Am 13.12.18 um 08:44 schrieb Rouven Czerwinski:
> According to the device tree bindings for 8250, width is an optional property.
> Default to 1 which is the same default value as used by the kernel.
> Before this change the driver would not work for device trees which do not
> include the optional binding.
> 
> Signed-off-by: Rouven Czerwinski <r.czerwinski@pengutronix.de>
> ---
>  drivers/serial/serial_ns16550.c | 46 ++++++++++++++++-----------------
>  1 file changed, 23 insertions(+), 23 deletions(-)
> 
> diff --git a/drivers/serial/serial_ns16550.c b/drivers/serial/serial_ns16550.c
> index 4d73ea8b8..8ddcfdbef 100644
> --- a/drivers/serial/serial_ns16550.c
> +++ b/drivers/serial/serial_ns16550.c
> @@ -297,36 +297,36 @@ static int ns16550_tstc(struct console_device *cdev)
>  static void ns16550_probe_dt(struct device_d *dev, struct ns16550_priv *priv)
>  {
>  	struct device_node *np = dev->device_node;
> -	u32 width;
> +	u32 width = 1;
>  
>  	if (!IS_ENABLED(CONFIG_OFDEVICE))
>  		return;
>  
>  	of_property_read_u32(np, "clock-frequency", &priv->plat.clock);
>  	of_property_read_u32(np, "reg-shift", &priv->plat.shift);
> -	if (!of_property_read_u32(np, "reg-io-width", &width))
> -		switch (width) {
> -		case 1:
> -			priv->read_reg = ns16550_read_reg_mmio_8;
> -			priv->write_reg = ns16550_write_reg_mmio_8;
> -			break;
> -		case 2:
> -			priv->read_reg = ns16550_read_reg_mmio_16;
> -			priv->write_reg = ns16550_write_reg_mmio_16;
> -			break;
> -		case 4:
> -			if (of_device_is_big_endian(np)) {
> -				priv->read_reg = ns16550_read_reg_mmio_32be;
> -				priv->write_reg = ns16550_write_reg_mmio_32be;
> -			} else {
> -				priv->read_reg = ns16550_read_reg_mmio_32;
> -				priv->write_reg = ns16550_write_reg_mmio_32;
> -			}
> -			break;
> -		default:
> -			dev_err(dev, "unsupported reg-io-width (%d)\n",
> -				width);
> +	of_property_read_u32(np, "reg-io-width", &width);

i think it is not good to drop error handling completely. We may fail in
different ways:
static const void *of_find_property_value_of_size(const struct
device_node *np,
			const char *propname, u32 len)
{
	struct property *prop = of_find_property(np, propname, NULL);
	const void *value;

	if (!prop)
		return ERR_PTR(-EINVAL);
	value = of_property_get_value(prop);
	if (!value)
		return ERR_PTR(-ENODATA);
	if (len > prop->length)
		return ERR_PTR(-EOVERFLOW);

	return value;
}


> +	switch (width) {
> +	case 1:
> +		priv->read_reg = ns16550_read_reg_mmio_8;
> +		priv->write_reg = ns16550_write_reg_mmio_8;
> +		break;
> +	case 2:
> +		priv->read_reg = ns16550_read_reg_mmio_16;
> +		priv->write_reg = ns16550_write_reg_mmio_16;
> +		break;
> +	case 4:
> +		if (of_device_is_big_endian(np)) {
> +			priv->read_reg = ns16550_read_reg_mmio_32be;
> +			priv->write_reg = ns16550_write_reg_mmio_32be;
> +		} else {
> +			priv->read_reg = ns16550_read_reg_mmio_32;
> +			priv->write_reg = ns16550_write_reg_mmio_32;
>  		}
> +		break;
> +	default:
> +		dev_err(dev, "unsupported reg-io-width (%d)\n",
> +			width);
> +	}
>  }
>  
>  static struct ns16550_drvdata ns16450_drvdata = {
> 


-- 
Regards,
Oleksij