bcm2835-virtgpio: Virtual GPIO driver

Add a virtual GPIO driver that uses the firmware mailbox interface to
request that the VPU toggles LEDs.

arch/arm/configs/bcm2709_defconfig

@@ -607,6 +607,7 @@ CONFIG_PPS=m
 CONFIG_PPS_CLIENT_LDISC=m
 CONFIG_PPS_CLIENT_GPIO=m
 CONFIG_GPIO_SYSFS=y
+CONFIG_GPIO_BCM_VIRT=y
 CONFIG_GPIO_ARIZONA=m
 CONFIG_GPIO_STMPE=y
 CONFIG_W1=m

drivers/gpio/Kconfig

@@ -132,6 +132,12 @@ config GPIO_BCM_KONA
 	help
 	  Turn on GPIO support for Broadcom "Kona" chips.
 
+config GPIO_BCM_VIRT
+	bool "Broadcom Virt GPIO"
+	depends on OF_GPIO && RASPBERRYPI_FIRMWARE && (ARCH_BCM2835 || ARCH_BCM2708 || ARCH_BCM2709 || COMPILE_TEST)
+	help
+	  Turn on virtual GPIO support for Broadcom BCM283X chips.
+
 config GPIO_BRCMSTB
 	tristate "BRCMSTB GPIO support"
 	default y if ARCH_BRCMSTB

drivers/gpio/Makefile

@@ -24,6 +24,7 @@ obj-$(CONFIG_GPIO_AMDPT)	+= gpio-amdpt.o
 obj-$(CONFIG_GPIO_ARIZONA)	+= gpio-arizona.o
 obj-$(CONFIG_ATH79)		+= gpio-ath79.o
 obj-$(CONFIG_GPIO_BCM_KONA)	+= gpio-bcm-kona.o
+obj-$(CONFIG_GPIO_BCM_VIRT)	+= gpio-bcm-virt.o
 obj-$(CONFIG_GPIO_BRCMSTB)	+= gpio-brcmstb.o
 obj-$(CONFIG_GPIO_BT8XX)	+= gpio-bt8xx.o
 obj-$(CONFIG_GPIO_CLPS711X)	+= gpio-clps711x.o

