linux/drivers/spi/spi-bitbang.c
Alban Bedel a666f2619a
spi: bitbang: Don't call chipselect() in spi_bitbang_setup()
spi_setup() already call spi_set_cs() right after calling the
controller setup method, so there is no need for the bitbang driver to
do that. Because of this the chipselect() callback was confusingly
still called when CS is GPIO based.

Signed-off-by: Alban Bedel <albeu@free.fr>
Signed-off-by: Mark Brown <broonie@kernel.org>
2019-01-17 12:34:14 +00:00

421 lines
11 KiB
C

/*
* 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);
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");