i2c-gpio driver fix

i2c-gpio/Makefile

+obj-m = i2c-gpio.o
+KVERSION = $(shell uname -r)
+all:
+	make -C /lib/modules/$(KVERSION)/build M=$(PWD) modules
+clean:
+	make -C /lib/modules/$(KVERSION)/build M=$(PWD) clean

i2c-gpio/i2c-gpio.c

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Bitbanging I2C bus driver using the GPIO API
+ *
+ * Copyright (C) 2007 Atmel Corporation
+ */
+#include <linux/completion.h>
+#include <linux/debugfs.h>
+#include <linux/delay.h>
+#include <linux/gpio/consumer.h>
+#include <linux/i2c-algo-bit.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_data/i2c-gpio.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+struct i2c_gpio_private_data {
+	struct gpio_desc *sda;
+	struct gpio_desc *scl;
+	struct i2c_adapter adap;
+	struct i2c_algo_bit_data bit_data;
+	struct i2c_gpio_platform_data pdata;
+#ifdef CONFIG_I2C_GPIO_FAULT_INJECTOR
+	struct dentry *debug_dir;
+	/* these must be protected by bus lock */
+	struct completion scl_irq_completion;
+	u64 scl_irq_data;
+#endif
+};
+
+/*
+ * Toggle SDA by changing the output value of the pin. This is only
+ * valid for pins configured as open drain (i.e. setting the value
+ * high effectively turns off the output driver.)
+ */
+static void i2c_gpio_setsda_val(void *data, int state)
+{
+	struct i2c_gpio_private_data *priv = data;
+
+	gpiod_set_value_cansleep(priv->sda, state);
+	gpiod_get_value(priv->sda);
+}
+
+/*
+ * Toggle SCL by changing the output value of the pin. This is used
+ * for pins that are configured as open drain and for output-only
+ * pins. The latter case will break the i2c protocol, but it will
+ * often work in practice.
+ */
+static void i2c_gpio_setscl_val(void *data, int state)
+{
+	struct i2c_gpio_private_data *priv = data;
+
+	gpiod_set_value_cansleep(priv->scl, state);
+	gpiod_get_value(priv->scl);
+}
+
+static int i2c_gpio_getsda(void *data)
+{
+	struct i2c_gpio_private_data *priv = data;
+
+	return gpiod_get_value_cansleep(priv->sda);
+}
+
+static int i2c_gpio_getscl(void *data)
+{
+	struct i2c_gpio_private_data *priv = data;
+
+	return gpiod_get_value_cansleep(priv->scl);
+}
+
+#ifdef CONFIG_I2C_GPIO_FAULT_INJECTOR
+static struct dentry *i2c_gpio_debug_dir;
+
+#define setsda(bd, val)	((bd)->setsda((bd)->data, val))
+#define setscl(bd, val)	((bd)->setscl((bd)->data, val))
+#define getsda(bd)	((bd)->getsda((bd)->data))
+#define getscl(bd)	((bd)->getscl((bd)->data))
+
+#define WIRE_ATTRIBUTE(wire) \
+static int fops_##wire##_get(void *data, u64 *val)		\
+{								\
+	struct i2c_gpio_private_data *priv = data;		\
+								\
+	i2c_lock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER);	\
+	*val = get##wire(&priv->bit_data);			\
+	i2c_unlock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER);	\
+	return 0;						\
+}								\
+static int fops_##wire##_set(void *data, u64 val)		\
+{								\
+	struct i2c_gpio_private_data *priv = data;		\
+								\
+	i2c_lock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER);	\
+	set##wire(&priv->bit_data, val);			\
+	i2c_unlock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER);	\
+	return 0;						\
+}								\
+DEFINE_DEBUGFS_ATTRIBUTE(fops_##wire, fops_##wire##_get, fops_##wire##_set, "%llu\n")
