[U-Boot] [PATCH 0/2] [for 2018.03] RPi: Drain RX queue on setbrg

[Alexander Graf]

On 03/07/2018 02:07 PM, Peter Robinson wrote:
> On Tue, Mar 6, 2018 at 1:13 PM, Alexander Graf <agraf at suse.de> wrote:
>> We had a few reports coming in from people that had their autoboot chain
>> aborted after pinmuxing support was added for the RPi.
>>
>> The culprit is easy: The UARTs may have been enabled before, but muxed
>> to an incorrect pin. That pin may have pulled the RX line down which again
>> lead to lots of zero bytes gathered in the RX buffer.
>>
>> The easy fix for that is to drain the RX queue every time we set the baud
>> rate.
>>
>> This patch set is the minimally intrusive fix for the RPi. We may want to
>> do that generically for all serial devices later.
>>
>> Alexander Graf (2):
>>    serial_bcm283x_mu: Flush RX queue after setting baud rate
>>    bcm283x_pl011: Flush RX queue after setting baud rate
> This causes mixed effects for me, a regression on the RPi2 using the
> pl011, but fixes the issue on the RPi3. Both my RPi2 have serial
> console and playing with the enable in config.txt doesn't seem to have
> any effect on whether they auto boot or not but with it commented out
> I seem to get more random chars.

Thanks a lot for testing! I'll try it on a rpi2 later tonight and check 
why it's failing.


Alex