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SubjectRe: UART/TTY console deadlock
On (20/06/30 11:02), Tony Lindgren wrote:
> This conditional disable for irq_shared does not look nice to me
> from the other device point of view :)
>
> Would it be possible to just set up te dummy interrupt handler
> for the startup, then change it back afterwards? See for example
> omap8250_no_handle_irq().

I think we can do it. serial8250_do_startup() and irq handler take
port->lock, so they should be synchronized.

Something like this then?

---

diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index f77bf820b7a3..61ad6f5f0f88 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -2140,6 +2140,11 @@ static void serial8250_put_poll_char(struct uart_port *port,

#endif /* CONFIG_CONSOLE_POLL */

+static int serial8250_dummy_handle_irq(struct uart_port *port)
+{
+ return 0;
+}
+
int serial8250_do_startup(struct uart_port *port)
{
struct uart_8250_port *up = up_to_u8250p(port);
@@ -2271,6 +2276,9 @@ int serial8250_do_startup(struct uart_port *port)

if (port->irq && !(up->port.flags & UPF_NO_THRE_TEST)) {
unsigned char iir1;
+ int (*handler)(struct uart_port *);
+
+ handler = port->handle_irq;
/*
* Test for UARTs that do not reassert THRE when the
* transmitter is idle and the interrupt has already
@@ -2280,8 +2288,7 @@ int serial8250_do_startup(struct uart_port *port)
* allow register changes to become visible.
*/
spin_lock_irqsave(&port->lock, flags);
- if (up->port.irqflags & IRQF_SHARED)
- disable_irq_nosync(port->irq);
+ port->handle_irq = serial8250_dummy_handle_irq;

wait_for_xmitr(up, UART_LSR_THRE);
serial_port_out_sync(port, UART_IER, UART_IER_THRI);
@@ -2293,8 +2300,7 @@ int serial8250_do_startup(struct uart_port *port)
iir = serial_port_in(port, UART_IIR);
serial_port_out(port, UART_IER, 0);

- if (port->irqflags & IRQF_SHARED)
- enable_irq(port->irq);
+ port->handle_irq = handler;
spin_unlock_irqrestore(&port->lock, flags);

/*
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