+
+WIRE_ATTRIBUTE(scl);
+WIRE_ATTRIBUTE(sda);
+
+static void i2c_gpio_incomplete_transfer(struct i2c_gpio_private_data *priv,
+					u32 pattern, u8 pattern_size)
+{
+	struct i2c_algo_bit_data *bit_data = &priv->bit_data;
+	int i;
+
+	i2c_lock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER);
+
+	/* START condition */
+	setsda(bit_data, 0);
+	udelay(bit_data->udelay);
+
+	/* Send pattern, request ACK, don't send STOP */
+	for (i = pattern_size - 1; i >= 0; i--) {
+		setscl(bit_data, 0);
+		udelay(bit_data->udelay / 2);
+		setsda(bit_data, (pattern >> i) & 1);
+		udelay((bit_data->udelay + 1) / 2);
+		setscl(bit_data, 1);
+		udelay(bit_data->udelay);
+	}
+
+	i2c_unlock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER);
+}
+
+static int fops_incomplete_addr_phase_set(void *data, u64 addr)
+{
+	struct i2c_gpio_private_data *priv = data;
+	u32 pattern;
+
+	if (addr > 0x7f)
+		return -EINVAL;
+
+	/* ADDR (7 bit) + RD (1 bit) + Client ACK, keep SDA hi (1 bit) */
+	pattern = (addr << 2) | 3;
+
+	i2c_gpio_incomplete_transfer(priv, pattern, 9);
+
+	return 0;
+}
+DEFINE_DEBUGFS_ATTRIBUTE(fops_incomplete_addr_phase, NULL, fops_incomplete_addr_phase_set, "%llu\n");
+
+static int fops_incomplete_write_byte_set(void *data, u64 addr)
+{
+	struct i2c_gpio_private_data *priv = data;
+	u32 pattern;
+
+	if (addr > 0x7f)
+		return -EINVAL;
+
+	/* ADDR (7 bit) + WR (1 bit) + Client ACK (1 bit) */
+	pattern = (addr << 2) | 1;
+	/* 0x00 (8 bit) + Client ACK, keep SDA hi (1 bit) */
+	pattern = (pattern << 9) | 1;
+
+	i2c_gpio_incomplete_transfer(priv, pattern, 18);
+
+	return 0;
+}
+DEFINE_DEBUGFS_ATTRIBUTE(fops_incomplete_write_byte, NULL, fops_incomplete_write_byte_set, "%llu\n");
+
+static int i2c_gpio_fi_act_on_scl_irq(struct i2c_gpio_private_data *priv,
+				       irqreturn_t handler(int, void*))
+{
+	int ret, irq = gpiod_to_irq(priv->scl);
+
+	if (irq < 0)
+		return irq;
+
+	i2c_lock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER);
+
+	ret = gpiod_direction_input(priv->scl);
+	if (ret)
+		goto unlock;
+
+	reinit_completion(&priv->scl_irq_completion);
+
+	ret = request_irq(irq, handler, IRQF_TRIGGER_FALLING,
+			  "i2c_gpio_fault_injector_scl_irq", priv);
+	if (ret)
+		goto output;
+
+	wait_for_completion_interruptible(&priv->scl_irq_completion);
+
+	free_irq(irq, priv);
+ output:
+	ret = gpiod_direction_output(priv->scl, 1) ?: ret;
+ unlock:
+	i2c_unlock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER);
+
+	return ret;
+}
+
+static irqreturn_t lose_arbitration_irq(int irq, void *dev_id)
+{
+	struct i2c_gpio_private_data *priv = dev_id;
+
+	setsda(&priv->bit_data, 0);
+	udelay(priv->scl_irq_data);
+	setsda(&priv->bit_data, 1);
+
+	complete(&priv->scl_irq_completion);
+
+	return IRQ_HANDLED;
+}
+
+static int fops_lose_arbitration_set(void *data, u64 duration)
+{
+	struct i2c_gpio_private_data *priv = data;
+
+	if (duration > 100 * 1000)
+		return -EINVAL;
+
+	priv->scl_irq_data = duration;
+	/*
+	 * Interrupt on falling SCL. This ensures that the master under test has
+	 * really started the transfer. Interrupt on falling SDA did only
+	 * exercise 'bus busy' detection on some HW but not 'arbitration lost'.
