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[PATCH] Serial: Mobility's 16550A ports need a helping hand

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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>
This commit is contained in:
Russell King 2005-06-23 15:05:41 +01:00
parent 4ba5e35daa
commit 55d3b282b9
2 changed files with 32 additions and 0 deletions
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31
drivers/serial/8250.c
View File

@ -1027,6 +1027,8 @@ static void serial8250_stop_tx(struct uart_port *port, unsigned int tty_stop)
}
}
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 @@ static void serial8250_start_tx(struct uart_port *port, unsigned int tty_start)
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 @@ static int serial8250_startup(struct uart_port *port)
{
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 @@ static int serial8250_startup(struct uart_port *port)
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);
/*

1
drivers/serial/8250.h
View File

@ -52,6 +52,7 @@ struct serial8250_config {
#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