Re: [PATCH v3 1/3] hw/char: add K230 DW 8250-compatible UART

On 8/15/26 21:57, Philippe Mathieu-Daudé wrote:
> How much this diverges of the generic 8250 model we have?
>
> In order to reduce maintenance burden with duplicated code, the
> project preference is to use the inheritance pattern of oriented
> bject programming, in particular with QOM APIs.
>
> This model could inherit from our generic model with:
>
>   TypeInfo::parent = TYPE_SERIAL
>
> then override its specific methods.
>
> Could you have a look and justify the full rewrite? 

Hi Phil,

Thanks for the review.

The rewrite was not meant as a replacement for the generic 8250. I
was following the K230 TRM as closely as I could, and I did not
realize the preferred approach was to reuse the in-tree 8250 via
QOM rather than reimplement the 16550 core.

I agree the duplication is not justified. I will respin this to
inherit from / reuse the generic serial model as you suggested,
and keep the DesignWare probe window that Linux 8250_dw needs
(UCV/CPR/CTR/DLF/USR).

One open question: the TRM (and CPR) advertise some DesignWare
extras beyond a plain 16550 — for example a 32-byte FIFO, THRE
mode, shadow registers, and USR busy-detect. The first version
implemented several of these, which is why it grew into a full
rewrite. For the respin, should I:

   1) keep only the minimal probe window (CPR not advertising
      features the generic model does not implement), or
   2) plan follow-up work to model some of those DW extras?

I am happy either way; I mainly want to know which level of
fidelity is good.

If the pending generic dw8250 lands first, I can also switch the
K230 board over to that type instead of keeping a parallel model.

Thanks,
WX Chen