+	 * Note that the interrupt latency may cause the first bits to be
+	 * transmitted correctly.
+	 */
+	return i2c_gpio_fi_act_on_scl_irq(priv, lose_arbitration_irq);
+}
+DEFINE_DEBUGFS_ATTRIBUTE(fops_lose_arbitration, NULL, fops_lose_arbitration_set, "%llu\n");
+
+static irqreturn_t inject_panic_irq(int irq, void *dev_id)
+{
+	struct i2c_gpio_private_data *priv = dev_id;
+
+	udelay(priv->scl_irq_data);
+	panic("I2C fault injector induced panic");
+
+	return IRQ_HANDLED;
+}
+
+static int fops_inject_panic_set(void *data, u64 duration)
+{
+	struct i2c_gpio_private_data *priv = data;
+
+	if (duration > 100 * 1000)
+		return -EINVAL;
+
+	priv->scl_irq_data = duration;
+	/*
+	 * Interrupt on falling SCL. This ensures that the master under test has
+	 * really started the transfer.
+	 */
+	return i2c_gpio_fi_act_on_scl_irq(priv, inject_panic_irq);
+}
+DEFINE_DEBUGFS_ATTRIBUTE(fops_inject_panic, NULL, fops_inject_panic_set, "%llu\n");
+
+static void i2c_gpio_fault_injector_init(struct platform_device *pdev)
+{
+	struct i2c_gpio_private_data *priv = platform_get_drvdata(pdev);
+
+	/*
+	 * If there will be a debugfs-dir per i2c adapter somewhen, put the
+	 * 'fault-injector' dir there. Until then, we have a global dir with
+	 * all adapters as subdirs.
+	 */
+	if (!i2c_gpio_debug_dir) {
+		i2c_gpio_debug_dir = debugfs_create_dir("i2c-fault-injector", NULL);
+		if (!i2c_gpio_debug_dir)
+			return;
+	}
+
+	priv->debug_dir = debugfs_create_dir(pdev->name, i2c_gpio_debug_dir);
+	if (!priv->debug_dir)
+		return;
+
+	init_completion(&priv->scl_irq_completion);
+
+	debugfs_create_file_unsafe("incomplete_address_phase", 0200, priv->debug_dir,
+				   priv, &fops_incomplete_addr_phase);
+	debugfs_create_file_unsafe("incomplete_write_byte", 0200, priv->debug_dir,
+				   priv, &fops_incomplete_write_byte);
+	if (priv->bit_data.getscl) {
+		debugfs_create_file_unsafe("inject_panic", 0200, priv->debug_dir,
+					   priv, &fops_inject_panic);
+		debugfs_create_file_unsafe("lose_arbitration", 0200, priv->debug_dir,
+					   priv, &fops_lose_arbitration);
+	}
+	debugfs_create_file_unsafe("scl", 0600, priv->debug_dir, priv, &fops_scl);
+	debugfs_create_file_unsafe("sda", 0600, priv->debug_dir, priv, &fops_sda);
+}
+
+static void i2c_gpio_fault_injector_exit(struct platform_device *pdev)
+{
+	struct i2c_gpio_private_data *priv = platform_get_drvdata(pdev);
+
+	debugfs_remove_recursive(priv->debug_dir);
+}
+#else
+static inline void i2c_gpio_fault_injector_init(struct platform_device *pdev) {}
+static inline void i2c_gpio_fault_injector_exit(struct platform_device *pdev) {}
+#endif /* CONFIG_I2C_GPIO_FAULT_INJECTOR*/
