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

[Ilpo Järvinen]

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 at 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).

> +	.quirks = DW_UART_QUIRK_CPR_VALUE,
> +};
> +
>  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 },
> @@ -969,6 +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.