| /* |
| * 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/init.h> |
| #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> |
| |
| |
| /*----------------------------------------------------------------------*/ |
| |
| /* |
| * 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 (*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 = 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); |
| 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 = 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); |
| 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 = 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); |
| 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; |
| int retval; |
| unsigned long flags; |
| |
| 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; |
| |
| 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) */ |
| spin_lock_irqsave(&bitbang->lock, flags); |
| if (!bitbang->busy) { |
| bitbang->chipselect(spi, BITBANG_CS_INACTIVE); |
| ndelay(cs->nsecs); |
| } |
| spin_unlock_irqrestore(&bitbang->lock, flags); |
| |
| 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; |
| |
| 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 int spi_bitbang_prepare_hardware(struct spi_master *spi) |
| { |
| struct spi_bitbang *bitbang; |
| unsigned long flags; |
| |
| bitbang = spi_master_get_devdata(spi); |
| |
| spin_lock_irqsave(&bitbang->lock, flags); |
| bitbang->busy = 1; |
| spin_unlock_irqrestore(&bitbang->lock, flags); |
| |
| return 0; |
| } |
| |
| static int spi_bitbang_transfer_one(struct spi_master *master, |
| struct spi_message *m) |
| { |
| struct spi_bitbang *bitbang; |
| unsigned nsecs; |
| struct spi_transfer *t = NULL; |
| unsigned cs_change; |
| int status; |
| int do_setup = -1; |
| struct spi_device *spi = m->spi; |
| |
| bitbang = spi_master_get_devdata(master); |
| |
| /* 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; |
| |
| cs_change = 1; |
| status = 0; |
| |
| list_for_each_entry(t, &m->transfers, transfer_list) { |
| |
| /* override speed or wordsize? */ |
| if (t->speed_hz || t->bits_per_word) |
| do_setup = 1; |
| |
| /* init (-1) or override (1) transfer params */ |
| if (do_setup != 0) { |
| status = bitbang->setup_transfer(spi, t); |
| if (status < 0) |
| break; |
| if (do_setup == -1) |
| do_setup = 0; |
| } |
| |
| /* 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 > 0) |
| m->actual_length += status; |
| if (status != t->len) { |
| /* always report some kind of error */ |
| if (status >= 0) |
| status = -EREMOTEIO; |
| break; |
| } |
| status = 0; |
| |
| /* protocol tweaks before next transfer */ |
| if (t->delay_usecs) |
| udelay(t->delay_usecs); |
| |
| if (cs_change && |
| !list_is_last(&t->transfer_list, &m->transfers)) { |
| /* 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; |
| |
| /* 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); |
| } |
| |
| spi_finalize_current_message(master); |
| |
| return status; |
| } |
| |
| static int spi_bitbang_unprepare_hardware(struct spi_master *spi) |
| { |
| struct spi_bitbang *bitbang; |
| unsigned long flags; |
| |
| bitbang = spi_master_get_devdata(spi); |
| |
| spin_lock_irqsave(&bitbang->lock, flags); |
| bitbang->busy = 0; |
| spin_unlock_irqrestore(&bitbang->lock, flags); |
| |
| return 0; |
| } |
| |
| /*----------------------------------------------------------------------*/ |
| |
| /** |
| * 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; |
| |
| spin_lock_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_message = spi_bitbang_transfer_one; |
| |
| 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"); |
| |