drivers/gpio/gpio-bcm-virt.c

@@ -0,0 +1,180 @@
+/*
+ *  brcmvirt GPIO driver
+ *
+ *  Copyright (C) 2012,2013 Dom Cobley <popcornmix@gmail.com>
+ *  Based on gpio-clps711x.c by Alexander Shiyan <shc_work@mail.ru>
+ *
+ * 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/err.h>
+#include <linux/gpio.h>
+#include <linux/module.h>
+#include <linux/basic_mmio_gpio.h>
+#include <linux/platform_device.h>
+#include <soc/bcm2835/raspberrypi-firmware.h>
+
+#define MODULE_NAME "brcmvirt-gpio"
+#define NUM_GPIO 2
+
+struct brcmvirt_gpio {
+	struct gpio_chip	gc;
+	u32 __iomem		*ts_base;
+	/* two packed 16-bit counts of enabled and disables
+           Allows host to detect a brief enable that was missed */
+	u32			enables_disables[NUM_GPIO];
+};
+
+static int brcmvirt_gpio_dir_in(struct gpio_chip *gc, unsigned off)
+{
+	struct brcmvirt_gpio *gpio;
+	gpio = container_of(gc, struct brcmvirt_gpio, gc);
+	return -EINVAL;
+}
+
+static int brcmvirt_gpio_dir_out(struct gpio_chip *gc, unsigned off, int val)
+{
+	struct brcmvirt_gpio *gpio;
+	gpio = container_of(gc, struct brcmvirt_gpio, gc);
+	return 0;
+}
+
+static int brcmvirt_gpio_get(struct gpio_chip *gc, unsigned off)
+{
+	struct brcmvirt_gpio *gpio;
+	unsigned v;
+	gpio = container_of(gc, struct brcmvirt_gpio, gc);
+	v = readl(gpio->ts_base + off);
+	return (v >> off) & 1;
+}
+
+static void brcmvirt_gpio_set(struct gpio_chip *gc, unsigned off, int val)
+{
+	struct brcmvirt_gpio *gpio;
+	u16 enables, disables;
+	s16 diff;
+	bool lit;
+	gpio = container_of(gc, struct brcmvirt_gpio, gc);
+	enables  = gpio->enables_disables[off] >> 16;
+	disables = gpio->enables_disables[off] >>  0;
+	diff = (s16)(enables - disables);
+	lit = diff > 0;
+	if ((val && lit) || (!val && !lit))
+		return;
+	if (val)
+		enables++;
+	else
+		disables++;
+	diff = (s16)(enables - disables);
+	BUG_ON(diff != 0 && diff != 1);
+	gpio->enables_disables[off] = (enables << 16) | (disables << 0);
+	writel(gpio->enables_disables[off], gpio->ts_base + off);
+}
+
+static int brcmvirt_gpio_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node;
+	struct device_node *fw_node;
+	struct rpi_firmware *fw;
+	struct brcmvirt_gpio *ucb;
+	u32 gpiovirtbuf;
+	int err = 0;
+
+	fw_node = of_parse_phandle(np, "firmware", 0);
+	if (!fw_node) {
+		dev_err(dev, "Missing firmware node\n");
+		return -ENOENT;
+	}
+
+	fw = rpi_firmware_get(fw_node);
+	if (!fw)
+		return -EPROBE_DEFER;
+
+	err = rpi_firmware_property(fw, RPI_FIRMWARE_FRAMEBUFFER_GET_GPIOVIRTBUF,
+				    &gpiovirtbuf, sizeof(gpiovirtbuf));
+
+	if (err) {
+		dev_err(dev, "Failed to get gpiovirtbuf\n");
+		goto err;
+	}
+
+	if (!gpiovirtbuf) {
+		dev_err(dev, "No virtgpio buffer\n");
+		err = -ENOENT;
+		goto err;
+	}
+
+	ucb = devm_kzalloc(dev, sizeof *ucb, GFP_KERNEL);
+	if (!ucb) {
+		err = -EINVAL;
+		goto err;
+	}
+
+	// mmap the physical memory
+	gpiovirtbuf &= ~0xc0000000;
+	ucb->ts_base = ioremap(gpiovirtbuf, 4096);
+	if (ucb->ts_base == NULL) {
+		dev_err(dev, "Failed to map physical address\n");
+		err = -ENOENT;
+		goto err;
+	}
+
+	ucb->gc.label = MODULE_NAME;
+	ucb->gc.owner = THIS_MODULE;
+	ucb->gc.dev = dev;
+	ucb->gc.of_node = np;
+	ucb->gc.base = 100;
+	ucb->gc.ngpio = NUM_GPIO;
+
+	ucb->gc.direction_input = brcmvirt_gpio_dir_in;
+	ucb->gc.direction_output = brcmvirt_gpio_dir_out;
+	ucb->gc.get = brcmvirt_gpio_get;
+	ucb->gc.set = brcmvirt_gpio_set;
+	ucb->gc.can_sleep = true;
+
+	err = gpiochip_add(&ucb->gc);
+	if (err)
+		goto err;
+
+	platform_set_drvdata(pdev, ucb);
+
+err:
+	return err;
+
+}
+
+static int brcmvirt_gpio_remove(struct platform_device *pdev)
+{
+	int err = 0;
+	struct brcmvirt_gpio *ucb = platform_get_drvdata(pdev);
+
+	gpiochip_remove(&ucb->gc);
+	iounmap(ucb->ts_base);
+	return err;
+}
+
+static const struct of_device_id __maybe_unused brcmvirt_gpio_ids[] = {
+	{ .compatible = "brcm,bcm2835-virtgpio" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, brcmvirt_gpio_ids);
+
+static struct platform_driver brcmvirt_gpio_driver = {
+	.driver	= {
+		.name		= MODULE_NAME,
+		.owner		= THIS_MODULE,
+		.of_match_table	= of_match_ptr(brcmvirt_gpio_ids),
+	},
+	.probe	= brcmvirt_gpio_probe,
+	.remove	= brcmvirt_gpio_remove,
+};
+module_platform_driver(brcmvirt_gpio_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Dom Cobley <popcornmix@gmail.com>");
+MODULE_DESCRIPTION("brcmvirt GPIO driver");
+MODULE_ALIAS("platform:brcmvirt-gpio");

include/soc/bcm2835/raspberrypi-firmware.h

@@ -93,6 +93,7 @@ enum rpi_firmware_property_tag {
 	RPI_FIRMWARE_FRAMEBUFFER_GET_OVERSCAN =               0x0004000a,
 	RPI_FIRMWARE_FRAMEBUFFER_GET_PALETTE =                0x0004000b,
 	RPI_FIRMWARE_FRAMEBUFFER_GET_TOUCHBUF =               0x0004000f,
+	RPI_FIRMWARE_FRAMEBUFFER_GET_GPIOVIRTBUF =            0x00040010,
 	RPI_FIRMWARE_FRAMEBUFFER_RELEASE =                    0x00048001,
 	RPI_FIRMWARE_FRAMEBUFFER_TEST_PHYSICAL_WIDTH_HEIGHT = 0x00044003,
 	RPI_FIRMWARE_FRAMEBUFFER_TEST_VIRTUAL_WIDTH_HEIGHT =  0x00044004,