From: Jan Kiszka <jan.kiszka@web.de>
To: Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-serial@vger.kernel.org,
Sudip Mukherjee <sudip.mukherjee@codethink.co.uk>
Subject: Re: [PATCH] serial: exar: Fix stuck MSIs
Date: Mon, 24 Apr 2017 11:06:17 +0200 [thread overview]
Message-ID: <d227c786-24eb-5acb-777d-02bd28d14254@web.de> (raw)
In-Reply-To: <1493024379.24567.154.camel@linux.intel.com>
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On 2017-04-24 10:59, Andy Shevchenko wrote:
> On Sat, 2017-04-22 at 11:36 +0200, Jan Kiszka wrote:
>> From: Jan Kiszka <jan.kiszka@siemens.com>
>>
>> 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 <jan.kiszka@siemens.com>
>> ---
>>
>> 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.
Nope, we never had to read them all: "Wake-up Indicator is cleared by
reading the INT0 register." (Exar manual) INT0 contains the interrupt
status for all channels.
Jan
>
>> - }
>> + 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;
>>
>
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next prev parent reply other threads:[~2017-04-24 9:07 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-22 9:36 [PATCH] serial: exar: Fix stuck MSIs Jan Kiszka
2017-04-24 8:59 ` Andy Shevchenko
2017-04-24 9:06 ` Jan Kiszka [this message]
2017-04-24 9:45 ` Andy Shevchenko
2017-04-24 10:30 ` [PATCH v2] " Jan Kiszka
2017-04-24 12:07 ` Andy Shevchenko
2017-05-13 7:09 ` Jan Kiszka
2017-05-14 11:32 ` Greg Kroah-Hartman
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