[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>
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@ -1027,6 +1027,8 @@ static void serial8250_stop_tx(struct uart_port *port, unsigned int tty_stop)
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}
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}
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static void transmit_chars(struct uart_8250_port *up);
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static void serial8250_start_tx(struct uart_port *port, unsigned int tty_start)
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{
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struct uart_8250_port *up = (struct uart_8250_port *)port;
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@ -1034,6 +1036,14 @@ static void serial8250_start_tx(struct uart_port *port, unsigned int tty_start)
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if (!(up->ier & UART_IER_THRI)) {
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up->ier |= UART_IER_THRI;
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serial_out(up, UART_IER, up->ier);
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if (up->capabilities & UART_BUG_TXEN) {
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unsigned char lsr, iir;
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lsr = serial_in(up, UART_LSR);
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iir = serial_in(up, UART_IIR);
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if (lsr & UART_LSR_TEMT && iir & UART_IIR_NO_INT)
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transmit_chars(up);
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}
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}
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/*
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* We only do this from uart_start
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@ -1439,6 +1449,7 @@ static int serial8250_startup(struct uart_port *port)
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{
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struct uart_8250_port *up = (struct uart_8250_port *)port;
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unsigned long flags;
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unsigned char lsr, iir;
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int retval;
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up->capabilities = uart_config[up->port.type].flags;
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@ -1542,6 +1553,26 @@ static int serial8250_startup(struct uart_port *port)
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up->port.mctrl |= TIOCM_OUT2;
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serial8250_set_mctrl(&up->port, up->port.mctrl);
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/*
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* Do a quick test to see if we receive an
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* interrupt when we enable the TX irq.
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*/
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serial_outp(up, UART_IER, UART_IER_THRI);
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lsr = serial_in(up, UART_LSR);
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iir = serial_in(up, UART_IIR);
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serial_outp(up, UART_IER, 0);
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if (lsr & UART_LSR_TEMT && iir & UART_IIR_NO_INT) {
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if (!(up->capabilities & UART_BUG_TXEN)) {
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up->capabilities |= UART_BUG_TXEN;
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pr_debug("ttyS%d - enabling bad tx status workarounds\n",
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port->line);
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}
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} else {
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up->capabilities &= ~UART_BUG_TXEN;
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}
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spin_unlock_irqrestore(&up->port.lock, flags);
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/*
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@ -52,6 +52,7 @@ struct serial8250_config {
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#define UART_CAP_UUE (1 << 12) /* UART needs IER bit 6 set (Xscale) */
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#define UART_BUG_QUOT (1 << 0) /* UART has buggy quot LSB */
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#define UART_BUG_TXEN (1 << 1) /* UART has buggy TX IIR status */
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#if defined(__i386__) && (defined(CONFIG_M386) || defined(CONFIG_M486))
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#define _INLINE_ inline
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