bcm2835-virtgpio: Virtual GPIO driver

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

gpio: bcm-virt: Fix the get() method

The get() method does not understand the on-the-wire encoding of the
remote GPIO states, thinking they are simple on/off bits when they are
really pairs of 16-bit counts. Rewrite the get() handler to return the
value last written, which will eventually match the actual GPIO state
if there are no other changes.

See: #4638

Signed-off-by: Phil Elwell <phil@raspberrypi.com>

bcm2835-virtgpio: Update for Linux 6.6

The gpio subsystem is happier if the gpiochip is given a parent, and
if it doesn't have a fixed base gpio number. While we're in here,
use the fact that the firmware node is the parent to locate it,
and use the devm_ version of rpi_firmware_get.

Signed-off-by: Phil Elwell <phil@raspberrypi.com>

drivers/gpio/Kconfig

@@ -216,6 +216,12 @@ config GPIO_BCM_XGS_IPROC
 	help
 	  Say yes here to enable GPIO support for Broadcom XGS iProc SoCs.
 
+config GPIO_BCM_VIRT
+	bool "Broadcom Virt GPIO"
+	depends on OF_GPIO && RASPBERRYPI_FIRMWARE && (ARCH_BCM2835 || COMPILE_TEST)
+	help
+	  Turn on virtual GPIO support for Broadcom BCM283X chips.
+
 config GPIO_BRCMSTB
 	tristate "BRCMSTB GPIO support"
 	default y if (ARCH_BRCMSTB || BMIPS_GENERIC)

drivers/gpio/Makefile

@@ -38,6 +38,7 @@ obj-$(CONFIG_GPIO_ASPEED_SGPIO)		+= gpio-aspeed-sgpio.o
 obj-$(CONFIG_GPIO_ATH79)		+= gpio-ath79.o
 obj-$(CONFIG_GPIO_BCM_KONA)		+= gpio-bcm-kona.o
 obj-$(CONFIG_GPIO_BCM_XGS_IPROC)	+= gpio-xgs-iproc.o
+obj-$(CONFIG_GPIO_BCM_VIRT)		+= gpio-bcm-virt.o
 obj-$(CONFIG_GPIO_BD71815)		+= gpio-bd71815.o
 obj-$(CONFIG_GPIO_BD71828)		+= gpio-bd71828.o
 obj-$(CONFIG_GPIO_BD9571MWV)		+= gpio-bd9571mwv.o

drivers/gpio/gpio-bcm-virt.c

@@ -0,0 +1,212 @@
+/*
+ *  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/driver.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/dma-mapping.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];
+	dma_addr_t		bus_addr;
+};
+
+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 (s16)((v >> 16) - v) > 0;
+}
+
+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)
+{
+	int err = 0;
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev_of_node(dev);
+	struct device_node *fw_node;
+	struct rpi_firmware *fw;
+	struct brcmvirt_gpio *ucb;
+	u32 gpiovirtbuf;
+
+	fw_node = of_get_parent(np);
+	if (!fw_node) {
+		dev_err(dev, "Missing firmware node\n");
+		return -ENOENT;
+	}
+
+	fw = devm_rpi_firmware_get(&pdev->dev, fw_node);
+	of_node_put(fw_node);
+	if (!fw)
+		return -EPROBE_DEFER;
+
+	ucb = devm_kzalloc(dev, sizeof *ucb, GFP_KERNEL);
+	if (!ucb) {
+		err = -EINVAL;
+		goto out;
+	}
+
+	ucb->ts_base = dma_alloc_coherent(dev, PAGE_SIZE, &ucb->bus_addr, GFP_KERNEL);
+	if (!ucb->ts_base) {
+		pr_err("[%s]: failed to dma_alloc_coherent(%ld)\n",
+				__func__, PAGE_SIZE);
+		err = -ENOMEM;
+		goto out;
+	}
+
+	gpiovirtbuf = (u32)ucb->bus_addr;
+	err = rpi_firmware_property(fw, RPI_FIRMWARE_FRAMEBUFFER_SET_GPIOVIRTBUF,
+				    &gpiovirtbuf, sizeof(gpiovirtbuf));
+
+	if (err || gpiovirtbuf != 0) {
+		dev_warn(dev, "Failed to set gpiovirtbuf, trying to get err:%x\n", err);
+		dma_free_coherent(dev, PAGE_SIZE, ucb->ts_base, ucb->bus_addr);
+		ucb->ts_base = 0;
+		ucb->bus_addr = 0;
+	}
+
+	if (!ucb->ts_base) {
+		err = rpi_firmware_property(fw, RPI_FIRMWARE_FRAMEBUFFER_GET_GPIOVIRTBUF,
+					    &gpiovirtbuf, sizeof(gpiovirtbuf));
+
+		if (err) {
+			dev_err(dev, "Failed to get gpiovirtbuf\n");
+			goto out;
+		}
+
+		if (!gpiovirtbuf) {
+			dev_err(dev, "No virtgpio buffer\n");
+			err = -ENOENT;
+			goto out;
+		}
+
+		// 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 out;
+		}
+		ucb->bus_addr = 0;
+	}
+	ucb->gc.parent = dev;
+	ucb->gc.label = MODULE_NAME;
+	ucb->gc.owner = THIS_MODULE;
+	ucb->gc.base = -1;
+	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_data(&ucb->gc, NULL);
+	if (err)
+		goto out;
+
+	platform_set_drvdata(pdev, ucb);
+
+	return 0;
+out:
+	if (ucb->bus_addr) {
+		dma_free_coherent(dev, PAGE_SIZE, ucb->ts_base, ucb->bus_addr);
+		ucb->bus_addr = 0;
+		ucb->ts_base = NULL;
+	} else if (ucb->ts_base) {
+		iounmap(ucb->ts_base);
+		ucb->ts_base = NULL;
+	}
+	return err;
+}
+
+static void brcmvirt_gpio_remove(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct brcmvirt_gpio *ucb = platform_get_drvdata(pdev);
+
+	gpiochip_remove(&ucb->gc);
+	if (ucb->bus_addr)
+		dma_free_coherent(dev, PAGE_SIZE, ucb->ts_base, ucb->bus_addr);
+	else if (ucb->ts_base)
+		iounmap(ucb->ts_base);
+}
+
+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");