dm355_spi_bitbang.c

TI的达芬奇系列dm355使用的spi模块驱动

                unsigned cs_change;
                int status;
                int (*setup_transfer) (struct spi_device *,
                                       struct spi_transfer *);

                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;
                setup_transfer = NULL;

                list_for_each_entry(t, &m->transfers, transfer_list) {
                        if (bitbang->shutdown) {
                                status = -ESHUTDOWN;
                                break;
                        }

                        /* override or restore speed and wordsize */
                        if (t->speed_hz || t->bits_per_word) {
                                setup_transfer = bitbang->setup_transfer;
                                if (!setup_transfer) {
                                        status = -ENOPROTOOPT;
                                        break;
                                }
                        }
                        if (setup_transfer) {
                                DEBUG_BB("setup_transfer is being called\n");
                                status = setup_transfer(spi, t);
                                if (status < 0)
                                        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;
                                DEBUG_BB("bitbang->txrx_bufs called\n");
                                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);

                /* restore speed and wordsize */
                if (setup_transfer)
                        setup_transfer(spi, NULL);

                /* 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);
}




/**
 * dm355_spi_bitbang_transfer - default submit to transfer queue
 */
int dm355_spi_bitbang_transfer(struct spi_device *spi,
                               struct spi_message *m)
{
        struct spi_bitbang *bitbang;
        unsigned long flags;
        int status = 0;

        ENTER 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);
        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);

        EXIT return status;
}

EXPORT_SYMBOL_GPL(dm355_spi_bitbang_transfer);

/*----------------------------------------------------------------------*/

/**
 * dm355_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 dm355_spi_bitbang_start(struct spi_bitbang *bitbang)
{
        int status;

        if (!bitbang->master || !bitbang->chipselect)
                return -EINVAL;

        INIT_WORK(&bitbang->work, dm355_bitbang_work, bitbang);
        spin_lock_init(&bitbang->lock);
        INIT_LIST_HEAD(&bitbang->queue);

        if (!bitbang->master->transfer)
                bitbang->master->transfer = dm355_spi_bitbang_transfer;
        if (!bitbang->txrx_bufs) {
                bitbang->use_dma = 0;
                bitbang->txrx_bufs = dm355_spi_bitbang_bufs;
                if (!bitbang->master->setup) {
                        if (!bitbang->setup_transfer)
                                bitbang->setup_transfer =
                                    dm355_spi_bitbang_setup_transfer;
                        bitbang->master->setup = dm355_spi_bitbang_setup;
                        bitbang->master->cleanup =
                            dm355_spi_bitbang_cleanup;
                }
        } else if (!bitbang->master->setup)
                return -EINVAL;

        /* this task is the only thing to touch the SPI bits */
        bitbang->busy = 0;

        DEBUG_BB("bus_id = %s\n", bitbang->master->cdev.dev->bus_id);

        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(dm355_spi_bitbang_start);

/**
 * spi_bitbang_stop - stops the task providing spi communication
 */
int dm355_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(dm355_spi_bitbang_stop);

MODULE_LICENSE("GPL");