[PATCH anybus v4 2/7] fieldbus: support the Arcx anybus bridge

[thesven73]

Add a driver for the Arcx anybus bridge.

This chip embeds up to two Anybus-S application connectors
(slots), and connects to the SoC via a parallel memory bus.
There is also a CAN power readout, unrelated to the Anybus,
modelled as a regulator.

Signed-off-by: Sven Van Asbroeck <svendev@xxxxxxxx>
---
 drivers/fieldbus/Kconfig         |  10 +
 drivers/fieldbus/Makefile        |   1 +
 drivers/fieldbus/anybus-bridge.c | 321 +++++++++++++++++++++++++++++++
 3 files changed, 332 insertions(+)
 create mode 100644 drivers/fieldbus/anybus-bridge.c

diff --git a/drivers/fieldbus/Kconfig b/drivers/fieldbus/Kconfig
index 1d1929ba7e27..fc2e20b59b38 100644
--- a/drivers/fieldbus/Kconfig
+++ b/drivers/fieldbus/Kconfig
@@ -16,4 +16,14 @@ menuconfig FIELDBUS_DEV
 
 if FIELDBUS_DEV
 
+config ARCX_ANYBUS_BRIDGE
+	tristate "Arcx Anybus-S Bridge"
+	depends on OF && GPIOLIB
+	help
+	  Select this to get support for the Arcx Anybus bridge.
+	  It connects to the SoC via a parallel memory bus, and
+	  embeds up to two Anybus-S application connectors (slots).
+	  There is also a CAN power readout, unrelated to the Anybus,
+	  modelled as a regulator.
+
 endif
diff --git a/drivers/fieldbus/Makefile b/drivers/fieldbus/Makefile
index 768a116fc9c6..a623722aace6 100644
--- a/drivers/fieldbus/Makefile
+++ b/drivers/fieldbus/Makefile
@@ -7,3 +7,4 @@ obj-$(CONFIG_FIELDBUS_DEV)	+= fieldbus_dev_core.o
 fieldbus_dev_core-y		:= dev_core.o
 
