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 (file)
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -178,6 +178,7 @@ dw8250_acpi_walk_resource(struct acpi_resource *res, void *data)
                        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 @@ dw8250_acpi_walk_resource(struct acpi_resource *res, void *data)
                        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 @@ static int dw8250_probe(struct platform_device *pdev)
        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 @@ static int dw8250_probe(struct platform_device *pdev)
                return -ENODEV;
        }
 
-       dw8250_setup_port(&uart);
-
        data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
        if (!data)
                return -ENOMEM;