Mark Lokowich <lokowich@xxxxxxxxxxx> writes:
> Philip Balister wrote:
>> Kevin Hilman wrote:
>>> Mark Lokowich <lokowich@xxxxxxxxxxx> writes:
>>>
>>>> Revert double IIR test in 8250 driver
>>>>
>>>
>>> Can you give a more detailed description of what the problem is that
>>> is being fixed?
>>
>> Without this patch, serial console behavior is strange. You type and
>> nothing is echoed and you hit return and things happen. It feels
>> like two processes are grabbing input.
>>
>> I think someone posted a more technical description, but I couldn't
>> find it quickly.
>>
>> Philip
>>
> This section of the driver is a test for faulty 16650
> implementations that require a backup timer. The patch reverts the
> change that compares two states (instead of one, as in 2.6.25.2) of
> the IIR to determine if the workaround is required. The DaVinci
> UART does not need the backup timer, but the double conditional
> passed, enabling the timer and causing interrupt handling errors on
> the console and other UARTS.
>
Thanks Mark,
Do you have any recommendations for ways to conditionalize this code
so the test still works on other platforms. Maybe via a new flag in
platform data?
I want to be sure there is a mainline-acceptable fix here, so we are
not divirging from mainline in generic code.
Kevin
>
>>
>>> This is in the generic 8250 driver so will affect all platforms. For
>>> this to be accepted, it should be discussed on linux-serial[1]
>>>
>>> Kevin
>>>
>>>> Acked-by: Jaswinder Singh <jaswinder@xxxxxxxxxxx>
>>>> ---
>>>> --- linux-2.6/drivers/serial/8250.c
>>>> +++ linux-2.6-vanilla/drivers/serial/8250.c
>>>> @@ -1867,7 +1867,6 @@
>>>> }
>>>>
>>>> if (is_real_interrupt(up->port.irq)) {
>>>> - unsigned char iir1;
>>>> /*
>>>> * Test for UARTs that do not reassert THRE when the
>>>> * transmitter is idle and the interrupt has already
>>>> @@ -1881,7 +1880,7 @@
>>>> wait_for_xmitr(up, UART_LSR_THRE);
>>>> serial_out_sync(up, UART_IER, UART_IER_THRI);
>>>> udelay(1); /* allow THRE to set */
>>>> - iir1 = serial_in(up, UART_IIR);
>>>> + serial_in(up, UART_IIR);
>>>> serial_out(up, UART_IER, 0);
>>>> serial_out_sync(up, UART_IER, UART_IER_THRI);
>>>> udelay(1); /* allow a working UART time to re-assert THRE */
>>>> @@ -1894,7 +1893,7 @@
>>>> * If the interrupt is not reasserted, setup a timer to
>>>> * kick the UART on a regular basis.
>>>> */
>>>> - if (!(iir1 & UART_IIR_NO_INT) && (iir & UART_IIR_NO_INT)) {
>>>> + if (iir & UART_IIR_NO_INT) {
>>>> pr_debug("ttyS%d - using backup timer\n", port->line);
>>>> up->timer.function = serial8250_backup_timeout;
>>>> up->timer.data = (unsigned long)up;
>>>>
>>>>
>>>> _______________________________________________
>>>> Davinci-linux-open-source mailing list
>>>> Davinci-linux-open-source@xxxxxxxxxxxxxxxxxxxx
>>>> http://linux.davincidsp.com/mailman/listinfo/davinci-linux-open-source
>>>
>>>
>>> [1] From MAINTAINERS:
>>>
>>> 8250/16?50 (AND CLONE UARTS) SERIAL DRIVER
>>> L: linux-serial@xxxxxxxxxxxxxxx
>>> W: http://serial.sourceforge.net
>>> S: Orphan
>>> _______________________________________________
>>> Davinci-linux-open-source mailing list
>>> Davinci-linux-open-source@xxxxxxxxxxxxxxxxxxxx
>>> http://linux.davincidsp.com/mailman/listinfo/davinci-linux-open-source
>>>
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