Subject: Re: [PATCH 2/3] [POWERPC][V3] Xilinx: of_serial support for Xilinx uart 16550.

From: Sergei Shtylyov <[email-masked]>
Date: Thu, 03 Apr 2008 16:25:30 +0400

Hello.

John Linn wrote:

> The Xilinx 16550 uart core is not a standard 16550 because it uses
> word-based addressing rather than byte-based addressing. With
> additional properties it is compatible with the open firmware
> 'ns16550' compatible binding.

> This code updates the of_serial driver to handle the reg-offset
> and reg-shift properties to enable this core to be used.

> Signed-off-by: John Linn <[email-masked]>
> ---

> diff --git a/drivers/serial/of_serial.c b/drivers/serial/of_serial.c
> index 2efb892..73c47a5 100644
> --- a/drivers/serial/of_serial.c
> +++ b/drivers/serial/of_serial.c
> @@ -31,7 +31,8 @@ static int __devinit of_platform_serial_setup(struct of_device *ofdev,
>  	struct resource resource;
>  	struct device_node *np = ofdev->node;
>  	const unsigned int *clk, *spd;
> -	int ret;
> +	const u32 *prop;
> +	int ret, prop_size;
>  
>  	memset(port, 0, sizeof *port);
>  	spd = of_get_property(np, "current-speed", NULL);
> @@ -49,6 +50,17 @@ static int __devinit of_platform_serial_setup(struct of_device *ofdev,
>  
>  	spin_lock_init(&port->lock);
>  	port->mapbase = resource.start;
> +
> +	/* Check for shifted address mapping */
> +	prop = of_get_property(np, "reg-offset", &prop_size);
> +	if (prop && (prop_size == sizeof(u32)))
> +		port->mapbase += *prop;

    I disagree. That trick leads to I/O resource misaccounting/misreporting. 
You should teach 8250.c about the offset trick instead, just as it's been 
taught the shift trick in its time.

> +
> +	/* Check for registers offset within the devices address range */
> +	prop = of_get_property(np, "reg-shift", &prop_size);
> +	if (prop && (prop_size == sizeof(u32)))
> +		port->regshift = *prop;
> +
>  	port->irq = irq_of_parse_and_map(np, 0);
>  	port->iotype = UPIO_MEM;
>  	port->type = type;

WBR, Sergei