On Monday 07 January 2013, Vineet Gupta wrote:

On Wednesday 07 November 2012 07:46 PM, Arnd Bergmann wrote:

quoted

On Wednesday 07 November 2012, Vineet Gupta wrote:

(1) Although I don't need the container "fpga" I'm forced to - because
of_platform_populate( ) -> of_match_node( ) expects the @match arg to be NOT NULL.
So we pass of_default_bus_match_table and have the compat string "simple-bus" in
the container. Per [1] it seemed it was possible to add the serial device directly
w/o the container.

You could in theory make the serial port device itself be compatible to 
somthing that is being probed by of_platform_populate, but putting it
under a bus is the preferred way. Usually each system has at least one
bus that devices are connected to and I would recommend to represent all
buses in the device tree like they are in hardware.
 

(2) I need the following OF_DEV_AUXDATA to be able to "name" the device correctly
so that the registered driver [4] can bind with device. How do I match the driver
and devicetree node w/o this glue - it seems compatible="<manuf>,<model>" is not
enough. This also requires the uart base address to be specified (otherwise
of_dev_lookup() fails to identify the auxdata) which IMHO defeats the purpose of
devicetree in first place.
b
static struct of_dev_auxdata arcuart_auxdata_lookup[] __initdata = {
	OF_DEV_AUXDATA("snps,arc-uart", UART0_BASE, "arc-uart", arc_uart_info),
	{}
};

It should be enough to fill the drv->of_match_table member of the
platform_driver with the match table.

(3) After above, driver's probe routine is getting called with platform_device->id
= -1 and it seems of_device_add() is doing that purposely. How do I handle that.

What do you need the id for?

(4) Is above standalone "interrupts" string OK, or do I have to explicitly
instantiate the in-core intc as well. Since it is integral part of cpu, I really
don't need any support code to explicitly instantiate it. Also it is not accessed
via mem map - but special ARC instructions in aux address space of cpu.

Interrupts are a little tricky. You need to create a bindind for your interrupt
controller first and make the irqchip driver use irq domains in order for the
irq description in the device tree to be mapped into a linux-internal irq number.

In the simple case where you only have one irqchip in the system, you can use
a "legacy" irq domain that simply translates the numbers 1:1. In some cases,
it does make sense though (even with the legacy domain) to include additional
flags in the device tree irq descriptor, e.g. the irq polarity and
edge/level/message indication. Please read up on these and ask again if you have
more questions.

	Arnd