of_serial and device trees

[Simon Kagstrom]

Hi Scott!

Thanks a lot for all your help with the device tree! As you suspected,
I'm writing for a fairly old kernel (2.6.21, WindRiver). I know, I know.

On Tue, 24 Mar 2009 10:55:45 -0500
Scott Wood <scottwood at freescale.com> wrote:

> Add compatible = "simple-bus".  This lets children of this node be probed
> by of_platform drivers (make sure you list simple-bus when calling
> of_platform_bus_probe), and in a few other places (like legacy_serial.c).

Right, thanks. I've added this of_platform_bus_probe as an initcall,
and it now tries to configure the serial ports as expected (and with
some other issues).

> Compatible should be of the form "vendor,device" -- and does "isf"
> uniquely identify the specific FPGA logic, or are there other versions
> out there (or likely to exist in the future)?  Note that there are some
> bad examples in existing device trees that have yet to be fixed.

There are no other versions yet, but I suppose there will be (it's
implemented in a FPGA after all!). So what is the general handling of
versions, should it be something like

  compatible = "ericsson,isf-pic", "ericsson,isf-pic-v2"

etc if we'd make new revisions of the device?

> I'm guessing that your FPGA PIC driver isn't getting its register address
> from the device tree, given that it works without the ranges property?

It is, but I didn't check it for correctness yet, so I suppose I might
have mapped the wrong thing. The code looks like this:

        struct resource phys_addr;

        if (of_address_to_resource(np, 0, &phys_addr) != 0) {
                 printk(KERN_ERR": Could not get ISF PIC memory resource\n");
                 return NULL;
         }

	spin_lock_init(&isf->lock);
	isf->ioaddr = ioremap(phys_addr.start,
	                phys_addr.end - phys_addr.start);

So I should use the reg property and platform_get_resource() instead?

// Simon