Re: [Qemu-devel] [PATCH v27 5/8] target/avr: Add limited support for USART and 16 bit timer peripherals

["Pavel Dovgalyuk" <dovgaluk@ispras.ru>]

> From: Qemu-devel [mailto:qemu-devel-bounces+patchwork-qemu-
> devel=patchwork.kernel.org@nongnu.org] On Behalf Of Michael Rolnik
> From: Sarah Harris <S.E.Harris@kent.ac.uk>
> 
> These were designed to facilitate testing but should provide enough function to be useful in
> other contexts.

USART is very useful for testing, but to which model of AVR is belongs?
We also started implementation of USART and other devices in our internship program,
using prior version of your patches.
There were other register addresses for the registers and some of them even intersect
making read/write logic more complex (we looked at Atmega8).

You also mix the board and the SoC into one file, making hardware-on-chip harder to reuse.

I think that the structure can be revised in the following way:
Board -> SoC -> Devices

Board includes SoC, loads the firmware, and adds some external peripheral devices, if needed.

SoC includes embedded peripherals. It dispatches IO memory accesses and passes them
to the devices. In this case you can have different register addresses for different SoCs, but
the embedded device emulation code can be mostly the same for simple devices like USART.

> Only a subset of the functions of each peripheral is implemented, mainly due to the lack of a
> standard way to handle electrical connections (like GPIO pins).

We did not got too much results, you can check for our changes here: https://github.com/Dovgalyuk/qemu/tree/avr8

But we can help you in development of better version of the patches and split the work
for making this platform more usable.


Pavel Dovgalyuk