As of commit eedacbf0, drivers/serial/of_serial.c forces the serial core to recognize the xps-uart16550-2.00.b as an NS16550 (which had no FIFO). Prior to this commit, the kernel's auto-configuration logic would correctly recognize the UART as NS16550A (with 16-byte FIFO).
The following patch corrects the issue in what I believe to be the
correct way:
---
Xilinx 16550 UART is actually 16550A-compatible
diff --git a/drivers/serial/of_serial.c b/drivers/serial/of_serial.c
index 02406ba..78267af 100644
--- a/drivers/serial/of_serial.c
+++ b/drivers/serial/of_serial.c
@@ -161,7 +161,7 @@ static int of_platform_serial_remove(struct
of_device *ofdev)
static struct of_device_id __devinitdata of_platform_serial_table[] = {
{ .type = "serial", .compatible = "ns8250", .data = (void
*)PORT_8250, },
{ .type = "serial", .compatible = "ns16450", .data = (void
*)PORT_16450, },
- { .type = "serial", .compatible = "ns16550", .data = (void
*)PORT_16550, },
+ { .type = "serial", .compatible = "ns16550", .data = (void
*)PORT_16550A, },
{ .type = "serial", .compatible = "ns16750", .data = (void
*)PORT_16750, },
{ .type = "serial", .compatible = "ns16850", .data = (void
*)PORT_16850, },
#ifdef CONFIG_SERIAL_OF_PLATFORM_NWPSERIAL
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03-of_serial-16550A.patch
Description: 03-of_serial-16550A.patch
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