1 files changed, 415 insertions, 0 deletions
diff --git a/drivers/i2c/i2c-core-of-prober.c b/drivers/i2c/i2c-core-of-prober.c
new file mode 100644
index 000000000000..0a66267e4836
--- /dev/null
+++ b/drivers/i2c/i2c-core-of-prober.c
@@ -0,0 +1,415 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Linux I2C core OF component prober code
+ *
+ * Copyright (C) 2024 Google LLC
+ */
+
+#include <linux/cleanup.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/dev_printk.h>
+#include <linux/err.h>
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/i2c-of-prober.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/regulator/consumer.h>
+#include <linux/slab.h>
+#include <linux/stddef.h>
+
+/*
+ * Some devices, such as Google Hana Chromebooks, are produced by multiple
+ * vendors each using their preferred components. Such components are all
+ * in the device tree. Instead of having all of them enabled and having each
+ * driver separately try and probe its device while fighting over shared
+ * resources, they can be marked as "fail-needs-probe" and have a prober
+ * figure out which one is actually used beforehand.
+ *
+ * This prober assumes such drop-in parts are on the same I2C bus, have
+ * non-conflicting addresses, and can be directly probed by seeing which
+ * address responds.
+ *
+ * TODO:
+ * - Support I2C muxes
+ */
+
+static struct device_node *i2c_of_probe_get_i2c_node(struct device *dev, const char *type)
+{
+	struct device_node *node __free(device_node) = of_find_node_by_name(NULL, type);
+	if (!node) {
+		dev_err(dev, "Could not find %s device node\n", type);
+		return NULL;
+	}
+
+	struct device_node *i2c_node __free(device_node) = of_get_parent(node);
+	if (!of_node_name_eq(i2c_node, "i2c")) {
+		dev_err(dev, "%s device isn't on I2C bus\n", type);
+		return NULL;
+	}
+
+	if (!of_device_is_available(i2c_node)) {
+		dev_err(dev, "I2C controller not available\n");
+		return NULL;
+	}
+
+	return no_free_ptr(i2c_node);
+}
+
+static int i2c_of_probe_enable_node(struct device *dev, struct device_node *node)
+{
+	int ret;
+
+	dev_dbg(dev, "Enabling %pOF\n", node);
+
+	struct of_changeset *ocs __free(kfree) = kzalloc(sizeof(*ocs), GFP_KERNEL);
+	if (!ocs)
+		return -ENOMEM;
+
+	of_changeset_init(ocs);
+	ret = of_changeset_update_prop_string(ocs, node, "status", "okay");
+	if (ret)
+		return ret;
+
+	ret = of_changeset_apply(ocs);
+	if (ret) {
+		/* ocs needs to be explicitly cleaned up before being freed. */
+		of_changeset_destroy(ocs);
+	} else {
+		/*
+		 * ocs is intentionally kept around as it needs to
+		 * exist as long as the change is applied.
+		 */
+		void *ptr __always_unused = no_free_ptr(ocs);
+	}
+
+	return ret;
+}
+
+static const struct i2c_of_probe_ops i2c_of_probe_dummy_ops;
+
+/**
+ * i2c_of_probe_component() - probe for devices of "type" on the same i2c bus
+ * @dev: Pointer to the &struct device of the caller, only used for dev_printk() messages.
+ * @cfg: Pointer to the &struct i2c_of_probe_cfg containing callbacks and other options
+ *       for the prober.
+ * @ctx: Context data for callbacks.
+ *
+ * Probe for possible I2C components of the same "type" (&i2c_of_probe_cfg->type)
+ * on the same I2C bus that have their status marked as "fail-needs-probe".
+ *
+ * Assumes that across the entire device tree the only instances of nodes
+ * with "type" prefixed node names (not including the address portion) are
+ * the ones that need handling for second source components. In other words,
+ * if "type" is "touchscreen", then all device nodes named "touchscreen*"
+ * are the ones that need probing. There cannot be another "touchscreen*"
+ * node that is already enabled.
+ *
+ * Assumes that for each "type" of component, only one actually exists. In
+ * other words, only one matching and existing device will be enabled.
