[U-Boot] serial : Device tree support for multiple serial devices.

[Simon Glass]

Hi,

On Mon, Jan 23, 2012 at 1:01 PM, hanumant <hanumant07 at gmail.com> wrote:
> Hi
>
>        The board that I am working on has multiple serial ports.
> I am trying to use device trees to configure board resource of these ports
> as well as the serial framework. So the driver doesnot know apriori the
> number of uart ports on the board. But querries the device tree for it.I am
> facing the following issues.
>
> 1) Ports are memory mapped and each port has its own register space.
> As such the serial framework apis dont provide for passing a port id at the
> time of the call. So how do i access the correct register space for the
> corresponding port?. Or should i define for my own set of apis to be called
> by clients, allowing me to access specific ports corresponding address
> space, and use the serial framework api's only for the default serial
> console?
>
> 2) the default serial console, also gets configured based on information
> obtained from the device tree, at run time. If i keep a global
> representation of the default serial console with its base address etc, it
> will still have to be reinitialized after relocation. The
> default_serial_console() gives me an opportunity to reinitialize the global
> structure. Is that the way to go?

I have done similar things. IMO the right way to go is to refactor the
serial API so that it takes a device pointer as the first parameter. I
haven't done it though.

What I did for now was to implement a new fdt_serial.c file which
defines 4 separate sets of function (each set containing putc, getc,
etc.) with the device pointer built in to those functions. It's really
ugly, and is what eserial does. Those functions look up the device
tree during init and redirect to the real serial driver's functions of
the same name.

I could probably rustle up a patch if it would help.

Regards,
Simon

>
> Thanks
> Hanumant
>
>
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