Re: RFC: MPC52xx serial port configuration from DT blob

["Grant Likely" <grant.likely@secretlab.ca>]

On 13 Apr 2007 16:24:22 -0700, Dale Farnsworth <dale@farnsworth.org> wrote:
> 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@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.

Isn't the /chosen node intended for this kind of data?  Although I
must admit that I'm not at all familiar with the conventions used in
/chosen.

g.

-- 
Grant Likely, B.Sc. P.Eng.
Secret Lab Technologies Ltd.
grant.likely@secretlab.ca
(403) 399-0195