 # Devices
+obj-$(CONFIG_ARCX_ANYBUS_BRIDGE) += anybus-bridge.o
diff --git a/drivers/fieldbus/anybus-bridge.c b/drivers/fieldbus/anybus-bridge.c
new file mode 100644
index 000000000000..9eee39efc3aa
--- /dev/null
+++ b/drivers/fieldbus/anybus-bridge.c
@@ -0,0 +1,321 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Arcx Anybus Bridge driver
+ *
+ * Copyright (C) 2018 Arcx Inc
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/platform_device.h>
+#include <linux/gpio/consumer.h>
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/delay.h>
+#include <linux/idr.h>
+#include <linux/spinlock.h>
+#include <linux/reset-controller.h>
+#include <linux/regulator/driver.h>
+#include <linux/regulator/machine.h>
+
+#define CPLD_STATUS1		0x80
+#define CPLD_CONTROL		0x80
+#define CPLD_CONTROL_CRST	0x40
+#define CPLD_CONTROL_RST1	0x04
+#define CPLD_CONTROL_RST2	0x80
+#define CPLD_STATUS1_AB		0x02
+#define CPLD_STATUS1_CAN_POWER	0x01
+#define CPLD_DESIGN_LO		0x81
+#define CPLD_DESIGN_HI		0x82
+#define CPLD_CAP		0x83
+#define CPLD_CAP_COMPAT		0x01
+#define CPLD_CAP_SEP_RESETS	0x02
+
+struct bridge_priv {
+	struct device *class_dev;
+	struct reset_controller_dev rcdev;
+	bool common_reset;
+	struct gpio_desc *reset_gpiod;
+	void __iomem *cpld_base;
+	spinlock_t regs_lock;
+	u8 control_reg;
+	char version[3];
+	u16 design_no;
+};
+
+static void do_reset(struct bridge_priv *cd, u8 rst_bit, bool reset)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&cd->regs_lock, flags);
+	/*
+	 * CPLD_CONTROL is write-only, so cache its value in
+	 * cd->control_reg
+	 */
+	if (reset)
+		cd->control_reg &= ~rst_bit;
+	else
+		cd->control_reg |= rst_bit;
+	writeb(cd->control_reg, cd->cpld_base + CPLD_CONTROL);
+	/*
+	 * h/w work-around:
+	 * the hardware is 'too fast', so a reset followed by an immediate
+	 * not-reset will _not_ change the anybus reset line in any way,
+	 * losing the reset. to prevent this from happening, introduce
+	 * a minimum reset duration.
+	 * Verified minimum safe duration required using a scope
+	 * on 14-June-2018: 100 us.
+	 */
+	if (reset)
+		udelay(100);
+	spin_unlock_irqrestore(&cd->regs_lock, flags);
+}
+
+static int anybuss_reset(struct bridge_priv *cd,
+			     unsigned long id, bool reset)
+{
+	if (id >= 2)
+		return -EINVAL;
+	if (cd->common_reset)
+		do_reset(cd, CPLD_CONTROL_CRST, reset);
+	else
+		do_reset(cd, id ? CPLD_CONTROL_RST2 : CPLD_CONTROL_RST1, reset);
+	return 0;
+}
+
+static int anybuss_reset_assert(struct reset_controller_dev *rcdev,
+			     unsigned long id)
+{
+	struct bridge_priv *cd = container_of(rcdev, struct bridge_priv, rcdev);
+
+	return anybuss_reset(cd, id, true);
+}
+
+static int anybuss_reset_deassert(struct reset_controller_dev *rcdev,
+			     unsigned long id)
+{
+	struct bridge_priv *cd = container_of(rcdev, struct bridge_priv, rcdev);
+
+	return anybuss_reset(cd, id, false);
+}
+
+static const struct reset_control_ops anybuss_reset_ops = {
+	.assert		= anybuss_reset_assert,
+	.deassert	= anybuss_reset_deassert,
+};
+
+static ssize_t version_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct bridge_priv *cd = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%s\n", cd->version);
+}
+static DEVICE_ATTR_RO(version);
+
+static ssize_t design_number_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct bridge_priv *cd = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%d\n", cd->design_no);
+}
+static DEVICE_ATTR_RO(design_number);
+
+static struct attribute *bridge_attributes[] = {
+	&dev_attr_version.attr,
+	&dev_attr_design_number.attr,
+	NULL,
+};
+
+static struct attribute_group bridge_attribute_group = {
+	.attrs = bridge_attributes,
+};
+
+static const struct attribute_group *bridge_attribute_groups[] = {
+	&bridge_attribute_group,
+	NULL,
+};
+
+static void bridge_device_release(struct device *dev)
+{
+	kfree(dev);
+}
+
+static int can_power_is_enabled(struct regulator_dev *rdev)
+{
+	struct bridge_priv *cd = rdev_get_drvdata(rdev);
+
+	return !(readb(cd->cpld_base + CPLD_STATUS1) & CPLD_STATUS1_CAN_POWER);
+}
+
+static struct regulator_ops can_power_ops = {
+	.is_enabled = can_power_is_enabled,
+};
+
+static const struct regulator_desc can_power_desc = {
+	.name = "regulator-can-power",
+	.id = -1,
+	.type = REGULATOR_VOLTAGE,
+	.owner = THIS_MODULE,
+	.ops = &can_power_ops,
+};
+
