serial: 8250: of: Load TX FIFO Threshold from DT

Initialize the tx_loadsz parameter from passed in devicetree
tx-threshold parameter.
The tx_loadsz is calculated as the number of bytes to fill FIFO
when tx-threshold is triggered.

Signed-off-by: Thor Thayer <tthayer@opensource.altera.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/8250/8250_of.c b/drivers/tty/serial/8250/8250_of.c
index 38963d7bcf8410520916bdc5bcfbd28de31f958a..7a8b5fc81a192f081add58d5a1a212f9c5a41093 100644 (file)
--- a/drivers/tty/serial/8250/8250_of.c
+++ b/drivers/tty/serial/8250/8250_of.c
@@ -195,6 +195,7 @@ static int of_platform_serial_probe(struct platform_device *ofdev)
        switch (port_type) {
        case PORT_8250 ... PORT_MAX_8250:
        {
+               u32 tx_threshold;
                struct uart_8250_port port8250;
                memset(&port8250, 0, sizeof(port8250));
                port8250.port = port;
@@ -202,6 +203,12 @@ static int of_platform_serial_probe(struct platform_device *ofdev)
                if (port.fifosize)
                        port8250.capabilities = UART_CAP_FIFO;
 
+               /* Check for TX FIFO threshold & set tx_loadsz */
+               if ((of_property_read_u32(ofdev->dev.of_node, "tx-threshold",
+                                         &tx_threshold) == 0) &&
+                   (tx_threshold < port.fifosize))
+                       port8250.tx_loadsz = port.fifosize - tx_threshold;
+
                if (of_property_read_bool(ofdev->dev.of_node,
                                          "auto-flow-control"))
                        port8250.capabilities |= UART_CAP_AFE;