[PATCH] spi: use linked lists rather than an array
This makes the SPI core and its users access transfers in the SPI message
structure as linked list not as an array, as discussed on LKML.
From: David Brownell <dbrownell@users.sourceforge.net>
Updates including doc, bugfixes to the list code, add
spi_message_add_tail(). Plus, initialize things _before_ grabbing the
locks in some cases (in case it grows more expensive). This also merges
some bitbang updates of mine that didn't yet make it into the mm tree.
Signed-off-by: Vitaly Wool <vwool@ru.mvista.com>
Signed-off-by: Dmitry Pervushin <dpervushin@gmail.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/spi/spi_bitbang.c b/drivers/spi/spi_bitbang.c
index 44aff19..f037e55 100644
--- a/drivers/spi/spi_bitbang.c
+++ b/drivers/spi/spi_bitbang.c
@@ -146,6 +146,9 @@
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 @@
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 @@
/* 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 @@
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 @@
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 @@
if (t->delay_usecs)
udelay(t->delay_usecs);
- tmp++;
- if (tmp >= m->n_transfer)
+ if (!cs_change)
+ continue;
+ if (t->transfer_list.next == &m->transfers)
break;
- chipselect = !t->cs_change;
- if (chipselect);
- continue;
-
- 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);
}