[PATCH v3 1/4] serial: 8250_dw: select port setup through platform data

[Andy Shevchenko]

On Sat, Oct 24, 2026 at 02:22:23PM -0600, James Hilliard wrote:
> Select feature discovery and DMA attachment through a platform-data setup
> callback. The generic callback probes the optional registers and attaches
> DMA when a FIFO size is available. Integrations with a fixed configuration
> can supply their own setup before the port is registered.
> 
> Replace skip_autocfg with the Octeon setup selection. On 64-bit builds,
> Octeon continues to skip optional-register probing while retaining its DMA
> setup; on 32-bit builds it retains the generic setup. Keep generic setup
> for devices without matched platform data as well.

...

> +static void dw8250_setup_dma(struct uart_port *p)
> +{
> +	struct dw8250_data *data = to_dw8250_data(p->private_data);
> +	struct uart_8250_port *up = up_to_u8250p(p);

> +	/* If we have a valid fifosize, try hooking up DMA */
> +	if (p->fifosize) {

This can be written now as

	/* We can't setup DMA when there is no FIFO defined */
	if (!p->fifosize)
		return;

> +		data->data.dma.rxconf.src_maxburst = p->fifosize / 4;
> +		data->data.dma.txconf.dst_maxburst = p->fifosize / 4;
> +		up->dma = &data->data.dma;
> +	}
> +}

...

> +	if (data->pdata) {
> +		if (data->pdata->setup)
> +			data->pdata->setup(p);

Do we have users for this case, when pdata is defined and no setup is provided?
What I see, we may default it to dw8250_setup() and drop a lot of assignments
below.  Otherwise those special cases can add an empty stubs, which in my opinion
will be cleaner solution.

> +	} else {
> +		dw8250_setup(p);
>  	}

...

>  static const struct dw8250_platform_data dw8250_octeon_3860_data = {
>  	.usr_reg = OCTEON_UART_USR,
>  	.quirks = DW_UART_QUIRK_OCTEON,
> +#ifdef CONFIG_64BIT
> +	.setup = dw8250_setup_dma,
> +#else
> +	.setup = dw8250_setup,
> +#endif

I'm wondering if we can do something at runtime with these ugly ifdef:s
(yes, it's a preexisted inconvenience).

>  };

-- 
With Best Regards,
Andy Shevchenko