Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1167257AbdDXI7v (ORCPT ); Mon, 24 Apr 2017 04:59:51 -0400 Received: from mga14.intel.com ([192.55.52.115]:39475 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761363AbdDXI7m (ORCPT ); Mon, 24 Apr 2017 04:59:42 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.37,243,1488873600"; d="scan'208";a="252695334" Message-ID: <1493024379.24567.154.camel@linux.intel.com> Subject: Re: [PATCH] serial: exar: Fix stuck MSIs From: Andy Shevchenko To: Jan Kiszka , Greg Kroah-Hartman Cc: Linux Kernel Mailing List , linux-serial@vger.kernel.org, Sudip Mukherjee Date: Mon, 24 Apr 2017 11:59:39 +0300 In-Reply-To: <39750541-c6a9-0e49-59fa-9f0a2e202850@web.de> References: <39750541-c6a9-0e49-59fa-9f0a2e202850@web.de> Organization: Intel Finland Oy Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.22.6-1 Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3317 Lines: 100 On Sat, 2017-04-22 at 11:36 +0200, Jan Kiszka wrote: > From: Jan Kiszka > > 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. > > An alternative approach would have been disabling the wake-up > interrupt. > Unfortunately, this feature (REGB[17] = 1) is not available on the > XR17D15X. > > Fixes: 172c33cb61da ("serial: exar: Enable MSI support") > Signed-off-by: Jan Kiszka > --- > > Regression of upcoming 4.11. > >  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); You replaced 4 reads by one. I'm suspecting that on multi-port cards you still need to read all of them (I assume they are called INT0, INT1, ...). Perhaps you need a helper where you do that and call it from all necessary places. > - } > + 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 Intel Finland Oy