On Mon, 10 Mar 2025 at 06:29, Sourojeet Adhikari
<s23ad...@csclub.uwaterloo.ca> wrote:
>
> Hello,
>
> So far I've figured out that I need to add a member called SplitIRQ
> in the BCMSocPeripheralBaseState struct, which is of size defined
> by `BCM2835_NUM_SPLITTERS`. Then from what I can tell through
> reading through the codebase, I should do something similar to
> what happens in `exynos4210.c` in the `exynos4210_init_board_irqs`
> function?
QEMU qdev devices have a multiple-stage initialization process:
(1) 'init', which in this case means calling object_initialize_child().
In this case you should do this in raspi_peripherals_base_init(),
where we do this for the other child devices of the common
peripheral base object.
(2) set properties (in this case the "num-lines" property, which
needs to be set to 2). You do this in the parent object's 'realize'
method, in this case bcm_soc_peripherals_common_realize().
There are several different equivalent APIs to set a simple
integer property; using qdev_prop_set_uint16() like the exynos
code does is fine.
(3) realize the device by calling qdev_realize(); this has to be
done after all properties are set.
(4) wire up the input and output GPIO lines (you want to wire up
a GPIO only once the devices on both ends have been realized).
For this case, in the bcm_soc_peripherals_common_realize()
function we're going to wire up the the device's outbound
IRQ to the input of the appropriate splitter, and connect
output 0 of that splitter to the BCM2835_IC correct interrupt
controller input.
(5) The last bit of wiring, where we connect splitter output 1 to
the correct GIC input, we do in bcm2838.c, and only after
we've called 'realize' for both the bcm2835_peripherals object
and the GIC object.
> Sorry for taking a while to get back and still having quite a few
> questions about this. Thank you for helping me out with writting
> this patch.
No worries; this stuff is all quite complicated and we don't
really document it very well.
thanks
-- PMM
