1 files changed, 49 insertions, 37 deletions

diff --git a/drivers/spi/spi_bitbang.c b/drivers/spi/spi_bitbang.c
index 44aff198eb96..f037e5593269 100644
--- a/drivers/spi/spi_bitbang.c
+++ b/drivers/spi/spi_bitbang.c
@@ -146,6 +146,9 @@ 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)
@@ -172,13 +175,8 @@ int spi_bitbang_setup(struct spi_device *spi)
         if (!cs->txrx_word)
                 return -EINVAL;
 
-        if (!spi->max_speed_hz)
-                spi->max_speed_hz = 500 * 1000;
-
-        /* nsecs = max(50, (clock period)/2), be optimistic */
+        /* nsecs = (clock period)/2 */
         cs->nsecs = (1000000000/2) / (spi->max_speed_hz);
-        if (cs->nsecs < 50)
-                cs->nsecs = 50;
         if (cs->nsecs > MAX_UDELAY_MS * 1000)
                 return -EINVAL;
 
@@ -194,7 +192,7 @@ int spi_bitbang_setup(struct spi_device *spi)
         /* deselect chip (low or high) */
         spin_lock(&bitbang->lock);
         if (!bitbang->busy) {
-                bitbang->chipselect(spi, 0);
+                bitbang->chipselect(spi, BITBANG_CS_INACTIVE);
                 ndelay(cs->nsecs);
         }
         spin_unlock(&bitbang->lock);
@@ -244,9 +242,9 @@ static void bitbang_work(void *_bitbang)
                 struct spi_message      *m;
                 struct spi_device       *spi;
                 unsigned                nsecs;
-                struct spi_transfer     *t;
+                struct spi_transfer     *t = NULL;
                 unsigned                tmp;
-                unsigned                chipselect;
+                unsigned                cs_change;
                 int                     status;
 
                 m = container_of(bitbang->queue.next, struct spi_message,
@@ -254,37 +252,49 @@ static void bitbang_work(void *_bitbang)
                 list_del_init(&m->queue);
                 spin_unlock_irqrestore(&bitbang->lock, flags);
 
-// FIXME this is made-up
-nsecs = 100;
+                /* 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;
-                t = m->transfers;
                 tmp = 0;
-                chipselect = 0;
+                cs_change = 1;
                 status = 0;
 
-                for (;;t++) {
+                list_for_each_entry (t, &m->transfers, transfer_list) {
                         if (bitbang->shutdown) {
                                 status = -ESHUTDOWN;
                                 break;
                         }
 
-                        /* set up default clock polarity, and activate chip */
-                        if (!chipselect) {
-                                bitbang->chipselect(spi, 1);
+                        /* 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 */
+                        /* transfer data.  the lower level code handles any
+                         * new dma mappings it needs. our caller always gave
+                         * us dma-safe buffers.
+                         */
                         if (t->len) {
-                                /* FIXME if bitbang->use_dma, dma_map_single()
-                                 * before the transfer, and dma_unmap_single()
-                                 * afterwards, for either or both buffers...
+                                /* 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) {
@@ -299,29 +309,31 @@ nsecs = 100;
                         if (t->delay_usecs)
                                 udelay(t->delay_usecs);
 
-                        tmp++;
-                        if (tmp >= m->n_transfer)
-                                break;
-
-                        chipselect = !t->cs_change;
-                        if (chipselect);
+                        if (!cs_change)
                                 continue;
+                        if (t->transfer_list.next == &m->transfers)
+                                break;
 
-                        bitbang->chipselect(spi, 0);
-
-                        /* REVISIT do we want the udelay here instead? */
-                        msleep(1);
+                        /* 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);
                 }
 
-                tmp = m->n_transfer - 1;
-                tmp = m->transfers[tmp].cs_change;
-
                 m->status = status;
                 m->complete(m->context);
 
-                ndelay(2 * nsecs);
-                bitbang->chipselect(spi, status == 0 && tmp);
-                ndelay(nsecs);
+                /* 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);
         }