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tty/serial/core: Introduce poll_init callback

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It was noticed that polling drivers (like KGDB) are not able to use
serial ports if the ports were not previously initialized via console.
I.e.  when booting with console=ttyAMA0 kgdboc=ttyAMA0, everything works
fine, but with console=ttyFOO kgdboc=ttyAMA0, the kgdboc doesn't work.

This is because we don't initialize the hardware. Calling ->startup() is
not an option, because drivers request interrupts there, and drivers
fail to handle situations when tty isn't opened with interrupts enabled.

So, we have to implement a new callback (actually, tty_ops already have
a similar callback), which does everything needed to initialize just the
hardware.

Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Anton Vorontsov 2012-09-24 14:27:53 -07:00 committed by Greg Kroah-Hartman
parent 729043e82c
commit c7f3e7087a
2 changed files with 18 additions and 0 deletions
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17
drivers/tty/serial/serial_core.c
View file

@ -2129,6 +2129,7 @@ static int uart_poll_init(struct tty_driver *driver, int line, char *options)
int bits = 8;
int parity = 'n';
int flow = 'n';
int ret;
if (!state || !state->uart_port)
return -1;
@ -2137,6 +2138,22 @@ static int uart_poll_init(struct tty_driver *driver, int line, char *options)
if (!(port->ops->poll_get_char && port->ops->poll_put_char))
return -1;
if (port->ops->poll_init) {
struct tty_port *tport = &state->port;
ret = 0;
mutex_lock(&tport->mutex);
/*
* We don't set ASYNCB_INITIALIZED as we only initialized the
* hw, e.g. state->xmit is still uninitialized.
*/
if (!test_bit(ASYNCB_INITIALIZED, &tport->flags))
ret = port->ops->poll_init(port);
mutex_unlock(&tport->mutex);
if (ret)
return ret;
}
if (options) {
uart_parse_options(options, &baud, &parity, &bits, &flow);
return uart_set_options(port, NULL, baud, parity, bits, flow);

1
include/linux/serial_core.h
View file

@ -275,6 +275,7 @@ struct uart_ops {
int (*verify_port)(struct uart_port *, struct serial_struct *);
int (*ioctl)(struct uart_port *, unsigned int, unsigned long);
#ifdef CONFIG_CONSOLE_POLL
int (*poll_init)(struct uart_port *);
void (*poll_put_char)(struct uart_port *, unsigned char);
int (*poll_get_char)(struct uart_port *);
#endif