drivers/acpi/acpi_platform.c. This limitation is only for the platform
devices, SPI and I2C devices are created automatically as described below.
+DMA support
+~~~~~~~~~~~
+DMA controllers enumerated via ACPI should be registered in the system to
+provide generic access to their resources. For example, a driver that would
+like to be accessible to slave devices via generic API call
+dma_request_slave_channel() must register itself at the end of the probe
+function like this:
+
+ err = devm_acpi_dma_controller_register(dev, xlate_func, dw);
+ /* Handle the error if it's not a case of !CONFIG_ACPI */
+
+and implement custom xlate function if needed (usually acpi_dma_simple_xlate()
+is enough) which converts the FixedDMA resource provided by struct
+acpi_dma_spec into the corresponding DMA channel. A piece of code for that case
+could look like:
+
+ #ifdef CONFIG_ACPI
+ struct filter_args {
+ /* Provide necessary information for the filter_func */
+ ...
+ };
+
+ static bool filter_func(struct dma_chan *chan, void *param)
+ {
+ /* Choose the proper channel */
+ ...
+ }
+
+ static struct dma_chan *xlate_func(struct acpi_dma_spec *dma_spec,
+ struct acpi_dma *adma)
+ {
+ dma_cap_mask_t cap;
+ struct filter_args args;
+
+ /* Prepare arguments for filter_func */
+ ...
+ return dma_request_channel(cap, filter_func, &args);
+ }
+ #else
+ static struct dma_chan *xlate_func(struct acpi_dma_spec *dma_spec,
+ struct acpi_dma *adma)
+ {
+ return NULL;
+ }
+ #endif
+
+dma_request_slave_channel() will call xlate_func() for each registered DMA
+controller. In the xlate function the proper channel must be chosen based on
+information in struct acpi_dma_spec and the properties of the controller
+provided by struct acpi_dma.
+
+Clients must call dma_request_slave_channel() with the string parameter that
+corresponds to a specific FixedDMA resource. By default "tx" means the first
+entry of the FixedDMA resource array, "rx" means the second entry. The table
+below shows a layout:
+
+ Device (I2C0)
+ {
+ ...
+ Method (_CRS, 0, NotSerialized)
+ {
+ Name (DBUF, ResourceTemplate ()
+ {
+ FixedDMA (0x0018, 0x0004, Width32bit, _Y48)
+ FixedDMA (0x0019, 0x0005, Width32bit, )
+ })
+ ...
+ }
+ }
+
+So, the FixedDMA with request line 0x0018 is "tx" and next one is "rx" in
+this example.
+
+In robust cases the client unfortunately needs to call
+acpi_dma_request_slave_chan_by_index() directly and therefore choose the
+specific FixedDMA resource by its index.
+
SPI serial bus support
~~~~~~~~~~~~~~~~~~~~~~
Slave devices behind SPI bus have SpiSerialBus resource attached to them.
--- /dev/null
+/*
+ * ACPI helpers for DMA request / controller
+ *
+ * Based on of-dma.c
+ *
+ * Copyright (C) 2013, Intel Corporation
+ * Author: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/list.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/acpi.h>
+#include <linux/acpi_dma.h>
+
+static LIST_HEAD(acpi_dma_list);
+static DEFINE_MUTEX(acpi_dma_lock);
+
+/**
+ * acpi_dma_controller_register - Register a DMA controller to ACPI DMA helpers
+ * @dev: struct device of DMA controller
+ * @acpi_dma_xlate: translation function which converts a dma specifier
+ * into a dma_chan structure
+ * @data pointer to controller specific data to be used by
+ * translation function
+ *
+ * Returns 0 on success or appropriate errno value on error.
+ *
+ * Allocated memory should be freed with appropriate acpi_dma_controller_free()
+ * call.