+
+static void of_i2c_gpio_get_props(struct device_node *np,
+				  struct i2c_gpio_platform_data *pdata)
+{
+	u32 reg;
+
+	of_property_read_u32(np, "i2c-gpio,delay-us", &pdata->udelay);
+
+	if (!of_property_read_u32(np, "i2c-gpio,timeout-ms", &reg))
+		pdata->timeout = msecs_to_jiffies(reg);
+
+	pdata->sda_is_open_drain =
+		of_property_read_bool(np, "i2c-gpio,sda-open-drain");
+	pdata->scl_is_open_drain =
+		of_property_read_bool(np, "i2c-gpio,scl-open-drain");
+	pdata->scl_is_output_only =
+		of_property_read_bool(np, "i2c-gpio,scl-output-only");
+}
+
+static struct gpio_desc *i2c_gpio_get_desc(struct device *dev,
+					   const char *con_id,
+					   unsigned int index,
+					   enum gpiod_flags gflags)
+{
+	struct gpio_desc *retdesc;
+	int ret;
+
+	retdesc = devm_gpiod_get(dev, con_id, gflags);
+	if (!IS_ERR(retdesc)) {
+		dev_dbg(dev, "got GPIO from name %s\n", con_id);
+		return retdesc;
+	}
+
+	retdesc = devm_gpiod_get_index(dev, NULL, index, gflags);
+	if (!IS_ERR(retdesc)) {
+		dev_dbg(dev, "got GPIO from index %u\n", index);
+		return retdesc;
+	}
+
+	ret = PTR_ERR(retdesc);
+
+	/* FIXME: hack in the old code, is this really necessary? */
+	if (ret == -EINVAL)
+		retdesc = ERR_PTR(-EPROBE_DEFER);
+
+	/* This happens if the GPIO driver is not yet probed, let's defer */
+	if (ret == -ENOENT)
+		retdesc = ERR_PTR(-EPROBE_DEFER);
+
+	if (PTR_ERR(retdesc) != -EPROBE_DEFER)
+		dev_err(dev, "error trying to get descriptor: %d\n", ret);
+
+	return retdesc;
+}
+
+static int i2c_gpio_probe(struct platform_device *pdev)
+{
+	struct i2c_gpio_private_data *priv;
+	struct i2c_gpio_platform_data *pdata;
+	struct i2c_algo_bit_data *bit_data;
+	struct i2c_adapter *adap;
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node;
+	enum gpiod_flags gflags;
+	int ret;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	adap = &priv->adap;
+	bit_data = &priv->bit_data;
+	pdata = &priv->pdata;
+
+	if (np) {
+		of_i2c_gpio_get_props(np, pdata);
+	} else {
+		/*
+		 * If all platform data settings are zero it is OK
+		 * to not provide any platform data from the board.
+		 */
+		if (dev_get_platdata(dev))
+			memcpy(pdata, dev_get_platdata(dev), sizeof(*pdata));
+	}
+
+	/*
+	 * First get the GPIO pins; if it fails, we'll defer the probe.
+	 * If the SCL/SDA lines are marked "open drain" by platform data or
+	 * device tree then this means that something outside of our control is
+	 * marking these lines to be handled as open drain, and we should just
+	 * handle them as we handle any other output. Else we enforce open
+	 * drain as this is required for an I2C bus.
