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path: root/drivers/spi/spi-bitbang.c
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Diffstat (limited to 'drivers/spi/spi-bitbang.c')
-rw-r--r--drivers/spi/spi-bitbang.c505
1 files changed, 505 insertions, 0 deletions
diff --git a/drivers/spi/spi-bitbang.c b/drivers/spi/spi-bitbang.c
new file mode 100644
index 00000000000..02d57fbba29
--- /dev/null
+++ b/drivers/spi/spi-bitbang.c
@@ -0,0 +1,505 @@
+/*
+ * 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/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 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 ? : 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 = t->bits_per_word ? : 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 = t->bits_per_word ? : 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;
+}
+
+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 void bitbang_work(struct work_struct *work)
+{
+ struct spi_bitbang *bitbang =
+ container_of(work, struct spi_bitbang, work);
+ 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;
+ int do_setup = -1;
+
+ 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) {
+
+ /* 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)
+ 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;
+ int status = 0;
+
+ m->actual_length = 0;
+ m->status = -EINPROGRESS;
+
+ bitbang = spi_master_get_devdata(spi->master);
+
+ spin_lock_irqsave(&bitbang->lock, flags);
+ if (!spi->max_speed_hz)
+ status = -ENETDOWN;
+ else {
+ list_add_tail(&m->queue, &bitbang->queue);
+ queue_work(bitbang->workqueue, &bitbang->work);
+ }
+ spin_unlock_irqrestore(&bitbang->lock, flags);
+
+ return status;
+}
+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,
+ * 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().
+ */
+int spi_bitbang_start(struct spi_bitbang *bitbang)
+{
+ int status;
+
+ if (!bitbang->master || !bitbang->chipselect)
+ return -EINVAL;
+
+ INIT_WORK(&bitbang->work, bitbang_work);
+ spin_lock_init(&bitbang->lock);
+ INIT_LIST_HEAD(&bitbang->queue);
+
+ if (!bitbang->master->mode_bits)
+ bitbang->master->mode_bits = SPI_CPOL | SPI_CPHA | bitbang->flags;
+
+ 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) {
+ if (!bitbang->setup_transfer)
+ bitbang->setup_transfer =
+ spi_bitbang_setup_transfer;
+ bitbang->master->setup = spi_bitbang_setup;
+ bitbang->master->cleanup = spi_bitbang_cleanup;
+ }
+ } else if (!bitbang->master->setup)
+ return -EINVAL;
+ if (bitbang->master->transfer == spi_bitbang_transfer &&
+ !bitbang->setup_transfer)
+ return -EINVAL;
+
+ /* this task is the only thing to touch the SPI bits */
+ bitbang->busy = 0;
+ bitbang->workqueue = create_singlethread_workqueue(
+ dev_name(bitbang->master->dev.parent));
+ 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)
+{
+ spi_unregister_master(bitbang->master);
+
+ WARN_ON(!list_empty(&bitbang->queue));
+
+ destroy_workqueue(bitbang->workqueue);
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(spi_bitbang_stop);
+
+MODULE_LICENSE("GPL");
+
generated by cgit v1.2.3-18-g5258 (git 2.32.0) at 2024-12-11 20:31:46 +0000