spi: bitbang bugfix in message setup
Bugfix to spi_bitbang infrastructure: make sure to always set transfer
parameters on the first pass through the message's per-transfer loop.
This can matter with drivers that replace the per-word or per-buffer
transfer primitives, on busses with multiple SPI devices.
Previously, this could have started messages using the settings left after
previous messages. The problem was observed when a high speed chip
(m25p80 type flash) was running very slowly because a low speed device
(avr8 microcontroller) had previously used the bus. Similar faults could
have driven the low speed device too fast, or used an unexpected word
size.
Acked-by: Steven A. Falco <sfalco@harris.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/spi/spi_bitbang.c b/drivers/spi/spi_bitbang.c
index 2a5abc0..f1db395 100644
--- a/drivers/spi/spi_bitbang.c
+++ b/drivers/spi/spi_bitbang.c
@@ -258,6 +258,11 @@
struct spi_bitbang *bitbang =
container_of(work, struct spi_bitbang, work);
unsigned long flags;
+ int do_setup = -1;
+ int (*setup_transfer)(struct spi_device *,
+ struct spi_transfer *);
+
+ setup_transfer = bitbang->setup_transfer;
spin_lock_irqsave(&bitbang->lock, flags);
bitbang->busy = 1;
@@ -269,8 +274,6 @@
unsigned tmp;
unsigned cs_change;
int status;
- int (*setup_transfer)(struct spi_device *,
- struct spi_transfer *);
m = container_of(bitbang->queue.next, struct spi_message,
queue);
@@ -287,19 +290,19 @@
tmp = 0;
cs_change = 1;
status = 0;
- setup_transfer = NULL;
list_for_each_entry (t, &m->transfers, transfer_list) {
- /* override or restore speed and wordsize */
- if (t->speed_hz || t->bits_per_word) {
- setup_transfer = bitbang->setup_transfer;
+ /* 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) {
if (!setup_transfer) {
status = -ENOPROTOOPT;
break;
}
- }
- if (setup_transfer) {
status = setup_transfer(spi, t);
if (status < 0)
break;
@@ -363,9 +366,10 @@
m->status = status;
m->complete(m->context);
- /* restore speed and wordsize */
- if (setup_transfer)
+ /* restore speed and wordsize if it was overridden */
+ if (do_setup == 1)
setup_transfer(spi, NULL);
+ do_setup = 0;
/* normally deactivate chipselect ... unless no error and
* cs_change has hinted that the next message will probably