+	 */
+	if (pdata->sda_is_open_drain)
+		gflags = GPIOD_OUT_HIGH;
+	else
+		gflags = GPIOD_OUT_HIGH_OPEN_DRAIN;
+	priv->sda = i2c_gpio_get_desc(dev, "sda", 0, gflags);
+	if (IS_ERR(priv->sda))
+		return PTR_ERR(priv->sda);
+
+	if (pdata->scl_is_open_drain)
+		gflags = GPIOD_OUT_HIGH;
+	else
+		gflags = GPIOD_OUT_HIGH_OPEN_DRAIN;
+	priv->scl = i2c_gpio_get_desc(dev, "scl", 1, gflags);
+	if (IS_ERR(priv->scl))
+		return PTR_ERR(priv->scl);
+
+	if (gpiod_cansleep(priv->sda) || gpiod_cansleep(priv->scl))
+		dev_warn(dev, "Slow GPIO pins might wreak havoc into I2C/SMBus bus timing");
+	else
+		bit_data->can_do_atomic = true;
+
+	bit_data->setsda = i2c_gpio_setsda_val;
+	bit_data->setscl = i2c_gpio_setscl_val;
+
+	if (!pdata->scl_is_output_only)
+		bit_data->getscl = i2c_gpio_getscl;
+	bit_data->getsda = i2c_gpio_getsda;
+
+	if (pdata->udelay)
+		bit_data->udelay = pdata->udelay;
+	else if (pdata->scl_is_output_only)
+		bit_data->udelay = 50;			/* 10 kHz */
+	else
+		bit_data->udelay = 5;			/* 100 kHz */
+
+	if (pdata->timeout)
+		bit_data->timeout = pdata->timeout;
+	else
+		bit_data->timeout = HZ / 10;		/* 100 ms */
+
+	bit_data->data = priv;
+
+	adap->owner = THIS_MODULE;
+	if (np)
+		strscpy(adap->name, dev_name(dev), sizeof(adap->name));
+	else
+		snprintf(adap->name, sizeof(adap->name), "i2c-gpio%d", pdev->id);
+
+	adap->algo_data = bit_data;
+	adap->class = I2C_CLASS_HWMON | I2C_CLASS_SPD;
+	adap->dev.parent = dev;
+	adap->dev.of_node = np;
+
+	if (pdev->id != PLATFORM_DEVID_NONE || !pdev->dev.of_node ||
+	    of_property_read_u32(pdev->dev.of_node, "reg", &adap->nr))
+		adap->nr = pdev->id;
+	ret = i2c_bit_add_numbered_bus(adap);
+	if (ret)
+		return ret;
+
+	platform_set_drvdata(pdev, priv);
+
+	/*
+	 * FIXME: using global GPIO numbers is not helpful. If/when we
+	 * get accessors to get the actual name of the GPIO line,
+	 * from the descriptor, then provide that instead.
+	 */
+	dev_info(dev, "using lines %u (SDA) and %u (SCL%s)\n",
+		 desc_to_gpio(priv->sda), desc_to_gpio(priv->scl),
+		 pdata->scl_is_output_only
+		 ? ", no clock stretching" : "");
+
+	i2c_gpio_fault_injector_init(pdev);
+
+	return 0;
+}
+
+static int i2c_gpio_remove(struct platform_device *pdev)
+{
+	struct i2c_gpio_private_data *priv;
+	struct i2c_adapter *adap;
+
+	i2c_gpio_fault_injector_exit(pdev);
+
+	priv = platform_get_drvdata(pdev);
+	adap = &priv->adap;
+
+	i2c_del_adapter(adap);
+
+	return 0;
+}
+
+#if defined(CONFIG_OF)
+static const struct of_device_id i2c_gpio_dt_ids[] = {
+	{ .compatible = "i2c-gpio", },
+	{ /* sentinel */ }
+};
+
+MODULE_DEVICE_TABLE(of, i2c_gpio_dt_ids);
+#endif
+
+static struct platform_driver i2c_gpio_driver = {
+	.driver		= {
+		.name	= "i2c-gpio",
+		.of_match_table	= of_match_ptr(i2c_gpio_dt_ids),
+	},
+	.probe		= i2c_gpio_probe,
+	.remove		= i2c_gpio_remove,
+};
+
+static int __init i2c_gpio_init(void)
+{
+	int ret;
+
+	ret = platform_driver_register(&i2c_gpio_driver);
+	if (ret)
+		printk(KERN_ERR "i2c-gpio: probe failed: %d\n", ret);
+
+	return ret;
+}
+subsys_initcall(i2c_gpio_init);
+
+static void __exit i2c_gpio_exit(void)
+{
+	platform_driver_unregister(&i2c_gpio_driver);
+}
+module_exit(i2c_gpio_exit);
+
+MODULE_AUTHOR("Haavard Skinnemoen (Atmel)");
+MODULE_DESCRIPTION("Platform-independent bitbanging I2C driver (fix)");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:i2c-gpio");