ARM_0_MAIL0 + 0x18)
+#define MAIL0_CNF (ARM_0_MAIL0 + 0x1C)
+
+/* Read/write Channels. Currently we just need the property one. */
+#define MBOX_CHAN_PROPERTY 8
+#define MBOX_CHAN_COUNT 9
+
+/* Status register: FIFO state. */
+#define ARM_MS_FULL 0x80000000
+#define ARM_MS_EMPTY 0x40000000
+
+/* Configuration register: Enable interrupts. */
+#define ARM_MC_IHAVEDATAIRQEN 0x00000001
+
+#define MBOX_MSG(chan, data28) (((data28) & ~0xf) | ((chan) & 0xf))
+#define MBOX_CHAN(msg) ((msg) & 0xf)
+#define MBOX_DATA28(msg) ((msg) & ~0xf)
+
+static struct device *bcm2835_mbox_dev; /* we assume there's only one! */
+
+struct bcm2835_mbox {
+ struct device *dev;
+ void __iomem *regs;
+ struct {
+ u32 msg;
+ struct completion comp;
+ struct mutex lock;
+ } chan[MBOX_CHAN_COUNT];
+};
+
+static irqreturn_t bcm2835_mbox_irq(int irq, void *dev_id)
+{
+ struct bcm2835_mbox *mbox = (struct bcm2835_mbox *)dev_id;
+ struct device *dev = mbox->dev;
+ int ret = IRQ_NONE;
+
+ /* wait for the mailbox FIFO to have some data in it */
+ while (!(readl(mbox->regs + MAIL0_STA) & ARM_MS_EMPTY)) {
+ u32 msg = readl(mbox->regs + MAIL0_RD);
+ unsigned int chan = MBOX_CHAN(msg);
+
+ if (chan > MBOX_CHAN_COUNT) {
+ dev_err(dev, "invalid channel (%d)\n", chan);
+ continue;
+ }
+
+ if (mbox->chan[chan].msg) {
+ dev_err(dev, "overflow on channel (%d)\n", chan);
+ continue;
+ }
+
+ mbox->chan[chan].msg = msg;
+ complete(&mbox->chan[chan].comp);
+
+ ret = IRQ_HANDLED;
+ }
+
+ return ret;
+}
+
+/**
+ * bcm2835_mbox_io() - send a message to BCM2835 mailbox and read a reply
+ * @chan: Channel number
+ * @in28: Message to send
+ * @out28: Where to put the response
+ *
+ * Sends a message to the BCM2835 mailbox.
+ *
+ * If the last argument is non-NULL, a response from VideoCore is awaited
+ * for and written to memory pointed to by it.
+ *
+ * The I/O to property mailbox is more conveniently dealt with by using
+ * bcm2835_mbox_property() function.
+ *
+ * Return: 0 in case of success, otherwise an error code
+ */
+
+int bcm2835_mbox_io(unsigned chan, u32 in28, u32 *out28)
+{
+ struct bcm2835_mbox *mbox;
+ int timeout;
+ int ret = 0;
+
+ if (!bcm2835_mbox_dev)
+ return -ENODEV;
+
+ mbox = dev_get_drvdata(bcm2835_mbox_dev);
+
+ device_lock(bcm2835_mbox_dev);
+ /* wait for the mailbox FIFO to have some space in it */
+ while (readl(mbox->regs + MAIL0_STA) & ARM_MS_FULL)
+ cpu_relax();
+
+ mutex_lock(&mbox->chan[chan].lock);
+ writel(MBOX_MSG(chan, in28), mbox->regs + MAIL0_WRT);
+ device_unlock(bcm2835_mbox_dev);
+
+ /* Don't wait for a response. */
+ if (out28 == NULL)
+ goto out;
+
+ timeout = wait_for_completion_timeout(&mbox->chan[chan].comp,
+ BCM2835_MBOX_TIMEOUT);
+ if (timeout == 0) {
+ dev_warn(bcm2835_mbox_dev, "Channel %d timeout\n", chan);
+ ret = -ETIMEDOUT;
+ goto out;
+ }
+ *out28 = MBOX_DATA28(mbox->chan[chan].msg);
+
+out:
+ mbox->chan[chan].msg = 0;
+ mutex_unlock(&mbox->chan[chan].lock);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(bcm2835_mbox_io);
+
+/**
+ * bcm2835_mbox_property() - Call a BCM2835 Property mailbox service
+ * @mem_bus: DMA address of message
+ *
+ * Sends a message to the BCM2835 property mailbox and wait for VideoCore to
+ * respond. The message memory should be obtained with dma_alloc_coherent()
+ * and be filled with a properly formatted mailbox message.