+static struct class *bridge_class;
+static DEFINE_IDA(bridge_index_ida);
+
+static int bridge_probe(struct platform_device *pdev)
+{
+	struct bridge_priv *cd;
+	struct device *dev = &pdev->dev;
+	struct regulator_config config = { };
+	struct regulator_dev *regulator;
+	int err, id;
+	struct resource *res;
+	u8 status1, cap;
+
+	cd = devm_kzalloc(dev, sizeof(*cd), GFP_KERNEL);
+	if (!cd)
+		return -ENOMEM;
+	dev_set_drvdata(dev, cd);
+	spin_lock_init(&cd->regs_lock);
+	cd->reset_gpiod = devm_gpiod_get(dev, "reset", GPIOD_OUT_LOW);
+	if (IS_ERR(cd->reset_gpiod))
+		return PTR_ERR(cd->reset_gpiod);
+
+	/* CPLD control memory, sits at index 0 */
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	cd->cpld_base = devm_ioremap_resource(dev, res);
+	if (IS_ERR(cd->cpld_base)) {
+		dev_err(dev,
+			"failed to map cpld base address\n");
+		err = PTR_ERR(cd->cpld_base);
+		goto out_reset;
+	}
+
+	/* identify cpld */
+	status1 = readb(cd->cpld_base + CPLD_STATUS1);
+	cd->design_no = (readb(cd->cpld_base + CPLD_DESIGN_HI) << 8) |
+				readb(cd->cpld_base + CPLD_DESIGN_LO);
+	snprintf(cd->version, sizeof(cd->version), "%c%d",
+			'A' + ((status1>>5) & 0x7),
+			(status1>>2) & 0x7);
+	dev_info(dev, "Bridge is design number %d, revision %s\n",
+		cd->design_no,
+		cd->version);
+	cap = readb(cd->cpld_base + CPLD_CAP);
+	if (!(cap & CPLD_CAP_COMPAT)) {
+		dev_err(dev, "unsupported bridge [cap=0x%02X]", cap);
+		err = -ENODEV;
+		goto out_reset;
+	}
+
+	if (status1 & CPLD_STATUS1_AB) {
+		dev_info(dev, "Bridge has anybus-S slot(s)");
+		cd->common_reset = !(cap & CPLD_CAP_SEP_RESETS);
+		dev_info(dev, "Bridge supports %s", cd->common_reset ?
+			"a common reset" : "separate resets");
+		cd->rcdev.owner	= THIS_MODULE;
+		cd->rcdev.nr_resets = 2;
+		cd->rcdev.ops = &anybuss_reset_ops;
+		cd->rcdev.of_node = dev->of_node;
+		err = devm_reset_controller_register(dev, &cd->rcdev);
+		if (err)
+			goto out_reset;
+	}
+
+	id = ida_simple_get(&bridge_index_ida, 0, 0, GFP_KERNEL);
+	if (id < 0) {
+		err = id;
+		goto out_reset;
+	}
+	/* export can power readout as a regulator */
+	config.dev = dev;
+	config.driver_data = cd;
+	regulator = devm_regulator_register(dev, &can_power_desc, &config);
+	if (IS_ERR(regulator)) {
+		err = PTR_ERR(regulator);
+		goto out_reset;
+	}
+	/* make bridge info visible to userspace */
+	cd->class_dev = kzalloc(sizeof(*cd->class_dev), GFP_KERNEL);
+	if (!cd->class_dev) {
+		err = -ENOMEM;
+		goto out_ida;
+	}
+	cd->class_dev->class = bridge_class;
+	cd->class_dev->groups = bridge_attribute_groups;
+	cd->class_dev->parent = dev;
+	cd->class_dev->id = id;
+	cd->class_dev->release = bridge_device_release;
+	dev_set_name(cd->class_dev, "bridge%d", cd->class_dev->id);
+	dev_set_drvdata(cd->class_dev, cd);
+	err = device_register(cd->class_dev);
+	if (err)
+		goto out_dev;
+	return 0;
+out_dev:
+	put_device(cd->class_dev);
+out_ida:
+	ida_simple_remove(&bridge_index_ida, id);
+out_reset:
+	gpiod_set_value_cansleep(cd->reset_gpiod, 1);
+	return err;
+}
+
+static int bridge_remove(struct platform_device *pdev)
+{
+	struct bridge_priv *cd = platform_get_drvdata(pdev);
+	int id = cd->class_dev->id;
+
+	device_unregister(cd->class_dev);
+	ida_simple_remove(&bridge_index_ida, id);
+	gpiod_set_value_cansleep(cd->reset_gpiod, 1);
+	return 0;
+}
+
+static const struct of_device_id bridge_of_match[] = {
+	{ .compatible = "arcx,anybus-bridge" },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(of, bridge_of_match);
+
+static struct platform_driver bridge_driver = {
+	.probe = bridge_probe,
+	.remove = bridge_remove,
+	.driver		= {
+		.name   = "arcx-anybus-bridge",
+		.owner	= THIS_MODULE,
+		.of_match_table	= of_match_ptr(bridge_of_match),
+	},
+};
+
+static int __init bridge_init(void)
+{
+	int err;
+
+	bridge_class = class_create(THIS_MODULE, "arcx_anybus_bridge");
+	if (!IS_ERR(bridge_class)) {
+		err = platform_driver_register(&bridge_driver);
+		if (err)
+			class_destroy(bridge_class);
+	} else
+		err = PTR_ERR(bridge_class);
+	return err;
+}
+
+static void __exit bridge_exit(void)
+{
+	platform_driver_unregister(&bridge_driver);
+	class_destroy(bridge_class);
+}
+
+module_init(bridge_init);
+module_exit(bridge_exit);
+
+MODULE_DESCRIPTION("Arcx Anybus Bridge driver");
+MODULE_AUTHOR("Sven Van Asbroeck <svendev@xxxxxxxx>");
+MODULE_LICENSE("GPL v2");
-- 
2.17.1