Commit 9119fba0 authored by Andy Shevchenko's avatar Andy Shevchenko Committed by Greg Kroah-Hartman

serial: 8250_dma: don't bother DMA with small transfers

If we would like to send amount of data less than FIFO size we better would do
this via PIO mode. Otherwise the overhead could be significant.
Signed-off-by: default avatarAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent a39d1da1
...@@ -80,6 +80,10 @@ int serial8250_tx_dma(struct uart_8250_port *p) ...@@ -80,6 +80,10 @@ int serial8250_tx_dma(struct uart_8250_port *p)
return 0; return 0;
dma->tx_size = CIRC_CNT_TO_END(xmit->head, xmit->tail, UART_XMIT_SIZE); 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, desc = dmaengine_prep_slave_single(dma->txchan,
dma->tx_addr + xmit->tail, dma->tx_addr + xmit->tail,
......
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