Re: [PATCH] serial 8250: tighten test for using backup timer

[Will Newton]

 On Tue, Aug 5, 2008 at 9:06 PM, Alex Williamson <alex.williamson@xxxxxx> wrote:
> Hi Will,
>
> On Tue, 2008-08-05 at 12:44 +0100, Will Newton wrote:
>> Hi,
>>
>> Sorry to not have picked up on this earlier, but this change seems to
>> break an old DesignWare UART I have in an SoC here. It has a number of
>> known issues, one of which is it does not appropriately reassert THRE.
>>
>> What seems to happen is that the first time the port is opened the
>> code tests for incorrect reassertion of THRE and correctly sets up the
>> backup timer. The port is closed and subsequently reopened and this
>> time around the new logic prevents the backup timer from being
>> enabled. I'm not 100% sure of the details of the bug that is being
>> worked around here, but it appears that the second time the port is
>> opened it is not possible to detect the bug because the previous THRE
>> condition has already been acknowledged.
>>
>> The attached patch fixes the problem for me and attempts to preserve
>> the new behaviour at the same time. Comments?
>
> It would be nice if there was a simple procedure we could do on the UART
> to reset it to a state so the test works repeatedly.  However, with all
> the buggy UARTs out there, that could end up disturbing someone else.
>
> This change works for me, though it is using up a bit in the bugs field;
> not that we seem to be allocating them at any great rate.  I think it
> would be worthy of a comment in the code to understand why this new
> block exists outside the test so we don't need to refer back to the
> commit changeset.
>
> Acked-by: Alex Williamson <alex.williamson@xxxxxx>

I've added a comment and your ack, thanks.

Andrew: Are you the appropriate person to send patches for the serial
subsystem to?