mpc52xx_psc_spi: fix block transfer
Luotao Fu [Mon, 28 Jul 2008 22:46:32 +0000 (15:46 -0700)]
The block transfer routine in the mpc52xx psc spi driver misinterpret
the datasheet.  According to the processor datasheet the chipselect is
held as long as the EOF is not written.

Theoretically blocks of any sizes can be transferred in this way.  The
old routine however writes an EOF after every word, which has the size
of size_of_word.  This makes the transfer slow.

Also fixed some duplicate code.

Signed-off-by: Luotao Fu <l.fu@pengutronix.de>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: <stable@kernel.org> [2.6.25.x, 2.6.26.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/spi/mpc52xx_psc_spi.c

index 604e5f0..25eda71 100644 (file)
@@ -148,7 +148,6 @@ static int mpc52xx_psc_spi_transfer_rxtx(struct spi_device *spi,
        unsigned rfalarm;
        unsigned send_at_once = MPC52xx_PSC_BUFSIZE;
        unsigned recv_at_once;
-       unsigned bpw = mps->bits_per_word / 8;
 
        if (!t->tx_buf && !t->rx_buf && t->len)
                return -EINVAL;
@@ -164,22 +163,15 @@ static int mpc52xx_psc_spi_transfer_rxtx(struct spi_device *spi,
                }
 
                dev_dbg(&spi->dev, "send %d bytes...\n", send_at_once);
-               if (tx_buf) {
-                       for (; send_at_once; sb++, send_at_once--) {
-                               /* set EOF flag */
-                               if (mps->bits_per_word
-                                               && (sb + 1) % bpw == 0)
-                                       out_8(&psc->ircr2, 0x01);
+               for (; send_at_once; sb++, send_at_once--) {
+                       /* set EOF flag before the last word is sent */
+                       if (send_at_once == 1)
+                               out_8(&psc->ircr2, 0x01);
+
+                       if (tx_buf)
                                out_8(&psc->mpc52xx_psc_buffer_8, tx_buf[sb]);
-                       }
-               } else {
-                       for (; send_at_once; sb++, send_at_once--) {
-                               /* set EOF flag */
-                               if (mps->bits_per_word
-                                               && ((sb + 1) % bpw) == 0)
-                                       out_8(&psc->ircr2, 0x01);
+                       else
                                out_8(&psc->mpc52xx_psc_buffer_8, 0);
-                       }
                }