+ *
+ * Context: Process context only. Does non-atomic I2C transfers.
+ *          Should only be used from a driver probe function, as the function
+ *          can return -EPROBE_DEFER if the I2C adapter or other resources
+ *          are unavailable.
+ * Return: 0 on success or no-op, error code otherwise.
+ *         A no-op can happen when it seems like the device tree already
+ *         has components of the type to be probed already enabled. This
+ *         can happen when the device tree had not been updated to mark
+ *         the status of the to-be-probed components as "fail-needs-probe".
+ *         Or this function was already run with the same parameters and
+ *         succeeded in enabling a component. The latter could happen if
+ *         the user had multiple types of components to probe, and one of
+ *         them down the list caused a deferred probe. This is expected
+ *         behavior.
+ */
+int i2c_of_probe_component(struct device *dev, const struct i2c_of_probe_cfg *cfg, void *ctx)
+{
+	const struct i2c_of_probe_ops *ops;
+	const char *type;
+	struct i2c_adapter *i2c;
+	int ret;
+
+	ops = cfg->ops ?: &i2c_of_probe_dummy_ops;
+	type = cfg->type;
+
+	struct device_node *i2c_node __free(device_node) = i2c_of_probe_get_i2c_node(dev, type);
+	if (!i2c_node)
+		return -ENODEV;
+
+	/*
+	 * If any devices of the given "type" are already enabled then this function is a no-op.
+	 * Either the device tree hasn't been modified to work with this probe function, or the
+	 * function had already run before and enabled some component.
+	 */
+	for_each_child_of_node_with_prefix(i2c_node, node, type)
+		if (of_device_is_available(node))
+			return 0;
+
+	i2c = of_get_i2c_adapter_by_node(i2c_node);
+	if (!i2c)
+		return dev_err_probe(dev, -EPROBE_DEFER, "Couldn't get I2C adapter\n");
+
+	/* Grab and enable resources */
+	ret = 0;
+	if (ops->enable)
+		ret = ops->enable(dev, i2c_node, ctx);
+	if (ret)
+		goto out_put_i2c_adapter;
+
+	for_each_child_of_node_with_prefix(i2c_node, node, type) {
+		union i2c_smbus_data data;
+		u32 addr;
+
+		if (of_property_read_u32(node, "reg", &addr))
+			continue;
+		if (i2c_smbus_xfer(i2c, addr, 0, I2C_SMBUS_READ, 0, I2C_SMBUS_BYTE, &data) < 0)
+			continue;
+
+		/* Found a device that is responding */
+		if (ops->cleanup_early)
+			ops->cleanup_early(dev, ctx);
+		ret = i2c_of_probe_enable_node(dev, node);
+		break;
+	}
+
+	if (ops->cleanup)
+		ops->cleanup(dev, ctx);
+out_put_i2c_adapter:
+	i2c_put_adapter(i2c);
+
+	return ret;
+}
+EXPORT_SYMBOL_NS_GPL(i2c_of_probe_component, "I2C_OF_PROBER");
+
+static int i2c_of_probe_simple_get_supply(struct device *dev, struct device_node *node,
+					  struct i2c_of_probe_simple_ctx *ctx)
+{
+	const char *supply_name;
+	struct regulator *supply;
+
+	/*
+	 * It's entirely possible for the component's device node to not have the
+	 * regulator supplies. While it does not make sense from a hardware perspective,
+	 * the supplies could be always on or otherwise not modeled in the device tree,
+	 * but the device would still work.
