/*
* polling/bitbanging SPI master controller driver utilities
*
* 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.
*/
#include <linux/spinlock.h>
#include <linux/workqueue.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/errno.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/spi/spi.h>
#include <linux/spi/spi_bitbang.h>
#define SPI_BITBANG_CS_DELAY 100
/*----------------------------------------------------------------------*/
/*
* FIRST PART (OPTIONAL): word-at-a-time spi_transfer support.
* Use this for GPIO or shift-register level hardware APIs.
*
* spi_bitbang_cs is in spi_device->controller_state, which is unavailable
* to glue code. These bitbang setup() and cleanup() routines are always
* used, though maybe they're called from controller-aware code.
*
* chipselect() and friends may use spi_device->controller_data and
* controller registers as appropriate.
*
*
* NOTE: SPI controller pins can often be used as GPIO pins instead,
* which means you could use a bitbang driver either to get hardware
* working quickly, or testing for differences that aren't speed related.
*/
struct spi_bitbang_cs {
unsigned nsecs; /* (clock cycle time)/2 */
u32 (*txrx_word)(struct spi_device *spi, unsigned nsecs,
u32 word, u8 bits, unsigned flags);
unsigned (*txrx_bufs)(struct spi_device *,
u32 (*txrx_word)(
struct spi_device *spi,
unsigned nsecs,
u32 word, u8 bits,
unsigned flags),
unsigned, struct spi_transfer *,
unsigned);
};
static unsigned bitbang_txrx_8(
struct spi_device *spi,
u32 (*txrx_word)(struct spi_device *spi,
unsigned nsecs,
u32 word, u8 bits,
unsigned flags),
unsigned ns,
struct spi_transfer *t,
unsigned flags
) {
unsigned bits = t->bits_per_word;
unsigned count = t->len;
const u8 *tx = t->tx_buf;
u8 *rx = t->rx_buf;
while (likely(count > 0)) {
u8 word = 0;
if (tx)
word = *tx++;
word = txrx_word(spi, ns, word, bits, flags);
if (rx)
*rx++ = word;
count -= 1;
}
return t->len - count;
}
static unsigned bitbang_txrx_16(
struct spi_device *spi,
u32 (*txrx_word)(struct spi_device *spi,
unsigned nsecs,
u32 word, u8 bits,
unsigned flags),
unsigned ns,
struct spi_transfer *t,
unsigned flags
) {
unsigned bits = t->bits_per_word;
unsigned count = t->len;
const u16 *tx = t->tx_buf;
u16 *rx = t->rx_buf;
while (likely(count > 1)) {
u16 word = 0;
if (tx)
word = *tx++;
word = txrx_word(spi, ns, word, bits, flags);
if (rx)
*rx++ = word;
count -= 2;
}
return t->len - count;
}
static unsigned bitbang_txrx_32(
struct spi_device *spi,
u32 (*txrx_word)(struct spi_device *spi,
unsigned nsecs,
u32 word, u8 bits,
unsigned flags),
unsigned ns,
struct spi_transfer *t,
unsigned flags
) {
unsigned bits = t->bits_per_word;
unsigned count = t->len;
const u32 *tx = t->tx_buf;
u32 *rx = t->rx_buf;
while (likely(count > 3)) {
u32 word = 0;
if (tx)
word = *tx++;
word = txrx_word(spi, ns, word, bits, flags);
if (rx)
*rx++ = word;
count -= 4;
}
return t->len - count;
}
int spi_bitbang_setup_transfer(struct spi_device *spi, struct spi_transfer *t)
{
struct spi_bitbang_cs *cs = spi->controller_state;
u8 bits_per_word;
u32 hz;
