serial: 8250_dw: Set maxburst size
The default burst is often 1 byte which is not very optimal.
The ideal burst size when using 16550A type port would be
1/2 of fifosize, but this does not work with all Designware
implementations. Setting it to 1/4 fifosize.
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index bfdaf8b..117bb8b 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -178,6 +178,7 @@
slave->direction = DMA_MEM_TO_DEV;
slave->dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
slave->slave_id = fixed_dma->request_lines;
+ slave->dst_maxburst = port->tx_loadsz / 4;
dma->tx_chan_id = fixed_dma->channels;
dma->tx_param = &dma->tx_chan_id;
@@ -189,6 +190,7 @@
slave->direction = DMA_DEV_TO_MEM;
slave->src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
slave->slave_id = fixed_dma->request_lines;
+ slave->src_maxburst = p->fifosize / 4;
dma->rx_chan_id = fixed_dma->channels;
dma->rx_param = &dma->rx_chan_id;
@@ -296,6 +298,8 @@
uart.port.serial_in = dw8250_serial_in;
uart.port.serial_out = dw8250_serial_out;
+ dw8250_setup_port(&uart);
+
if (pdev->dev.of_node) {
err = dw8250_probe_of(&uart.port);
if (err)
@@ -308,8 +312,6 @@
return -ENODEV;
}
- dw8250_setup_port(&uart);
-
data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
if (!data)
return -ENOMEM;