+	 */
+	supply_name = ctx->opts->supply_name;
+	if (!supply_name)
+		return 0;
+
+	supply = of_regulator_get_optional(dev, node, supply_name);
+	if (IS_ERR(supply)) {
+		return dev_err_probe(dev, PTR_ERR(supply),
+				     "Failed to get regulator supply \"%s\" from %pOF\n",
+				     supply_name, node);
+	}
+
+	ctx->supply = supply;
+
+	return 0;
+}
+
+static void i2c_of_probe_simple_put_supply(struct i2c_of_probe_simple_ctx *ctx)
+{
+	regulator_put(ctx->supply);
+	ctx->supply = NULL;
+}
+
+static int i2c_of_probe_simple_enable_regulator(struct device *dev, struct i2c_of_probe_simple_ctx *ctx)
+{
+	int ret;
+
+	if (!ctx->supply)
+		return 0;
+
+	dev_dbg(dev, "Enabling regulator supply \"%s\"\n", ctx->opts->supply_name);
+
+	ret = regulator_enable(ctx->supply);
+	if (ret)
+		return ret;
+
+	if (ctx->opts->post_power_on_delay_ms)
+		msleep(ctx->opts->post_power_on_delay_ms);
+
+	return 0;
+}
+
+static void i2c_of_probe_simple_disable_regulator(struct device *dev, struct i2c_of_probe_simple_ctx *ctx)
+{
+	if (!ctx->supply)
+		return;
+
+	dev_dbg(dev, "Disabling regulator supply \"%s\"\n", ctx->opts->supply_name);
+
+	regulator_disable(ctx->supply);
+}
+
+static int i2c_of_probe_simple_get_gpiod(struct device *dev, struct device_node *node,
+					 struct i2c_of_probe_simple_ctx *ctx)
+{
+	struct fwnode_handle *fwnode = of_fwnode_handle(node);
+	struct gpio_desc *gpiod;
+	const char *con_id;
+
+	/* NULL signals no GPIO needed */
+	if (!ctx->opts->gpio_name)
+		return 0;
+
+	/* An empty string signals an unnamed GPIO */
+	if (!ctx->opts->gpio_name[0])
+		con_id = NULL;
+	else
+		con_id = ctx->opts->gpio_name;
+
+	gpiod = fwnode_gpiod_get_index(fwnode, con_id, 0, GPIOD_ASIS, "i2c-of-prober");
+	if (IS_ERR(gpiod))
+		return PTR_ERR(gpiod);
+
+	ctx->gpiod = gpiod;
+
+	return 0;
+}
+
+static void i2c_of_probe_simple_put_gpiod(struct i2c_of_probe_simple_ctx *ctx)
+{
+	gpiod_put(ctx->gpiod);
+	ctx->gpiod = NULL;
+}
+
+static int i2c_of_probe_simple_set_gpio(struct device *dev, struct i2c_of_probe_simple_ctx *ctx)
+{
+	int ret;
+
+	if (!ctx->gpiod)
+		return 0;
+
+	dev_dbg(dev, "Configuring GPIO\n");
+
+	ret = gpiod_direction_output(ctx->gpiod, ctx->opts->gpio_assert_to_enable);
+	if (ret)
+		return ret;
+
+	if (ctx->opts->post_gpio_config_delay_ms)
+		msleep(ctx->opts->post_gpio_config_delay_ms);
+
+	return 0;
+}
+
+static void i2c_of_probe_simple_disable_gpio(struct device *dev, struct i2c_of_probe_simple_ctx *ctx)
+{
+	gpiod_set_value(ctx->gpiod, !ctx->opts->gpio_assert_to_enable);
+}
+
+/**
+ * i2c_of_probe_simple_enable - Simple helper for I2C OF prober to get and enable resources
+ * @dev: Pointer to the &struct device of the caller, only used for dev_printk() messages
+ * @bus_node: Pointer to the &struct device_node of the I2C adapter.
+ * @data: Pointer to &struct i2c_of_probe_simple_ctx helper context.
+ *
+ * If &i2c_of_probe_simple_opts->supply_name is given, request the named regulator supply.
+ * If &i2c_of_probe_simple_opts->gpio_name is given, request the named GPIO. Or if it is
+ * the empty string, request the unnamed GPIO.
+ * If a regulator supply was found, enable that regulator.
+ * If a GPIO line was found, configure the GPIO line to output and set value
+ * according to given options.
+ *
+ * Return: %0 on success or no-op, or a negative error number on failure.