if (t) {
bits_per_word = t->bits_per_word;
hz = t->speed_hz;
} else {
bits_per_word = 0;
hz = 0;
}
/* spi_transfer level calls that work per-word */
if (!bits_per_word)
bits_per_word = spi->bits_per_word;
if (bits_per_word <= 8)
cs->txrx_bufs = bitbang_txrx_8;
else if (bits_per_word <= 16)
cs->txrx_bufs = bitbang_txrx_16;
else if (bits_per_word <= 32)
cs->txrx_bufs = bitbang_txrx_32;
else
return -EINVAL;
/* nsecs = (clock period)/2 */
if (!hz)
hz = spi->max_speed_hz;
if (hz) {
cs->nsecs = (1000000000/2) / hz;
if (cs->nsecs > (MAX_UDELAY_MS * 1000 * 1000))
return -EINVAL;
}
return 0;
}
EXPORT_SYMBOL_GPL(spi_bitbang_setup_transfer);
/**
* spi_bitbang_setup - default setup for per-word I/O loops
*/
int spi_bitbang_setup(struct spi_device *spi)
{
struct spi_bitbang_cs *cs = spi->controller_state;
struct spi_bitbang *bitbang;
bitbang = spi_master_get_devdata(spi->master);
if (!cs) {
cs = kzalloc(sizeof(*cs), GFP_KERNEL);
if (!cs)
return -ENOMEM;
spi->controller_state = cs;
}
/* per-word shift register access, in hardware or bitbanging */
cs->txrx_word = bitbang->txrx_word[spi->mode & (SPI_CPOL|SPI_CPHA)];
if (!cs->txrx_word)
return -EINVAL;
if (bitbang->setup_transfer) {
int retval = bitbang->setup_transfer(spi, NULL);
if (retval < 0)
return retval;
}
dev_dbg(&spi->dev, "%s, %u nsec/bit\n", __func__, 2 * cs->nsecs);
/* NOTE we _need_ to call chipselect() early, ideally with adapter
* setup, unless the hardware defaults cooperate to avoid confusion
* between normal (active low) and inverted chipselects.
*/
/* deselect chip (low or high) */
mutex_lock(&bitbang->lock);
if (!bitbang->busy) {
bitbang->chipselect(spi, BITBANG_CS_INACTIVE);
ndelay(cs->nsecs);
}
mutex_unlock(&bitbang->lock);
return 0;
}
EXPORT_SYMBOL_GPL(spi_bitbang_setup);
/**
* spi_bitbang_cleanup - default cleanup for per-word I/O loops
*/
void spi_bitbang_cleanup(struct spi_device *spi)
{
kfree(spi->controller_state);
}
EXPORT_SYMBOL_GPL(spi_bitbang_cleanup);
static int spi_bitbang_bufs(struct spi_device *spi, struct spi_transfer *t)
{
struct spi_bitbang_cs *cs = spi->controller_state;
unsigned nsecs = cs->nsecs;
struct spi_bitbang *bitbang;
bitbang = spi_master_get_devdata(spi->master);
if (bitbang->set_line_direction) {
int err;
err = bitbang->set_line_direction(spi, !!(t->tx_buf));
if (err < 0)
return err;
}
if (spi->mode & SPI_3WIRE) {
unsigned flags;
flags = t->tx_buf ? SPI_MASTER_NO_RX : SPI_MASTER_NO_TX;
return cs->txrx_bufs(spi, cs->txrx_word, nsecs, t, flags);
}
return cs->txrx_bufs(spi, cs->txrx_word, nsecs, t, 0);
}
/*----------------------------------------------------------------------*/
/*
* SECOND PART ... simple transfer queue runner.
*
* This costs a task context per controller, running the queue by
* performing each transfer in sequence. Smarter hardware can queue
* several DMA transfers at once, and process several controller queues
* in parallel; this driver doesn't match such hardware very well.
*
* Drivers can provide word-at-a-time i/o primitives, or provide
* transfer-at-a-time ones to leverage dma or fifo hardware.
