[PATCH] Serial: Mobility's 16550A ports need a helping hand
The Mobility 16550A serial ports don't behave the same as standard
16550A ports, and need a helping hand to get them going once the
transmitter has drained and been disabled.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index 27cc288..341c644 100644
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -1027,6 +1027,8 @@
}
}
+static void transmit_chars(struct uart_8250_port *up);
+
static void serial8250_start_tx(struct uart_port *port, unsigned int tty_start)
{
struct uart_8250_port *up = (struct uart_8250_port *)port;
@@ -1034,6 +1036,14 @@
if (!(up->ier & UART_IER_THRI)) {
up->ier |= UART_IER_THRI;
serial_out(up, UART_IER, up->ier);
+
+ if (up->capabilities & UART_BUG_TXEN) {
+ unsigned char lsr, iir;
+ lsr = serial_in(up, UART_LSR);
+ iir = serial_in(up, UART_IIR);
+ if (lsr & UART_LSR_TEMT && iir & UART_IIR_NO_INT)
+ transmit_chars(up);
+ }
}
/*
* We only do this from uart_start
@@ -1439,6 +1449,7 @@
{
struct uart_8250_port *up = (struct uart_8250_port *)port;
unsigned long flags;
+ unsigned char lsr, iir;
int retval;
up->capabilities = uart_config[up->port.type].flags;
@@ -1542,6 +1553,26 @@
up->port.mctrl |= TIOCM_OUT2;
serial8250_set_mctrl(&up->port, up->port.mctrl);
+
+ /*
+ * Do a quick test to see if we receive an
+ * interrupt when we enable the TX irq.
+ */
+ serial_outp(up, UART_IER, UART_IER_THRI);
+ lsr = serial_in(up, UART_LSR);
+ iir = serial_in(up, UART_IIR);
+ serial_outp(up, UART_IER, 0);
+
+ if (lsr & UART_LSR_TEMT && iir & UART_IIR_NO_INT) {
+ if (!(up->capabilities & UART_BUG_TXEN)) {
+ up->capabilities |= UART_BUG_TXEN;
+ pr_debug("ttyS%d - enabling bad tx status workarounds\n",
+ port->line);
+ }
+ } else {
+ up->capabilities &= ~UART_BUG_TXEN;
+ }
+
spin_unlock_irqrestore(&up->port.lock, flags);
/*
diff --git a/drivers/serial/8250.h b/drivers/serial/8250.h
index cd5c3dd..9225c82 100644
--- a/drivers/serial/8250.h
+++ b/drivers/serial/8250.h
@@ -52,6 +52,7 @@
#define UART_CAP_UUE (1 << 12) /* UART needs IER bit 6 set (Xscale) */
#define UART_BUG_QUOT (1 << 0) /* UART has buggy quot LSB */
+#define UART_BUG_TXEN (1 << 1) /* UART has buggy TX IIR status */
#if defined(__i386__) && (defined(CONFIG_M386) || defined(CONFIG_M486))
#define _INLINE_ inline