+ */
+int acpi_dma_controller_register(struct device *dev,
+ struct dma_chan *(*acpi_dma_xlate)
+ (struct acpi_dma_spec *, struct acpi_dma *),
+ void *data)
+{
+ struct acpi_device *adev;
+ struct acpi_dma *adma;
+
+ if (!dev || !acpi_dma_xlate)
+ return -EINVAL;
+
+ /* Check if the device was enumerated by ACPI */
+ if (!ACPI_HANDLE(dev))
+ return -EINVAL;
+
+ if (acpi_bus_get_device(ACPI_HANDLE(dev), &adev))
+ return -EINVAL;
+
+ adma = kzalloc(sizeof(*adma), GFP_KERNEL);
+ if (!adma)
+ return -ENOMEM;
+
+ adma->dev = dev;
+ adma->acpi_dma_xlate = acpi_dma_xlate;
+ adma->data = data;
+
+ /* Now queue acpi_dma controller structure in list */
+ mutex_lock(&acpi_dma_lock);
+ list_add_tail(&adma->dma_controllers, &acpi_dma_list);
+ mutex_unlock(&acpi_dma_lock);
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(acpi_dma_controller_register);
+
+/**
+ * acpi_dma_controller_free - Remove a DMA controller from ACPI DMA helpers list
+ * @dev: struct device of DMA controller
+ *
+ * Memory allocated by acpi_dma_controller_register() is freed here.
+ */
+int acpi_dma_controller_free(struct device *dev)
+{
+ struct acpi_dma *adma;
+
+ if (!dev)
+ return -EINVAL;
+
+ mutex_lock(&acpi_dma_lock);
+
+ list_for_each_entry(adma, &acpi_dma_list, dma_controllers)
+ if (adma->dev == dev) {
+ list_del(&adma->dma_controllers);
+ mutex_unlock(&acpi_dma_lock);
+ kfree(adma);
+ return 0;
+ }
+
+ mutex_unlock(&acpi_dma_lock);
+ return -ENODEV;
+}
+EXPORT_SYMBOL_GPL(acpi_dma_controller_free);
+
+static void devm_acpi_dma_release(struct device *dev, void *res)
+{
+ acpi_dma_controller_free(dev);
+}
+
+/**
+ * devm_acpi_dma_controller_register - resource managed acpi_dma_controller_register()
+ * @dev: device that is registering this DMA controller
+ * @acpi_dma_xlate: translation function
+ * @data pointer to controller specific data
+ *
+ * Managed acpi_dma_controller_register(). DMA controller registered by this
+ * function are automatically freed on driver detach. See
+ * acpi_dma_controller_register() for more information.
+ */
+int devm_acpi_dma_controller_register(struct device *dev,
+ struct dma_chan *(*acpi_dma_xlate)
+ (struct acpi_dma_spec *, struct acpi_dma *),
+ void *data)
+{
+ void *res;
+ int ret;
+
+ res = devres_alloc(devm_acpi_dma_release, 0, GFP_KERNEL);
+ if (!res)
+ return -ENOMEM;
+
+ ret = acpi_dma_controller_register(dev, acpi_dma_xlate, data);
+ if (ret) {
+ devres_free(res);
+ return ret;
+ }
+ devres_add(dev, res);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(devm_acpi_dma_controller_register);
+
+/**
+ * devm_acpi_dma_controller_free - resource managed acpi_dma_controller_free()
+ *
+ * Unregister a DMA controller registered with
+ * devm_acpi_dma_controller_register(). Normally this function will not need to
+ * be called and the resource management code will ensure that the resource is
+ * freed.