*/
static int spi_bitbang_prepare_hardware(struct spi_master *spi)
{
struct spi_bitbang *bitbang;
bitbang = spi_master_get_devdata(spi);
mutex_lock(&bitbang->lock);
bitbang->busy = 1;
mutex_unlock(&bitbang->lock);
return 0;
}
static int spi_bitbang_transfer_one(struct spi_master *master,
struct spi_device *spi,
struct spi_transfer *transfer)
{
struct spi_bitbang *bitbang = spi_master_get_devdata(master);
int status = 0;
if (bitbang->setup_transfer) {
status = bitbang->setup_transfer(spi, transfer);
if (status < 0)
goto out;
}
if (transfer->len)
status = bitbang->txrx_bufs(spi, transfer);
if (status == transfer->len)
status = 0;
else if (status >= 0)
status = -EREMOTEIO;
out:
spi_finalize_current_transfer(master);
return status;
}
static int spi_bitbang_unprepare_hardware(struct spi_master *spi)
{
struct spi_bitbang *bitbang;
bitbang = spi_master_get_devdata(spi);
mutex_lock(&bitbang->lock);
bitbang->busy = 0;
mutex_unlock(&bitbang->lock);
return 0;
}
static void spi_bitbang_set_cs(struct spi_device *spi, bool enable)
{
struct spi_bitbang *bitbang = spi_master_get_devdata(spi->master);
/* SPI core provides CS high / low, but bitbang driver
* expects CS active
* spi device driver takes care of handling SPI_CS_HIGH
*/
enable = (!!(spi->mode & SPI_CS_HIGH) == enable);
ndelay(SPI_BITBANG_CS_DELAY);
bitbang->chipselect(spi, enable ? BITBANG_CS_ACTIVE :
BITBANG_CS_INACTIVE);
ndelay(SPI_BITBANG_CS_DELAY);
}
/*----------------------------------------------------------------------*/
/**
* spi_bitbang_start - start up a polled/bitbanging SPI master driver
* @bitbang: driver handle
*
* Caller should have zero-initialized all parts of the structure, and then
* provided callbacks for chip selection and I/O loops. If the master has
* a transfer method, its final step should call spi_bitbang_transfer; or,
* that's the default if the transfer routine is not initialized. It should
* also set up the bus number and number of chipselects.
*
* For i/o loops, provide callbacks either per-word (for bitbanging, or for
* hardware that basically exposes a shift register) or per-spi_transfer
* (which takes better advantage of hardware like fifos or DMA engines).
*
* Drivers using per-word I/O loops should use (or call) spi_bitbang_setup,
* spi_bitbang_cleanup and spi_bitbang_setup_transfer to handle those spi
* master methods. Those methods are the defaults if the bitbang->txrx_bufs
* routine isn't initialized.
*
* This routine registers the spi_master, which will process requests in a
* dedicated task, keeping IRQs unblocked most of the time. To stop
* processing those requests, call spi_bitbang_stop().
*
* On success, this routine will take a reference to master. The caller is
* responsible for calling spi_bitbang_stop() to decrement the reference and
* spi_master_put() as counterpart of spi_alloc_master() to prevent a memory
* leak.
*/
int spi_bitbang_start(struct spi_bitbang *bitbang)
{
struct spi_master *master = bitbang->master;
int ret;
if (!master || !bitbang->chipselect)
return -EINVAL;
mutex_init(&bitbang->lock);
if (!master->mode_bits)
master->mode_bits = SPI_CPOL | SPI_CPHA | bitbang->flags;
if (master->transfer || master->transfer_one_message)
return -EINVAL;
master->prepare_transfer_hardware = spi_bitbang_prepare_hardware;
master->unprepare_transfer_hardware = spi_bitbang_unprepare_hardware;
master->transfer_one = spi_bitbang_transfer_one;
master->set_cs = spi_bitbang_set_cs;
if (!bitbang->txrx_bufs) {
bitbang->use_dma = 0;
bitbang->txrx_bufs = spi_bitbang_bufs;
if (!master->setup) {
if (!bitbang->setup_transfer)
bitbang->setup_transfer =
spi_bitbang_setup_transfer;
master->setup = spi_bitbang_setup;
master->cleanup = spi_bitbang_cleanup;
}
}
/* driver may get busy before register() returns, especially
* if someone registered boardinfo for devices
*/
ret = spi_register_master(spi_master_get(master));
if (ret)
spi_master_put(master);
return 0;
}
EXPORT_SYMBOL_GPL(spi_bitbang_start);
/**
* spi_bitbang_stop - stops the task providing spi communication
*/
void spi_bitbang_stop(struct spi_bitbang *bitbang)
{
spi_unregister_master(bitbang->master);
}
EXPORT_SYMBOL_GPL(spi_bitbang_stop);
MODULE_LICENSE("GPL");
