[PATCH 4.2 071/110] Revert "serial: 8250_dma: dont bother DMA with small transfers"

[Greg Kroah-Hartman]

4.2-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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