diff --git a/MAINTAINERS b/MAINTAINERS index 85cdc618a51c..0f837aca327c 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -10702,6 +10702,14 @@ S: Maintained F: Documentation/devicetree/bindings/i2c/marvell,mv64xxx-i2c.yaml F: drivers/i2c/busses/i2c-mv64xxx.c +I2C OF COMPONENT PROBER +M: Chen-Yu Tsai +L: linux-i2c@vger.kernel.org +L: devicetree@vger.kernel.org +S: Maintained +F: drivers/i2c/i2c-core-of-prober.c +F: include/linux-i2c-of-prober.h + I2C OVER PARALLEL PORT M: Jean Delvare L: linux-i2c@vger.kernel.org diff --git a/drivers/i2c/Makefile b/drivers/i2c/Makefile index af95d6e7f004..d27de18de46f 100644 --- a/drivers/i2c/Makefile +++ b/drivers/i2c/Makefile @@ -9,6 +9,7 @@ i2c-core-y := i2c-core-base.o i2c-core-smbus.o i2c-core-$(CONFIG_ACPI) += i2c-core-acpi.o i2c-core-$(CONFIG_I2C_SLAVE) += i2c-core-slave.o i2c-core-$(CONFIG_OF) += i2c-core-of.o +i2c-core-$(CONFIG_OF_DYNAMIC) += i2c-core-of-prober.o obj-$(CONFIG_I2C_SMBUS) += i2c-smbus.o obj-$(CONFIG_I2C_CHARDEV) += i2c-dev.o diff --git a/drivers/i2c/i2c-core-of-prober.c b/drivers/i2c/i2c-core-of-prober.c new file mode 100644 index 000000000000..21f7a4769293 --- /dev/null +++ b/drivers/i2c/i2c-core-of-prober.c @@ -0,0 +1,183 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Linux I2C core OF component prober code + * + * Copyright (C) 2024 Google LLC + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +/* + * 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 handling common regulators. + * - Support handling common GPIOs. + * - 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); diff --git a/include/linux/i2c-of-prober.h b/include/linux/i2c-of-prober.h new file mode 100644 index 000000000000..e7e052ac9e48 --- /dev/null +++ b/include/linux/i2c-of-prober.h @@ -0,0 +1,75 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ +/* + * Definitions for the Linux I2C OF component prober + * + * Copyright (C) 2024 Google LLC + */ + +#ifndef _LINUX_I2C_OF_PROBER_H +#define _LINUX_I2C_OF_PROBER_H + +#include + +struct device; +struct device_node; + +/** + * struct i2c_of_probe_ops - I2C OF component prober callbacks + * + * A set of callbacks to be used by i2c_of_probe_component(). + * + * All callbacks are optional. Callbacks are called only once per run, and are + * used in the order they are defined in this structure. + * + * All callbacks that have return values shall return %0 on success, + * or a negative error number on failure. + * + * The @dev parameter passed to the callbacks is the same as @dev passed to + * i2c_of_probe_component(). It should only be used for dev_printk() calls + * and nothing else, especially not managed device resource (devres) APIs. + */ +struct i2c_of_probe_ops { + /** + * @enable: Retrieve and enable resources so that the components respond to probes. + * + * It is OK for this callback to return -EPROBE_DEFER since the intended use includes + * retrieving resources and enables them. Resources should be reverted to their initial + * state and released before returning if this fails. + */ + int (*enable)(struct device *dev, struct device_node *bus_node, void *data); + + /** + * @cleanup_early: Release exclusive resources prior to calling probe() on a + * detected component. + * + * Only called if a matching component is actually found. If none are found, + * resources that would have been released in this callback should be released in + * @free_resourcs_late instead. + */ + void (*cleanup_early)(struct device *dev, void *data); + + /** + * @cleanup: Opposite of @enable to balance refcounts and free resources after probing. + * + * Should check if resources were already freed by @cleanup_early. + */ + void (*cleanup)(struct device *dev, void *data); +}; + +/** + * struct i2c_of_probe_cfg - I2C OF component prober configuration + * @ops: Callbacks for the prober to use. + * @type: A string to match the device node name prefix to probe for. + */ +struct i2c_of_probe_cfg { + const struct i2c_of_probe_ops *ops; + const char *type; +}; + +#if IS_ENABLED(CONFIG_OF_DYNAMIC) + +int i2c_of_probe_component(struct device *dev, const struct i2c_of_probe_cfg *cfg, void *ctx); + +#endif /* IS_ENABLED(CONFIG_OF_DYNAMIC) */ + +#endif /* _LINUX_I2C_OF_PROBER_H */