+ */
+void devm_acpi_dma_controller_free(struct device *dev)
+{
+ WARN_ON(devres_destroy(dev, devm_acpi_dma_release, NULL, NULL));
+}
+EXPORT_SYMBOL_GPL(devm_acpi_dma_controller_free);
+
+struct acpi_dma_parser_data {
+ struct acpi_dma_spec dma_spec;
+ size_t index;
+ size_t n;
+};
+
+/**
+ * acpi_dma_parse_fixed_dma - Parse FixedDMA ACPI resources to a DMA specifier
+ * @res: struct acpi_resource to get FixedDMA resources from
+ * @data: pointer to a helper struct acpi_dma_parser_data
+ */
+static int acpi_dma_parse_fixed_dma(struct acpi_resource *res, void *data)
+{
+ struct acpi_dma_parser_data *pdata = data;
+
+ if (res->type == ACPI_RESOURCE_TYPE_FIXED_DMA) {
+ struct acpi_resource_fixed_dma *dma = &res->data.fixed_dma;
+
+ if (pdata->n++ == pdata->index) {
+ pdata->dma_spec.chan_id = dma->channels;
+ pdata->dma_spec.slave_id = dma->request_lines;
+ }
+ }
+
+ /* Tell the ACPI core to skip this resource */
+ return 1;
+}
+
+/**
+ * acpi_dma_request_slave_chan_by_index - Get the DMA slave channel
+ * @dev: struct device to get DMA request from
+ * @index: index of FixedDMA descriptor for @dev
+ *
+ * Returns pointer to appropriate dma channel on success or NULL on error.
+ */
+struct dma_chan *acpi_dma_request_slave_chan_by_index(struct device *dev,
+ size_t index)
+{
+ struct acpi_dma_parser_data pdata;
+ struct acpi_dma_spec *dma_spec = &pdata.dma_spec;
+ struct list_head resource_list;
+ struct acpi_device *adev;
+ struct acpi_dma *adma;
+ struct dma_chan *chan = NULL;
+
+ /* Check if the device was enumerated by ACPI */
+ if (!dev || !ACPI_HANDLE(dev))
+ return NULL;
+
+ if (acpi_bus_get_device(ACPI_HANDLE(dev), &adev))
+ return NULL;
+
+ memset(&pdata, 0, sizeof(pdata));
+ pdata.index = index;
+
+ /* Initial values for the request line and channel */
+ dma_spec->chan_id = -1;
+ dma_spec->slave_id = -1;
+
+ INIT_LIST_HEAD(&resource_list);
+ acpi_dev_get_resources(adev, &resource_list,
+ acpi_dma_parse_fixed_dma, &pdata);
+ acpi_dev_free_resource_list(&resource_list);
+
+ if (dma_spec->slave_id < 0 || dma_spec->chan_id < 0)
+ return NULL;
+
+ mutex_lock(&acpi_dma_lock);
+
+ list_for_each_entry(adma, &acpi_dma_list, dma_controllers) {
+ dma_spec->dev = adma->dev;
+ chan = adma->acpi_dma_xlate(dma_spec, adma);
+ if (chan)
+ break;
+ }
+
+ mutex_unlock(&acpi_dma_lock);
+ return chan;
+}
+EXPORT_SYMBOL_GPL(acpi_dma_request_slave_chan_by_index);
+
+/**
+ * acpi_dma_request_slave_chan_by_name - Get the DMA slave channel
+ * @dev: struct device to get DMA request from
+ * @name: represents corresponding FixedDMA descriptor for @dev
+ *
+ * In order to support both Device Tree and ACPI in a single driver we
+ * translate the names "tx" and "rx" here based on the most common case where
+ * the first FixedDMA descriptor is TX and second is RX.
+ *
+ * Returns pointer to appropriate dma channel on success or NULL on error.
+ */
+struct dma_chan *acpi_dma_request_slave_chan_by_name(struct device *dev,
+ const char *name)
+{
+ size_t index;
+
+ if (!strcmp(name, "tx"))
+ index = 0;
+ else if (!strcmp(name, "rx"))
+ index = 1;
+ else
+ return NULL;
+
+ return acpi_dma_request_slave_chan_by_index(dev, index);
+}
+EXPORT_SYMBOL_GPL(acpi_dma_request_slave_chan_by_name);
+
+/**
+ * acpi_dma_simple_xlate - Simple ACPI DMA engine translation helper
+ * @dma_spec: pointer to ACPI DMA specifier
+ * @adma: pointer to ACPI DMA controller data
+ *
+ * A simple translation function for ACPI based devices. Passes &struct
+ * dma_spec to the DMA controller driver provided filter function. Returns
+ * pointer to the channel if found or %NULL otherwise.
