Setting the fifo to only 1 byte generates one interrupt every 1ms at 9600 bauds.
This is too much. This patch reduces the threshold to speeds below 2400 bauds
like in the 8250 UART driver.
Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
--- linux-3.5-vanilla/drivers/tty/serial/cpm_uart/cpm_uart_core.c 2012-07-21 22:58:29.000000000 +0200
+++ linux-3.5/drivers/tty/serial/cpm_uart/cpm_uart_core.c 2012-08-09 17:38:37.000000000 +0200
@@ -71,7 +71,7 @@
/**************************************************************/
-#define HW_BUF_SPD_THRESHOLD 9600
+#define HW_BUF_SPD_THRESHOLD 2400
/*
* Check, if transmit buffers are processed
@@ -505,7 +505,7 @@
pr_debug("CPM uart[%d]:set_termios\n", port->line);
baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk / 16);
- if (baud <= HW_BUF_SPD_THRESHOLD ||
+ if (baud < HW_BUF_SPD_THRESHOLD ||
(pinfo->port.state && pinfo->port.state->port.tty->low_latency))
pinfo->rx_fifosize = 1;
else
--
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