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

[Ilpo Järvinen]

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).

> +};
> +
>  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.