Re: [PATCH v3 2/2] serial: 8250_dw: Use a fixed CPR value for UltraRISC DP1000 UART

[Jia Wang <wangjia@ultrarisc.com>]

On 2026-04-22 12:01 +0300, Ilpo Järvinen wrote:
> On Wed, 22 Apr 2026, Jia Wang wrote:
> 
> > On 2026-04-21 15:18 +0300, Ilpo Järvinen wrote:
> > > On Tue, 21 Apr 2026, Jia Wang wrote:
> > > 
> > > > The UltraRISC DP1000 UART does not provide the standard CPR register used
> > > > by 8250_dw to discover port capabilities.
> > > > 
> > > > Provide a fixed CPR value for the DP1000-specific compatible so the
> > > > driver can configure the port correctly.
> > > > 
> > > > Signed-off-by: Jia Wang <wangjia@ultrarisc.com>
> > > > ---
> > > >  drivers/tty/serial/8250/8250_dw.c | 7 +++++++
> > > >  1 file changed, 7 insertions(+)
> > > > 
> > > > diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
> > > > index 94beadb4024d..ca6dbdf75918 100644
> > > > --- a/drivers/tty/serial/8250/8250_dw.c
> > > > +++ b/drivers/tty/serial/8250/8250_dw.c
> > > > @@ -962,6 +962,12 @@ static const struct dw8250_platform_data dw8250_intc10ee = {
> > > >  	.quirks = DW_UART_QUIRK_IER_KICK,
> > > >  };
> > > >  
> > > > +static const struct dw8250_platform_data dw8250_ultrarisc_dp1000_data = {
> > > > +	.usr_reg = DW_UART_USR,
> > > > +	.cpr_value = 0x00022022,
> > > 
> > > Hi,
> > > 
> > > Please construct the cpr_value by ORing DW_UART_CPR_* defines together.
> > > For fields, FIELD_PREP_CONST() may be useful.
> > > 
> > > In order to be able to use the DW_UART_CPR_* defines, they need to be 
> > > moved into 8250_dwlib.h (I'd move all DW_UART register defines in a 
> > > preparatory patch).
> > > 
> > > I know the existing Renesas' .cpr_value doesn't follow this convention but 
> > > that could be converted as well (in another patch, or leave the Renesas 
> > > entry conversion to me if you don't want to do that).
> > >
> > 
> > Thanks for the review.
> > 
> > Just to confirm: since you mentioned that the preparatory patch moving
> > the DW_UART register defines is already in place, I don't need to move
> > them again, correct?
> 
> I'm not sure where that preparatory patch is. Those defines still appear 
> in 8250_dwlib.c AFAICT.
> 
> To be clear, DW_UART_CPR_* defines are in 8250_dwlib.c but you're 
> modifying 8250_dw.c file here so you cannot use those pre-existing defines 
> as is in 8250_dw.c. To solve that, please add a preparatory patch into 
> your series which relocates all those defines from 8250_dwlib.c to 
> 8250_dwlib.h. If there's a patch which does that already, it has missed my 
> radar.
> 
> And my suggestion is to move not just DW_UART_CPR_* defines into 
> 8250_dwlib.h but all DW UART specific register defines to keep them in 
> the same place.
> 
> Hopefully this clears up any misunderstanding.
> 
> 
> My main point all along is that do not do the define move in the same 
> patch where you're adding UltraRISC DP1000 UART (which is a common pitfall 
> to many submitters so I try to give pro-active instructions while 
> reviewing to avoid extra versions because of them).
>

Thanks.

Understood. I will add a preparatory patch to move all DW_UART register
defines into 8250_dwlib.h, and update the UltraRISC DP1000 support accordingly.

I will also follow the ordering suggested during review and resend the
series as v4.
 
> > I will update my patch to use the DW_UART_CPR_* macros and
> > FIELD_PREP_CONST() accordingly, and I’m happy to add a separate patch in
> > the next revision to convert the Renesas .cpr_value as well.
> 
> Great, thanks.
> 
> > > > +	.quirks = DW_UART_QUIRK_CPR_VALUE,
> > > > +};
> 
> -- 
>  i.

Regards,
Jia Wang