diff options
Diffstat (limited to 'drivers/spi/spi_bitbang.c')
| -rw-r--r-- | drivers/spi/spi_bitbang.c | 472 |
1 files changed, 472 insertions, 0 deletions
diff --git a/drivers/spi/spi_bitbang.c b/drivers/spi/spi_bitbang.c new file mode 100644 index 00000000000..f037e559326 --- /dev/null +++ b/drivers/spi/spi_bitbang.c @@ -0,0 +1,472 @@ +/* + * spi_bitbang.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. + * + * 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA + */ + +#include <linux/config.h> +#include <linux/init.h> +#include <linux/spinlock.h> +#include <linux/workqueue.h> +#include <linux/interrupt.h> +#include <linux/delay.h> +#include <linux/errno.h> +#include <linux/platform_device.h> + +#include <linux/spi/spi.h> +#include <linux/spi/spi_bitbang.h> + + +/*----------------------------------------------------------------------*/ + +/* + * 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 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 (*txrx_bufs)(struct spi_device *, + u32 (*txrx_word)( + struct spi_device *spi, + unsigned nsecs, + u32 word, u8 bits), + unsigned, struct spi_transfer *); +}; + +static unsigned bitbang_txrx_8( + struct spi_device *spi, + u32 (*txrx_word)(struct spi_device *spi, + unsigned nsecs, + u32 word, u8 bits), + unsigned ns, + struct spi_transfer *t +) { + unsigned bits = spi->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); + 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 ns, + struct spi_transfer *t +) { + unsigned bits = spi->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); + 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 ns, + struct spi_transfer *t +) { + unsigned bits = spi->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); + if (rx) + *rx++ = word; + count -= 4; + } + return t->len - count; +} + +/** + * 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; + + if (!spi->max_speed_hz) + return -EINVAL; + + if (!cs) { + cs = kzalloc(sizeof *cs, SLAB_KERNEL); + if (!cs) + return -ENOMEM; + spi->controller_state = cs; + } + bitbang = spi_master_get_devdata(spi->master); + + if (!spi->bits_per_word) + spi->bits_per_word = 8; + + /* spi_transfer level calls that work per-word */ + if (spi->bits_per_word <= 8) + cs->txrx_bufs = bitbang_txrx_8; + else if (spi->bits_per_word <= 16) + cs->txrx_bufs = bitbang_txrx_16; + else if (spi->bits_per_word <= 32) + cs->txrx_bufs = bitbang_txrx_32; + else + return -EINVAL; + + /* 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; + + /* nsecs = (clock period)/2 */ + cs->nsecs = (1000000000/2) / (spi->max_speed_hz); + if (cs->nsecs > MAX_UDELAY_MS * 1000) + return -EINVAL; + + dev_dbg(&spi->dev, "%s, mode %d, %u bits/w, %u nsec\n", + __FUNCTION__, spi->mode & (SPI_CPOL | SPI_CPHA), + spi->bits_per_word, 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) */ + spin_lock(&bitbang->lock); + if (!bitbang->busy) { + bitbang->chipselect(spi, BITBANG_CS_INACTIVE); + ndelay(cs->nsecs); + } + spin_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(const 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; + + return cs->txrx_bufs(spi, cs->txrx_word, nsecs, t); +} + +/*----------------------------------------------------------------------*/ + +/* + * 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 void bitbang_work(void *_bitbang) +{ + struct spi_bitbang *bitbang = _bitbang; + unsigned long flags; + + spin_lock_irqsave(&bitbang->lock, flags); + bitbang->busy = 1; + while (!list_empty(&bitbang->queue)) { + struct spi_message *m; + struct spi_device *spi; + unsigned nsecs; + struct spi_transfer *t = NULL; + unsigned tmp; + unsigned cs_change; + int status; + + m = container_of(bitbang->queue.next, struct spi_message, + queue); + list_del_init(&m->queue); + spin_unlock_irqrestore(&bitbang->lock, flags); + + /* FIXME this is made-up ... the correct value is known to + * word-at-a-time bitbang code, and presumably chipselect() + * should enforce these requirements too? + */ + nsecs = 100; + + spi = m->spi; + tmp = 0; + cs_change = 1; + status = 0; + + list_for_each_entry (t, &m->transfers, transfer_list) { + if (bitbang->shutdown) { + status = -ESHUTDOWN; + break; + } + + /* set up default clock polarity, and activate chip; + * this implicitly updates clock and spi modes as + * previously recorded for this device via setup(). + * (and also