On Mon, 2017-04-24 at 12:30 +0200, Jan Kiszka wrote:
> After migrating 8250_exar to MSI in 172c33cb61da, we can get stuck
> without further interrupts because of the special wake-up event these
> chips send. They are only cleared by reading INT0. As we fail to do so
> during startup and shutdown, we can leave the interrupt line asserted,
> which is fatal with edge-triggered MSIs.
>
> Add the required reading of INT0 to startup and shutdown. Also account
> for the fact that a pending wake-up interrupt means we have to return
> 1
> from exar_handle_irq. Drop the unneeded reading of INT1..3 along with
> this - those never reset anything.
>
> An alternative approach would have been disabling the wake-up
> interrupt.
> Unfortunately, this feature (REGB[17] = 1) is not available on the
> XR17D15X.
FWIW:
Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
>
> Fixes: 172c33cb61da ("serial: exar: Enable MSI support")
> Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
> ---
>
> Changes in v2:
> - mention removal of INT1..3 reading in commit log [Andy]
> (no functional changes)
>
> drivers/tty/serial/8250/8250_port.c | 19 ++++++++++---------
> 1 file changed, 10 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/tty/serial/8250/8250_port.c
> b/drivers/tty/serial/8250/8250_port.c
> index 6119516ef5fc..3a3667880fcf 100644
> --- a/drivers/tty/serial/8250/8250_port.c
> +++ b/drivers/tty/serial/8250/8250_port.c
> @@ -47,6 +47,7 @@
> /*
> * These are definitions for the Exar XR17V35X and XR17(C|D)15X
> */
> +#define UART_EXAR_INT0 0x80
> #define UART_EXAR_SLEEP 0x8b /* Sleep mode */
> #define UART_EXAR_DVID 0x8d /* Device
> identification */
>
> @@ -1869,17 +1870,13 @@ static int
> serial8250_default_handle_irq(struct uart_port *port)
> static int exar_handle_irq(struct uart_port *port)
> {
> unsigned int iir = serial_port_in(port, UART_IIR);
> - int ret;
> + int ret = 0;
>
> - ret = serial8250_handle_irq(port, iir);
> + if (((port->type == PORT_XR17V35X) || (port->type ==
> PORT_XR17D15X)) &&
> + serial_port_in(port, UART_EXAR_INT0) != 0)
> + ret = 1;
>
> - if ((port->type == PORT_XR17V35X) ||
> - (port->type == PORT_XR17D15X)) {
> - serial_port_in(port, 0x80);
> - serial_port_in(port, 0x81);
> - serial_port_in(port, 0x82);
> - serial_port_in(port, 0x83);
> - }
> + ret |= serial8250_handle_irq(port, iir);
>
> return ret;
> }
> @@ -2177,6 +2174,8 @@ int serial8250_do_startup(struct uart_port
> *port)
> serial_port_in(port, UART_RX);
> serial_port_in(port, UART_IIR);
> serial_port_in(port, UART_MSR);
> + if ((port->type == PORT_XR17V35X) || (port->type ==
> PORT_XR17D15X))
> + serial_port_in(port, UART_EXAR_INT0);
>
> /*
> * At this point, there's no way the LSR could still be 0xff;
> @@ -2335,6 +2334,8 @@ int serial8250_do_startup(struct uart_port
> *port)
> serial_port_in(port, UART_RX);
> serial_port_in(port, UART_IIR);
> serial_port_in(port, UART_MSR);
> + if ((port->type == PORT_XR17V35X) || (port->type ==
> PORT_XR17D15X))
> + serial_port_in(port, UART_EXAR_INT0);
> up->lsr_saved_flags = 0;
> up->msr_saved_flags = 0;
>
--
Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Intel Finland Oy
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