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

[Andy Shevchenko]

On Fri, Apr 17, 2026 at 03:32:17PM +0800, Jia Wang wrote:
> 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:

...

> > > +#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.

Why can't you provide a CPR value via the existing quirk?

-- 
With Best Regards,
Andy Shevchenko