RFC: MPC52xx serial port configuration from DT blob

[Dale Farnsworth]

Bartlomiej wrote:
> We have a MPC5200B-based board running an arch/powerpc kernel and we
> need the ability to configure a non-console serial port for a particular
> baud rate during system start-up. It seems that the UART driver in
> drivers/serial/mpc52xx_uart.c does not support this. It only allows to
> set parameters for a port that is used as a console, and for which those
> parameters are passed in the kernel command line. We would like to
> extend the mpc52xx_uart.c driver to be able to retrieve port options
> from the DT blob and configure a given port accordingly. A new
> port-specific property called "options" would be used for this. It would
> have syntax following its namesake in "console" kernel parameter, as
> described in Documentation/kernel-parameters.txt.
> 
> For example, the following settings in the .dts file would make UART5 to 
> be configured at 115200 baud, no parity, 8 bits.
> 
> serial at 2800 {           // PSC5
>          device_type = "serial";
>          compatible = "mpc5200b-psc-uart\0mpc5200-psc-uart";
>          port-number = <4>;  // Logical port assignment
>          options = "115200n8"
>          cell-index = <4>;
>          reg = <2800 100>;
>          interrupts = <2 c 0>;
>          interrupt-parent = <500>;
> };
> 
> 
> In case a console port has conflicting options given in the kernel 
> command line and in the DT blob, the command line values would be used.
> 
> Any comments on the above will be appreciated.

The device tree is intended to be an OS-independent description of the
state of the platform hardware as left by firmware (or bootwrapper).
It is not intended to contain kernel configuration parameters or options,
though there are a few exceptions.

So, this kind of change is unlikely to be accepted.

-Dale