lkml.org 
[lkml]   [2017]   [Apr]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v2] serial: exar: Fix stuck MSIs
From
Date
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@linux.intel.com>

>
> Fixes: 172c33cb61da ("serial: exar: Enable MSI support")
> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> ---
>
> 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@linux.intel.com>
Intel Finland Oy

\
 
 \ /
  Last update: 2017-04-24 14:08    [W:0.148 / U:0.156 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site