diff options
author | David Brownell <david-b@pacbell.net> | 2006-01-08 13:34:19 -0800 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@suse.de> | 2006-01-13 16:29:54 -0800 |
commit | 8ae12a0d85987dc138f8c944cb78a92bf466cea0 (patch) | |
tree | ca032f25bb26f88cc35d68c6f8065143ce64a6a8 /include/linux/spi/spi.h | |
parent | 67daf5f11f06b9b15f8320de1d237ccc2e74fe43 (diff) |
[PATCH] spi: simple SPI framework
This is the core of a small SPI framework, implementing the model of a
queue of messages which complete asynchronously (with thin synchronous
wrappers on top).
- It's still less than 2KB of ".text" (ARM). If there's got to be a
mid-layer for something so simple, that's the right size budget. :)
- The guts use board-specific SPI device tables to build the driver
model tree. (Hardware probing is rarely an option.)
- This version of Kconfig includes no drivers. At this writing there
are two known master controller drivers (PXA/SSP, OMAP MicroWire)
and three protocol drivers (CS8415a, ADS7846, DataFlash) with LKML
mentions of other drivers in development.
- No userspace API. There are several implementations to compare.
Implement them like any other driver, and bind them with sysfs.
The changes from last version posted to LKML (on 11-Nov-2005) are minor,
and include:
- One bugfix (removes a FIXME), with the visible effect of making device
names be "spiB.C" where B is the bus number and C is the chipselect.
- The "caller provides DMA mappings" mechanism now has kerneldoc, for
DMA drivers that want to be fancy.
- Hey, the framework init can be subsys_init. Even though board init
logic fires earlier, at arch_init ... since the framework init is
for driver support, and the board init support uses static init.
- Various additional spec/doc clarifications based on discussions
with other folk. It adds a brief "thank you" at the end, for folk
who've helped nudge this framework into existence.
As I've said before, I think that "protocol tweaking" is the main support
that this driver framework will need to evolve.
From: Mark Underwood <basicmark@yahoo.com>
Update the SPI framework to remove a potential priority inversion case by
reverting to kmalloc if the pre-allocated DMA-safe buffer isn't available.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'include/linux/spi/spi.h')
-rw-r--r-- | include/linux/spi/spi.h | 542 |
1 files changed, 542 insertions, 0 deletions
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h new file mode 100644 index 00000000000..51a6769114d --- /dev/null +++ b/include/linux/spi/spi.h @@ -0,0 +1,542 @@ +/* + * Copyright (C) 2005 David Brownell + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. + */ + +#ifndef __LINUX_SPI_H +#define __LINUX_SPI_H + +/* + * INTERFACES between SPI master drivers and infrastructure + * (There's no SPI slave support for Linux yet...) + * + * A "struct device_driver" for an spi_device uses "spi_bus_type" and + * needs no special API wrappers (much like platform_bus). These drivers + * are bound to devices based on their names (much like platform_bus), + * and are available in dev->driver. + */ +extern struct bus_type spi_bus_type; + +/** + * struct spi_device - Master side proxy for an SPI slave device + * @dev: Driver model representation of the device. + * @master: SPI controller used with the device. + * @max_speed_hz: Maximum clock rate to be used with this chip + * (on this board); may be changed by the device's driver. + * @chip-select: Chipselect, distinguishing chips handled by "master". + * @mode: The spi mode defines how data is clocked out and in. + * This may be changed by the device's driver. + * @bits_per_word: Data transfers involve one or more words; word sizes + * like eight or 12 bits are common. In-memory wordsizes are + * powers of two bytes (e.g. 20 bit samples use 32 bits). + * This may be changed by the device's driver. + * @irq: Negative, or the number passed to request_irq() to receive + * interrupts from this device. + * @controller_state: Controller's runtime state + * @controller_data: Static board-specific definitions for controller, such + * as FIFO initialization parameters; from board_info.controller_data + * + * An spi_device is used to interchange data between an SPI slave + * (usually a discrete chip) and CPU memory. + * + * In "dev", the platform_data is used to hold information about this + * device that's meaningful to the device's protocol driver, but not + * to its controller. One example might be an identifier for a chip + * variant with slightly different functionality. + */ +struct spi_device { + struct device dev; + struct spi_master *master; + u32 max_speed_hz; + u8 chip_select; + u8 mode; +#define SPI_CPHA 0x01 /* clock phase */ +#define SPI_CPOL 0x02 /* clock polarity */ +#define SPI_MODE_0 (0|0) +#define SPI_MODE_1 (0|SPI_CPHA) +#define SPI_MODE_2 (SPI_CPOL|0) +#define SPI_MODE_3 (SPI_CPOL|SPI_CPHA) +#define SPI_CS_HIGH 0x04 /* chipselect active high? */ + u8 bits_per_word; + int irq; + void *controller_state; + const void *controller_data; + const char *modalias; + + // likely need more hooks for more protocol options affecting how + // the controller talks to its chips, like: + // - bit order (default is wordwise msb-first) + // - memory