+ *
+ * Return: 0 in case of success, otherwise an error code
+ */
+
+int bcm2835_mbox_property(dma_addr_t mem_bus)
+{
+ int ret;
+ int val;
+
+ wmb();
+ ret = bcm2835_mbox_io(MBOX_CHAN_PROPERTY, (u32)mem_bus, (u32 *)&val);
+ rmb();
+ if (mem_bus != val) {
+ dev_warn(bcm2835_mbox_dev, "Bad response from property mailbox\n");
+ return -EIO;
+ }
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(bcm2835_mbox_property);
+
+static int bcm2835_mbox_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct device_node *np = dev->of_node;
+ struct bcm2835_mbox *mbox;
+ int irq;
+ int ret;
+ int i;
+
+ mbox = devm_kzalloc(dev, sizeof(*mbox), GFP_KERNEL);
+ if (mbox == NULL) {
+ dev_err(dev, "Failed to allocate mailbox memory\n");
+ return -ENOMEM;
+ }
+
+ /* Initialize the channels */
+ for (i = 0; i < MBOX_CHAN_COUNT; i++) {
+ mbox->chan[i].msg = 0;
+ init_completion(&mbox->chan[i].comp);
+ mutex_init(&mbox->chan[i].lock);
+ }
+
+ platform_set_drvdata(pdev, mbox);
+ mbox->dev = dev;
+
+ irq = irq_of_parse_and_map(np, 0);
+ if (irq <= 0) {
+ dev_err(dev, "Can't get IRQ number for mailbox\n");
+ return -ENODEV;
+ }
+ ret = devm_request_irq(dev, irq, bcm2835_mbox_irq, IRQF_SHARED,
+ dev_name(dev), mbox);
+ if (ret) {
+ dev_err(dev, "Failed to register a mailbox IRQ handler\n");
+ return -ENODEV;
+ }
+
+ mbox->regs = of_iomap(np, 0);
+ if (!mbox->regs) {
+ dev_err(dev, "Failed to remap mailbox regs\n");
+ return -ENODEV;
+ }
+
+ /* Enable the interrupt on data reception */
+ writel(ARM_MC_IHAVEDATAIRQEN, mbox->regs + MAIL0_CNF);
+
+ dev_info(dev, "Broadcom BCM2835 mailbox IPC");
+ bcm2835_mbox_dev = dev;
+
+ return 0;
+}
+
+static int bcm2835_mbox_remove(struct platform_device *pdev)
+{
+ bcm2835_mbox_dev = NULL;
+ 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);
+
+static int __init bcm2835_mbox_init(void)
+{
+ return platform_driver_register(&bcm2835_mbox_driver);
+}
+arch_initcall(bcm2835_mbox_init);
+
+MODULE_AUTHOR("Lubomir Rintel");
+MODULE_DESCRIPTION("BCM2835 mailbox IPC driver");
+MODULE_LICENSE("GPLv2");
diff --git a/include/linux/mailbox.h b/include/linux/mailbox.h
index 5161f63..a9bfded 100644
--- a/include/linux/mailbox.h
+++ b/include/linux/mailbox.h
@@ -15,3 +15,6 @@
int pl320_ipc_transmit(u32 *data);
int pl320_ipc_register_notifier(struct notifier_block *nb);
int pl320_ipc_unregister_notifier(struct notifier_block *nb);
+
+int __must_check bcm2835_mbox_io(unsigned chan, u32 in28, u32 *out28);
+int __must_check bcm2835_mbox_property(dma_addr_t mem_bus);
--
1.7.1
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