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

[Jia Wang]

On 2026-04-17 10:46 +0300, Andy Shevchenko wrote:
> 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?
>

Thanks for the feedback.

I will switch to using DW_UART_QUIRK_CPR_VALUE in v3.
 
> -- 
> With Best Regards,
> Andy Shevchenko
> 
> 
>

Best Regards,
Jia Wang