packing (12 bit samples into low bits, others zeroed) + // - priority + // - chipselect delays + // - ... +}; + +static inline struct spi_device *to_spi_device(struct device *dev) +{ + return container_of(dev, struct spi_device, dev); +} + +/* most drivers won't need to care about device refcounting */ +static inline struct spi_device *spi_dev_get(struct spi_device *spi) +{ + return (spi && get_device(&spi->dev)) ? spi : NULL; +} + +static inline void spi_dev_put(struct spi_device *spi) +{ + if (spi) + put_device(&spi->dev); +} + +/* ctldata is for the bus_master driver's runtime state */ +static inline void *spi_get_ctldata(struct spi_device *spi) +{ + return spi->controller_state; +} + +static inline void spi_set_ctldata(struct spi_device *spi, void *state) +{ + spi->controller_state = state; +} + + +struct spi_message; + + +/** + * struct spi_master - interface to SPI master controller + * @cdev: class interface to this driver + * @bus_num: board-specific (and often SOC-specific) identifier for a + * given SPI controller. + * @num_chipselects: chipselects are used to distinguish individual + * SPI slaves, and are numbered from zero to num_chipselects. + * each slave has a chipselect signal, but it's common that not + * every chipselect is connected to a slave. + * @setup: updates the device mode and clocking records used by a + * device's SPI controller; protocol code may call this. + * @transfer: adds a message to the controller's transfer queue. + * @cleanup: frees controller-specific state + * + * Each SPI master controller can communicate with one or more spi_device + * children. These make a small bus, sharing MOSI, MISO and SCK signals + * but not chip select signals. Each device may be configured to use a + * different clock rate, since those shared signals are ignored unless + * the chip is selected. + * + * The driver for an SPI controller manages access to those devices through + * a queue of spi_message transactions, copyin data between CPU memory and + * an SPI slave device). For each such message it queues, it calls the + * message's completion function when the transaction completes. + */ +struct spi_master { + struct class_device cdev; + + /* other than zero (== assign one dynamically), bus_num is fully + * board-specific. usually that simplifies to being SOC-specific. + * example: one SOC has three SPI controllers, numbered 1..3, + * and one board's schematics might show it using SPI-2. software + * would normally use bus_num=2 for that controller. + */ + u16 bus_num; + + /* chipselects will be integral to many controllers; some others + * might use board-specific GPIOs. + */ + u16 num_chipselect; + + /* setup mode and clock, etc (spi driver may call many times) */ + int (*setup)(struct spi_device *spi); + + /* bidirectional bulk transfers + * + * + The transfer() method may not sleep; its main role is + * just to add the message to the queue. + * + For now there's no remove-from-queue operation, or + * any other request management + * + To a given spi_device, message queueing is pure fifo + * + * + The master's main job is to process its message queue, + * selecting a chip then transferring data + * + If there are multiple spi_device children, the i/o queue + * arbitration algorithm is unspecified (round robin, fifo, + * priority, reservations, preemption, etc) + * + * + Chipselect stays active during the entire message + * (unless modified by spi_transfer.cs_change != 0). + * + The message transfers use clock and SPI mode parameters + * previously established by setup() for this device + */ + int (*transfer)(struct spi_device *spi, + struct spi_message *mesg); + + /* called on release() to free memory provided by spi_master */ + void (*cleanup)(const struct spi_device *spi); +}; + +/* the spi driver core manages memory for the spi_master classdev */ +extern struct spi_master * +spi_alloc_master(struct device *host, unsigned size); + +extern int spi_register_master(struct spi_master *master); +extern void spi_unregister_master(struct spi_master *master); + +extern struct spi_master *spi_busnum_to_master(u16 busnum); + +/*---------------------------------------------------------------------------*/ + +/* + * I/O INTERFACE between SPI controller and protocol drivers + * + * Protocol drivers use a queue of spi_messages, each transferring data + * between the controller and memory buffers. + * + * The spi_messages themselves consist of a series of read+write transfer + * segments. Those segments always read the same number of bits as they + * write; but one or the other is easily ignored by passing a null buffer + * pointer. (This is unlike most types of I/O API, because SPI hardware + * is full duplex.) + * + * NOTE: Allocation of spi_transfer and spi_message memory is entirely + * up to the protocol driver, which guarantees the integrity of both (as + * well as the data buffers) for as long as the message is queued. + */ + +/** + * struct spi_transfer - a read/write buffer pair + * @tx_buf: data to be written (dma-safe address), or NULL + * @rx_buf: data to be read (dma-safe address), or NULL + * @tx_dma: DMA address of buffer, if spi_message.is_dma_mapped + * @rx_dma: DMA address of buffer, if