+ */
+int i2c_of_probe_simple_enable(struct device *dev, struct device_node *bus_node, void *data)
+{
+	struct i2c_of_probe_simple_ctx *ctx = data;
+	struct device_node *node;
+	const char *compat;
+	int ret;
+
+	dev_dbg(dev, "Requesting resources for components under I2C bus %pOF\n", bus_node);
+
+	if (!ctx || !ctx->opts)
+		return -EINVAL;
+
+	compat = ctx->opts->res_node_compatible;
+	if (!compat)
+		return -EINVAL;
+
+	node = of_get_compatible_child(bus_node, compat);
+	if (!node)
+		return dev_err_probe(dev, -ENODEV, "No device compatible with \"%s\" found\n",
+				     compat);
+
+	ret = i2c_of_probe_simple_get_supply(dev, node, ctx);
+	if (ret)
+		goto out_put_node;
+
+	ret = i2c_of_probe_simple_get_gpiod(dev, node, ctx);
+	if (ret)
+		goto out_put_supply;
+
+	ret = i2c_of_probe_simple_enable_regulator(dev, ctx);
+	if (ret)
+		goto out_put_gpiod;
+
+	ret = i2c_of_probe_simple_set_gpio(dev, ctx);
+	if (ret)
+		goto out_disable_regulator;
+
+	return 0;
+
+out_disable_regulator:
+	i2c_of_probe_simple_disable_regulator(dev, ctx);
+out_put_gpiod:
+	i2c_of_probe_simple_put_gpiod(ctx);
+out_put_supply:
+	i2c_of_probe_simple_put_supply(ctx);
+out_put_node:
+	of_node_put(node);
+	return ret;
+}
+EXPORT_SYMBOL_NS_GPL(i2c_of_probe_simple_enable, "I2C_OF_PROBER");
+
+/**
+ * i2c_of_probe_simple_cleanup_early - \
+ *	Simple helper for I2C OF prober to release GPIOs before component is enabled
+ * @dev: Pointer to the &struct device of the caller; unused.
+ * @data: Pointer to &struct i2c_of_probe_simple_ctx helper context.
+ *
+ * GPIO descriptors are exclusive and have to be released before the
+ * actual driver probes so that the latter can acquire them.
+ */
+void i2c_of_probe_simple_cleanup_early(struct device *dev, void *data)
+{
+	struct i2c_of_probe_simple_ctx *ctx = data;
+
+	i2c_of_probe_simple_put_gpiod(ctx);
+}
+EXPORT_SYMBOL_NS_GPL(i2c_of_probe_simple_cleanup_early, "I2C_OF_PROBER");
+
+/**
+ * i2c_of_probe_simple_cleanup - Clean up and release resources for I2C OF prober simple helpers
+ * @dev: Pointer to the &struct device of the caller, only used for dev_printk() messages
+ * @data: Pointer to &struct i2c_of_probe_simple_ctx helper context.
+ *
+ * * If a GPIO line was found and not yet released, set its value to the opposite of that
+ *   set in i2c_of_probe_simple_enable() and release it.
+ * * If a regulator supply was found, disable that regulator and release it.
+ */
+void i2c_of_probe_simple_cleanup(struct device *dev, void *data)
+{
+	struct i2c_of_probe_simple_ctx *ctx = data;
+
+	/* GPIO operations here are no-ops if i2c_of_probe_simple_cleanup_early was called. */
+	i2c_of_probe_simple_disable_gpio(dev, ctx);
+	i2c_of_probe_simple_put_gpiod(ctx);
+
+	i2c_of_probe_simple_disable_regulator(dev, ctx);
+	i2c_of_probe_simple_put_supply(ctx);
+}
+EXPORT_SYMBOL_NS_GPL(i2c_of_probe_simple_cleanup, "I2C_OF_PROBER");
+
+struct i2c_of_probe_ops i2c_of_probe_simple_ops = {
+	.enable = i2c_of_probe_simple_enable,
+	.cleanup_early = i2c_of_probe_simple_cleanup_early,
+	.cleanup = i2c_of_probe_simple_cleanup,
+};
+EXPORT_SYMBOL_NS_GPL(i2c_of_probe_simple_ops, "I2C_OF_PROBER");