[LTP] [PATCH 2/2] device_drivers/uart01: Add uart01 test

Cyril Hrubis chrubis@suse.cz
Thu Apr 2 11:31:27 CEST 2020

> >Indeed but it does not make sense tu run it with a different baud rates,
> >since the data are not transmitted at all.
> The data exchanged between Tx|Rx and buffer have nothing to do with
> baudrate?
> I think the baudrate is control Tx|Rx send and receive date rate to|from
> buffer.

That's what I'm not sure about, the documentation says that in loopback
mode data written to the port immediatelly appears on the receiving end,
which would mean that the uart speed does not matter at all.

Can you try a quick test? If you measure the time the test spends
writing data in loopback mode for a different uart speeds and they do
not differ the uart speed does not matter.

> >Unfortunately it does not seem to work on my AMD based desktop at all,
> >my guess is that the loopback bit is silently ignored by the hardware.
> >Which means that we cannot enable the test by default in loopback mode
> >after all
> I will test on my laptop and feedback result today, if it does no work , we
> should check the uart driver what different between x86 and arm64.

I bet that this differs chipset by chipset and I do not think there is
anything wrong with the uart driver per se.

Cyril Hrubis

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