[PATCH 4.1 51/86] Revert "serial: 8250_dma: dont bother DMA with small transfers"

From: Greg Kroah-Hartman
Date: Fri Nov 06 2015 - 15:15:55 EST

4.1-stable review patch. If anyone has any objections, please let me know.


From: Frederic Danis <frederic.danis@xxxxxxxxxxxxxxx>

commit f967fc8f165fadb72166f2bd4785094b3ca21307 upstream.

This reverts commit 9119fba0cfeda6d415c9f068df66838a104b87cb.

This commit prevents from sending "big" file using Bluetooth.
When sending a lot of data quickly through the Bluetooth interface, and
after a variable amount of data sent, transfer fails with error:
kernel: [ 415.247453] Bluetooth: hci0 hardware error 0x00

Found on T100TA.

After reverting this commit, send works fine for any file size.

Signed-off-by: Frederic Danis <frederic.danis@xxxxxxxxxxxxxxx>
Fixes: 9119fba0cfed (serial: 8250_dma: don't bother DMA with small transfers)
Reviewed-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
Acked-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

drivers/tty/serial/8250/8250_dma.c | 4 ----
1 file changed, 4 deletions(-)

--- a/drivers/tty/serial/8250/8250_dma.c
+++ b/drivers/tty/serial/8250/8250_dma.c
@@ -80,10 +80,6 @@ int serial8250_tx_dma(struct uart_8250_p
return 0;

dma->tx_size = CIRC_CNT_TO_END(xmit->head, xmit->tail, UART_XMIT_SIZE);
- if (dma->tx_size < p->port.fifosize) {
- ret = -EINVAL;
- goto err;
- }

desc = dmaengine_prep_slave_single(dma->txchan,
dma->tx_addr + xmit->tail,

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