Skip to content

Commit

Permalink
spi: mpc52xx_psc_spi chipselect bugfix
Browse files Browse the repository at this point in the history
According to the manual the "tdfOnExit" flag must be set on the last byte
we want to send.  The PSC controller holds SS low until the flag is set.

However, the flag was set always on the last byte of the FIFO,
independently if it is the last byte of the transfer.  This generates
spurious toggling of the SS signals that breaks the protocol of some
peripherals.  Fix.

Signed-off-by: Stefano Babic <sbabic@denx.de>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
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>
  • Loading branch information
Stefano Babic authored and Linus Torvalds committed Dec 2, 2008
1 parent aaacf4b commit b7d271d
Showing 1 changed file with 4 additions and 1 deletion.
5 changes: 4 additions & 1 deletion drivers/spi/mpc52xx_psc_spi.c
Original file line number Diff line number Diff line change
Expand Up @@ -142,6 +142,7 @@ static int mpc52xx_psc_spi_transfer_rxtx(struct spi_device *spi,
unsigned rfalarm;
unsigned send_at_once = MPC52xx_PSC_BUFSIZE;
unsigned recv_at_once;
int last_block = 0;

if (!t->tx_buf && !t->rx_buf && t->len)
return -EINVAL;
Expand All @@ -151,15 +152,17 @@ static int mpc52xx_psc_spi_transfer_rxtx(struct spi_device *spi,
while (rb < t->len) {
if (t->len - rb > MPC52xx_PSC_BUFSIZE) {
rfalarm = MPC52xx_PSC_RFALARM;
last_block = 0;
} else {
send_at_once = t->len - sb;
rfalarm = MPC52xx_PSC_BUFSIZE - (t->len - rb);
last_block = 1;
}

dev_dbg(&spi->dev, "send %d bytes...\n", send_at_once);
for (; send_at_once; sb++, send_at_once--) {
/* set EOF flag before the last word is sent */
if (send_at_once == 1)
if (send_at_once == 1 && last_block)
out_8(&psc->ircr2, 0x01);

if (tx_buf)
Expand Down

0 comments on commit b7d271d

Please sign in to comment.