[PATCH v7 4/4] serial: 8250_dw: Use a fixed CPR value for UltraRISC DP1000 UART

[Jia Wang]

On 2026-04-29 13:55 +0300, Ilpo Järvinen wrote:
> On Wed, 29 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 at ultrarisc.com>
> > Reviewed-by: Andy Shevchenko <andriy.shevchenko at linux.intel.com>
> > ---
> >  drivers/tty/serial/8250/8250_dw.c | 10 ++++++++++
> >  1 file changed, 10 insertions(+)
> > 
> > diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
> > index 480f82d89856..55e40c10f46a 100644
> > --- a/drivers/tty/serial/8250/8250_dw.c
> > +++ b/drivers/tty/serial/8250/8250_dw.c
> > @@ -959,6 +959,15 @@ 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 = FIELD_PREP_CONST(DW_UART_CPR_ABP_DATA_WIDTH, 2) |
> > +		     DW_UART_CPR_THRE_MODE |
> > +		     DW_UART_CPR_DMA_EXTRA |
> > +		     DW_UART_CPR_FIFO_MODE_FROM_SIZE(32),
> > +	.quirks = DW_UART_QUIRK_CPR_VALUE,
> 
> Thanks for all the effort you put to this series,
> 
> Reviewed-by: Ilpo Järvinen <ilpo.jarvinen at linux.intel.com>
> 
> Unrelated to this patch, I suppose we wouldn't strictly need to have 
> DW_UART_QUIRK_CPR_VALUE in this driver as non-zero .cpr_value should be 
> enough to decide if the CPR quirk should be used or not (if the code is 
> adapted, obviously).
> 

Thanks for the review and the tag, Ilpo.

The idea of dropping the quirk flag sounds reasonable to me. I'll keep
it in mind for a future cleanup patch once this series is merged.

> > +};
> > +
> >  static const struct of_device_id dw8250_of_match[] = {
> >  	{ .compatible = "snps,dw-apb-uart", .data = &dw8250_dw_apb },
> >  	{ .compatible = "cavium,octeon-3860-uart", .data = &dw8250_octeon_3860_data },
> > @@ -966,6 +975,7 @@ static const struct of_device_id dw8250_of_match[] = {
> >  	{ .compatible = "renesas,rzn1-uart", .data = &dw8250_renesas_rzn1_data },
> >  	{ .compatible = "sophgo,sg2044-uart", .data = &dw8250_skip_set_rate_data },
> >  	{ .compatible = "starfive,jh7100-uart", .data = &dw8250_skip_set_rate_data },
> > +	{ .compatible = "ultrarisc,dp1000-uart", .data = &dw8250_ultrarisc_dp1000_data },
> >  	{ /* Sentinel */ }
> >  };
> >  MODULE_DEVICE_TABLE(of, dw8250_of_match);
> > 
> > 
> 
> -- 
>  i.

Best Regards,
Jia Wang