Re: [PATCH v2 0/6] hw/char: Implement the STM32L4x5 USART, UART and LPUART

[Peter Maydell <peter.maydell@linaro.org>]

On Sun, 24 Mar 2024 at 16:56, Arnaud Minier
<arnaud.minier@telecom-paris.fr> wrote:
>
> This patch adds the STM32L4x5 USART
> (Universal Synchronous/Asynchronous Receiver/Transmitter)
> device and is part of a series implementing the
> STM32L4x5 with a few peripherals.
>
> It implements the necessary functionalities to receive/send
> characters over the serial port, which are useful to
> communicate with the program currently running.
>
> Many thanks Peter for your review, I think I addressed almost
> everything.
> I'm just unsure about how to handle the waiting time in the tests.
> I understand your concerns about the unreliability of using the wallclock
> time but I don't understand how using clock_step() would make it
> more reliable. We will always be waiting on something
> that is out of our control (i.e. the OS).
> I increased the delay from 5s to 10min to match the microbit test
> and added a comment (I paraphrased your comment, is that okay ?).

I think I was slightly confused between two things. For
a lot of qtests we do want to use clock_step() and not
have wallclock-based delays, but we can only do that where
the thing we're waiting for is purely simulation time
(i.e. where we triggered a change via a qtest write and
then want to look for the result via a qtest read).
Where we're triggering something via a different OS
pathway (e.g. here where we write to the socket that's
backing the chardev connected to the UART and then look
at the UART registers) we do need a wallclock delay.

I recommend you follow Thomas's suggestions about timeouts
in his comments on patch 6; I'd forgotten we have a
meson timeout now too.

thanks
-- PMM