+ */
+struct dma_chan *acpi_dma_simple_xlate(struct acpi_dma_spec *dma_spec,
+ struct acpi_dma *adma)
+{
+ struct acpi_dma_filter_info *info = adma->data;
+
+ if (!info || !info->filter_fn)
+ return NULL;
+
+ return dma_request_channel(info->dma_cap, info->filter_fn, dma_spec);
+}
+EXPORT_SYMBOL_GPL(acpi_dma_simple_xlate);
--- /dev/null
+/*
+ * ACPI helpers for DMA request / controller
+ *
+ * Based on of_dma.h
+ *
+ * Copyright (C) 2013, Intel Corporation
+ * Author: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef __LINUX_ACPI_DMA_H
+#define __LINUX_ACPI_DMA_H
+
+#include <linux/list.h>
+#include <linux/device.h>
+#include <linux/dmaengine.h>
+
+/**
+ * struct acpi_dma_spec - slave device DMA resources
+ * @chan_id: channel unique id
+ * @slave_id: request line unique id
+ * @dev: struct device of the DMA controller to be used in the filter
+ * function
+ */
+struct acpi_dma_spec {
+ int chan_id;
+ int slave_id;
+ struct device *dev;
+};
+
+/**
+ * struct acpi_dma - representation of the registered DMAC
+ * @dma_controllers: linked list node
+ * @dev: struct device of this controller
+ * @acpi_dma_xlate: callback function to find a suitable channel
+ * @data: private data used by a callback function
+ */
+struct acpi_dma {
+ struct list_head dma_controllers;
+ struct device *dev;
+ struct dma_chan *(*acpi_dma_xlate)
+ (struct acpi_dma_spec *, struct acpi_dma *);
+ void *data;
+};
+
+/* Used with acpi_dma_simple_xlate() */
+struct acpi_dma_filter_info {
+ dma_cap_mask_t dma_cap;
+ dma_filter_fn filter_fn;
+};
+
+#ifdef CONFIG_DMA_ACPI
+
+int acpi_dma_controller_register(struct device *dev,
+ struct dma_chan *(*acpi_dma_xlate)
+ (struct acpi_dma_spec *, struct acpi_dma *),
+ void *data);
+int acpi_dma_controller_free(struct device *dev);
+int devm_acpi_dma_controller_register(struct device *dev,
+ struct dma_chan *(*acpi_dma_xlate)
+ (struct acpi_dma_spec *, struct acpi_dma *),
+ void *data);
+void devm_acpi_dma_controller_free(struct device *dev);
+
+struct dma_chan *acpi_dma_request_slave_chan_by_index(struct device *dev,
+ size_t index);
+struct dma_chan *acpi_dma_request_slave_chan_by_name(struct device *dev,
+ const char *name);
+
+struct dma_chan *acpi_dma_simple_xlate(struct acpi_dma_spec *dma_spec,
+ struct acpi_dma *adma);
+#else
+
+static inline int acpi_dma_controller_register(struct device *dev,
+ struct dma_chan *(*acpi_dma_xlate)
+ (struct acpi_dma_spec *, struct acpi_dma *),
+ void *data)
+{
+ return -ENODEV;
+}
+static inline int acpi_dma_controller_free(struct device *dev)
+{
+ return -ENODEV;
+}
+static inline int devm_acpi_dma_controller_register(struct device *dev,
+ struct dma_chan *(*acpi_dma_xlate)
+ (struct acpi_dma_spec *, struct acpi_dma *),
+ void *data)
+{
+ return -ENODEV;
+}
+static inline void devm_acpi_dma_controller_free(struct device *dev)
+{
+}
+
+static inline struct dma_chan *acpi_dma_request_slave_chan_by_index(
+ struct device *dev, size_t index)
+{
+ return NULL;
+}
+static inline struct dma_chan *acpi_dma_request_slave_chan_by_name(
+ struct device *dev, const char *name)
+{
+ return NULL;
+}
+
+#define acpi_dma_simple_xlate NULL
+
+#endif
+
+#define acpi_dma_request_slave_channel acpi_dma_request_slave_chan_by_index
+
+#endif /* __LINUX_ACPI_DMA_H */
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