[PATCH v2 2/2] riscv: ultrarisc: 8250_dw: support DP1000 uart

[Jia Wang]

On 2026-03-16 13:35 +0200, Andy Shevchenko wrote:
> On Mon, Mar 16, 2026 at 02:33:23PM +0800, Jia Wang via B4 Relay wrote:
> 
> > The UART of DP1000 does not support automatic detection of
> > buffer size. skip_autocfg needs to be set to true
> 
> Missed period at the end.
> 

Thanks, I will fix the missing period.

> 
> ...
> 
> > +#define DW_UART_QUIRK_FIXED_TYPE	BIT(6)
> 
> Seems unrequired.
> 
> But to make sure, can you elaborate what's going on here?
> What is the reads from UCV and CPR registers?
>

Apologies for the delayed response.

Our DW UART implementation on DP1000 does not provide the CPR/UCV capability
registers, and reads from both registers always return 0. As a result, the
autodetection logic in 8250_dw cannot obtain meaningful capability
information.

To handle this, the current approach is to skip autodetection and rely on
fixed configuration via a quirk.

If there is a preferred or more appropriate way to support DW UART instances
without CPR/UCV, I would be happy to adjust the implementation based on your
suggestions.
 
> -- 
> With Best Regards,
> Andy Shevchenko
> 
> 
>

Best Regards,
Jia Wang