spi_message.is_dma_mapped + * @len: size of rx and tx buffers (in bytes) + * @cs_change: affects chipselect after this transfer completes + * @delay_usecs: microseconds to delay after this transfer before + * (optionally) changing the chipselect status, then starting + * the next transfer or completing this spi_message. + * + * SPI transfers always write the same number of bytes as they read. + * Protocol drivers should always provide rx_buf and/or tx_buf. + * In some cases, they may also want to provide DMA addresses for + * the data being transferred; that may reduce overhead, when the + * underlying driver uses dma. + * + * All SPI transfers start with the relevant chipselect active. Drivers + * can change behavior of the chipselect after the transfer finishes + * (including any mandatory delay). The normal behavior is to leave it + * selected, except for the last transfer in a message. Setting cs_change + * allows two additional behavior options: + * + * (i) If the transfer isn't the last one in the message, this flag is + * used to make the chipselect briefly go inactive in the middle of the + * message. Toggling chipselect in this way may be needed to terminate + * a chip command, letting a single spi_message perform all of group of + * chip transactions together. + * + * (ii) When the transfer is the last one in the message, the chip may + * stay selected until the next transfer. This is purely a performance + * hint; the controller driver may need to select a different device + * for the next message. + */ +struct spi_transfer { + /* it's ok if tx_buf == rx_buf (right?) + * for MicroWire, one buffer must be null + * buffers must work with dma_*map_single() calls + */ + const void *tx_buf; + void *rx_buf; + unsigned len; + + dma_addr_t tx_dma; + dma_addr_t rx_dma; + + unsigned cs_change:1; + u16 delay_usecs; +}; + +/** + * struct spi_message - one multi-segment SPI transaction + * @transfers: the segements of the transaction + * @n_transfer: how many segments + * @spi: SPI device to which the transaction is queued + * @is_dma_mapped: if true, the caller provided both dma and cpu virtual + * addresses for each transfer buffer + * @complete: called to report transaction completions + * @context: the argument to complete() when it's called + * @actual_length: how many bytes were transferd + * @status: zero for success, else negative errno + * @queue: for use by whichever driver currently owns the message + * @state: for use by whichever driver currently owns the message + */ +struct spi_message { + struct spi_transfer *transfers; + unsigned n_transfer; + + struct spi_device *spi; + + unsigned is_dma_mapped:1; + + /* REVISIT: we might want a flag affecting the behavior of the + * last transfer ... allowing things like "read 16 bit length L" + * immediately followed by "read L bytes". Basically imposing + * a specific message scheduling algorithm. + * + * Some controller drivers (message-at-a-time queue processing) + * could provide that as their default scheduling algorithm. But + * others (with multi-message pipelines) would need a flag to + * tell them about such special cases. + */ + + /* completion is reported through a callback */ + void FASTCALL((*complete)(void *context)); + void *context; + unsigned actual_length; + int status; + + /* for optional use by whatever driver currently owns the + * spi_message ... between calls to spi_async and then later + * complete(), that's the spi_master controller driver. + */ + struct list_head queue; + void *state; +}; + +/** + * spi_setup -- setup SPI mode and clock rate + * @spi: the device whose settings are being modified + * + * SPI protocol drivers may need to update the transfer mode if the + * device doesn't work with the mode 0 default. They may likewise need + * to update clock rates or word sizes from initial values. This function + * changes those settings, and must be called from a context that can sleep. + */ +static inline int +spi_setup(struct spi_device *spi) +{ + return spi->master->setup(spi); +} + + +/** + * spi_async -- asynchronous SPI transfer + * @spi: device with which data will be exchanged + * @message: describes the data transfers, including completion callback + * + * This call may be used in_irq and other contexts which can't sleep, + * as well as from task contexts which can sleep. + * + * The completion callback is invoked in a context which can't sleep. + * Before that invocation, the value of message->status is undefined. + * When the callback is issued, message->status holds either zero (to + * indicate complete success) or a negative error code. + * + * Note that although all messages to a spi_device are handled in + * FIFO order, messages may go to different devices in other orders. + * Some device might be higher priority, or have various "hard" access + * time requirements, for example. + */ +static inline int +spi_async(struct spi_device *spi, struct spi_message *message) +{ + message->spi = spi; + return spi->master->transfer(spi, message); +} + +/*---------------------------------------------------------------------------*/ + +/* All these synchronous SPI transfer routines are utilities layered + * over the core async transfer primitive. Here, "synchronous" means + * they will sleep uninterruptibly until the async transfer completes. + */ + +extern int spi_sync(struct spi_device *spi, struct spi_message *message); + +/** + * spi_write - SPI synchronous write + * @spi: device to which data will be written + * @buf: data buffer + * @len: data buffer size + * + * This writes the buffer and returns zero or a negative error code. + * Callable only from contexts that can sleep. + */ +static inline int +spi_write(struct spi_device *spi, const u8 *buf, size_t len) +{ + struct spi_transfer t = { + .tx_buf = buf, + .rx_buf = NULL, + .len = len, + .cs_change = 0, + }; + struct spi_message m = { + .transfers = &t, + .n_transfer = 1, + }; + + return spi_sync(spi, &m); +} + +/** + * spi_read - SPI synchronous read + * @spi: device from which data will be read + * @buf: data buffer + * @len: data buffer size + * + * This writes the buffer and returns zero or a negative error code. + * Callable only from contexts that can sleep. + */ +static inline int +spi_read(struct spi_device *spi, u8 *buf, size_t len) +{ + struct spi_transfer t = { + .tx_buf = NULL, + .rx_buf = buf, + .len = len, + .cs_change = 0, + }; + struct spi_message m = { + .transfers = &t, + .n_transfer = 1, + }; + + return spi_sync(spi, &m); +} + +extern int spi_write_then_read(struct spi_device *spi, + const u8 *txbuf, unsigned n_tx, + u8 *rxbuf, unsigned n_rx); + +/** + * spi_w8r8 - SPI synchronous 8 bit write followed by 8 bit read + * @spi: device with which data will be exchanged + * @cmd: command to be written before data is read back + * + * This returns the (unsigned) eight bit number returned by the + * device, or else a negative error code. Callable only from + * contexts that can sleep. + */ +static inline ssize_t spi_w8r8(struct spi_device *spi, u8 cmd) +{ + ssize_t status; + u8 result; + + status = spi_write_then_read(spi, &cmd, 1, &result, 1); + + /* return negative errno or unsigned value */ + return (status < 0) ? status : result; +} + +/** + * spi_w8r16 - SPI synchronous 8 bit write followed by 16 bit read + * @spi: device with which data will be exchanged + * @cmd: command to be written before data is read back + * + * This returns the (unsigned) sixteen bit number returned by the + * device, or else a negative error code. Callable only from + * contexts that can sleep. + * + * The number is returned in wire-order, which is at least sometimes + * big-endian. + */ +static inline ssize_t spi_w8r16(struct spi_device *spi, u8 cmd) +{ + ssize_t status; + u16 result; + + status = spi_write_then_read(spi, &cmd, 1, (u8 *) &result, 2); + + /* return negative errno or unsigned value */ + return (status < 0) ? status : result; +} + +/*---------------------------------------------------------------------------*/ + +/* + * INTERFACE between board init code and SPI infrastructure. + * + * No SPI driver ever sees these SPI device table segments, but + * it's how the SPI core (or adapters that get hotplugged) grows + * the driver model tree. + * + * As a rule, SPI devices can't be probed. Instead, board init code + * provides a table listing the devices which are present, with enough + * information to bind and set up the device's driver. There's basic + * support for nonstatic configurations too; enough to handle adding + * parport adapters, or microcontrollers acting as USB-to-SPI bridges. + */ + +/* board-specific information about each SPI device */ +struct spi_board_info { + /* the device name and module name are coupled, like platform_bus; + * "modalias" is normally the driver name. + * + * platform_data goes to spi_device.dev.platform_data, + * controller_data goes to spi_device.platform_data, + * irq is copied too + */ + char modalias[KOBJ_NAME_LEN]; + const void *platform_data; + const void *controller_data; + int irq; + + /* slower signaling on noisy or low voltage boards */ + u32 max_speed_hz; + + + /* bus_num is board specific and matches the bus_num of some + * spi_master that will probably be registered later. + * + * chip_select reflects how this chip is wired to that master; + * it's less than num_chipselect. + */ + u16 bus_num; + u16 chip_select; + + /* ... may need additional spi_device chip config data here. + * avoid stuff protocol drivers can set; but include stuff + * needed to behave without being bound to a driver: + * - chipselect polarity + * - quirks like clock rate mattering when not selected + */ +}; + +#ifdef CONFIG_SPI +extern int +spi_register_board_info(struct spi_board_info const *info, unsigned n); +#else +/* board init code may ignore whether SPI is configured or not */ +static inline int +spi_register_board_info(struct spi_board_info const *info, unsigned n) + { return 0; } +#endif + + +/* If you're hotplugging an adapter with devices (parport, usb, etc) + * use spi_new_device() to describe each device. You can also call + * spi_unregister_device() to get start making that device vanish, + * but normally that would be handled by spi_unregister_master(). + */ +extern struct spi_device * +spi_new_device(struct spi_master *, struct spi_board_info *); + +static inline void +spi_unregister_device(struct spi_device *spi) +{ + if (spi) + device_unregister(&spi->dev); +} + +#endif /* __LINUX_SPI_H */ |