deselects any other chip that might be + * selected ...) + */ + if (cs_change) { + bitbang->chipselect(spi, BITBANG_CS_ACTIVE); + ndelay(nsecs); + } + cs_change = t->cs_change; + if (!t->tx_buf && !t->rx_buf && t->len) { + status = -EINVAL; + break; + } + + /* transfer data. the lower level code handles any + * new dma mappings it needs. our caller always gave + * us dma-safe buffers. + */ + if (t->len) { + /* REVISIT dma API still needs a designated + * DMA_ADDR_INVALID; ~0 might be better. + */ + if (!m->is_dma_mapped) + t->rx_dma = t->tx_dma = 0; + status = bitbang->txrx_bufs(spi, t); + } + if (status != t->len) { + if (status > 0) + status = -EMSGSIZE; + break; + } + m->actual_length += status; + status = 0; + + /* protocol tweaks before next transfer */ + if (t->delay_usecs) + udelay(t->delay_usecs); + + if (!cs_change) + continue; + if (t->transfer_list.next == &m->transfers) + break; + + /* sometimes a short mid-message deselect of the chip + * may be needed to terminate a mode or command + */ + ndelay(nsecs); + bitbang->chipselect(spi, BITBANG_CS_INACTIVE); + ndelay(nsecs); + } + + m->status = status; + m->complete(m->context); + + /* normally deactivate chipselect ... unless no error and + * cs_change has hinted that the next message will probably + * be for this chip too. + */ + if (!(status == 0 && cs_change)) { + ndelay(nsecs); + bitbang->chipselect(spi, BITBANG_CS_INACTIVE); + ndelay(nsecs); + } + + spin_lock_irqsave(&bitbang->lock, flags); + } + bitbang->busy = 0; + spin_unlock_irqrestore(&bitbang->lock, flags); +} + +/** + * spi_bitbang_transfer - default submit to transfer queue + */ +int spi_bitbang_transfer(struct spi_device *spi, struct spi_message *m) +{ + struct spi_bitbang *bitbang; + unsigned long flags; + + m->actual_length = 0; + m->status = -EINPROGRESS; + + bitbang = spi_master_get_devdata(spi->master); + if (bitbang->shutdown) + return -ESHUTDOWN; + + spin_lock_irqsave(&bitbang->lock, flags); + list_add_tail(&m->queue, &bitbang->queue); + queue_work(bitbang->workqueue, &bitbang->work); + spin_unlock_irqrestore(&bitbang->lock, flags); + + return 0; +} +EXPORT_SYMBOL_GPL(spi_bitbang_transfer); + +/*----------------------------------------------------------------------*/ + +/** + * 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 and + * spi_bitbang_cleanup 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(). + */ +int spi_bitbang_start(struct spi_bitbang *bitbang) +{ + int status; + + if (!bitbang->master || !bitbang->chipselect) + return -EINVAL; + + INIT_WORK(&bitbang->work, bitbang_work, bitbang); + spin_lock_init(&bitbang->lock); + INIT_LIST_HEAD(&bitbang->queue); + + if (!bitbang->master->transfer) + bitbang->master->transfer = spi_bitbang_transfer; + if (!bitbang->txrx_bufs) { + bitbang->use_dma = 0; + bitbang->txrx_bufs = spi_bitbang_bufs; + if (!bitbang->master->setup) { + bitbang->master->setup = spi_bitbang_setup; + bitbang->master->cleanup = spi_bitbang_cleanup; + } + } else if (!bitbang->master->setup) + return -EINVAL; + + /* this task is the only thing to touch the SPI bits */ + bitbang->busy = 0; + bitbang->workqueue = create_singlethread_workqueue( + bitbang->master->cdev.dev->bus_id); + if (bitbang->workqueue == NULL) { + status = -EBUSY; + goto err1; + } + + /* driver may get busy before register() returns, especially + * if someone registered boardinfo for devices + */ + status = spi_register_master(bitbang->master); + if (status < 0) + goto err2; + + return status; + +err2: + destroy_workqueue(bitbang->workqueue); +err1: + return status; +} +EXPORT_SYMBOL_GPL(spi_bitbang_start); + +/** + * spi_bitbang_stop - stops the task providing spi communication + */ +int spi_bitbang_stop(struct spi_bitbang *bitbang) +{ + unsigned limit = 500; + + spin_lock_irq(&bitbang->lock); + bitbang->shutdown = 0; + while (!list_empty(&bitbang->queue) && limit--) { + spin_unlock_irq(&bitbang->lock); + + dev_dbg(bitbang->master->cdev.dev, "wait for queue\n"); + msleep(10); + + spin_lock_irq(&bitbang->lock); + } + spin_unlock_irq(&bitbang->lock); + if (!list_empty(&bitbang->queue)) { + dev_err(bitbang->master->cdev.dev, "queue didn't empty\n"); + return -EBUSY; + } + + destroy_workqueue(bitbang->workqueue); + + spi_unregister_master(bitbang->master); + + return 0; +} +EXPORT_SYMBOL_GPL(spi_bitbang_stop); + +MODULE_LICENSE("GPL"); + |