irqchip: crossbar: introduce ti,irqs-skip to skip

When, in the system due to varied reasons, interrupts might be unusable
due to hardware behavior, but register maps do exist, then those interrupts
should be skipped while mapping irq to crossbars.

Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Sricharan R <r.sricharan@ti.com>
irqchip: crossbar: initialise the crossbar with a safe value

Since crossbar is s/w configurable, the initial settings of the
crossbar cannot be assumed to be sane. This implies that:
a) On initialization all un-reserved crossbars must be initialized to
   a known 'safe' value.
b) When unmapping the interrupt, the safe value must be written to
   ensure that the crossbar mapping matches with interrupt controller
   usage.

So provide a safe value in the dt data to map if
'0' is not safe for the platform and use it during init and unmap

While at this, fix the below checkpatch warning.
Fixes checkpatch warning:
WARNING: Unnecessary space before function pointer arguments
 #37: FILE: drivers/irqchip/irq-crossbar.c:37:
 +	void (*write) (int, int);

Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Sricharan R <r.sricharan@ti.com>
irqchip: crossbar: change allocation logic by reversing search for free irqs

Reverse the search algorithm to ensure that address mapping and IRQ
allocation logics are proper. This makes the below bugs visible sooner.

class 1. address space errors -> example:
reg = <a size_b>
ti,max-irqs =  is a wrong parameter

class 2: irq-reserved list - which decides which entries in the
address space is not actually wired in

class 3: wrong list of routable-irqs.

In general allocating from max to min tends to have benefits in
ensuring the different issues that may be present in dts is easily
caught at definition time, rather than at a later point in time.

Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Sricharan R <r.sricharan@ti.com>
irqchip: crossbar: remove IS_ERR_VALUE check

IS_ERR_VALUE makes sense only *if* there could be valid values in
negative error range. But in the cases that we do use it, there is no
such case. Just remove the same.

Signed-off-by: Nishanth Menon <nm@ti.com>
irqchip: crossbar: fix sparse and checkpatch warnings

There is absolutely no need for crossbar driver to expose functions and
variables into global namespace. So make them all static

Also fix a couple of checkpatch warnings.

Fixes sparse warnings:
drivers/irqchip/irq-crossbar.c:129:29: warning: symbol 'routable_irq_domain_ops' was not declared. Should it be static?
drivers/irqchip/irq-crossbar.c:261:12: warning: symbol 'irqcrossbar_init' was not declared. Should it be static?

Checkpatch warnings:
WARNING: Prefer kcalloc over kzalloc with multiply
+	cb->irq_map = kzalloc(max * sizeof(int), GFP_KERNEL);

WARNING: Prefer kcalloc over kzalloc with multiply
+	cb->register_offsets = kzalloc(max * sizeof(int), GFP_KERNEL);

Signed-off-by: Nishanth Menon <nm@ti.com>
irqchip: crossbar: fix kerneldoc warning

Adding missing properties for kerneldoc (@write) and cleanup
of harmless warnings while we are here.

kerneldoc warnings:
Warning(drivers/irqchip/irq-crossbar.c:27): missing initial short description on line:
 * struct crossbar_device: crossbar device description
Info(drivers/irqchip/irq-crossbar.c:27): Scanning doc for struct
Warning(drivers/irqchip/irq-crossbar.c:39): No description found for parameter 'write'
2 warnings

Signed-off-by: Nishanth Menon <nm@ti.com>
irqchip: crossbar: return proper error value

crossbar_of_init always returns -ENOMEM in case of errors.
There can be other causes of failure like invalid data from
DT. So return a appropriate error value for that case.

Signed-off-by: Nishanth Menon <nm@ti.com>
irqchip: crossbar: change the goto naming

Using err1,2,3,4 etc makes it hard to ensure a new exit path in the
middle will not result in spurious changes, so rename the error paths
as per the function it does.

Signed-off-by: Nishanth Menon <nm@ti.com>
irqchip: crossbar: set cb pointer to null in case of error

If crossbar_of_init returns with a error, then set the cb pointer
to null.

Signed-off-by: Sricharan R <r.sricharan@ti.com>
irqchip: crossbar: add kerneldoc for crossbar_domain_unmap callback

Adding kerneldoc for unmap callback function.

Signed-off-by: Sricharan R <r.sricharan@ti.com>
irqchip: crossbar: introduce ti,max-crossbar-sources to identify valid crossbar mapping

Currently we attempt to map any crossbar value to an IRQ, however,
this is not correct from hardware perspective. There is a max crossbar
event number upto which hardware supports. So describe the same in
device tree using 'ti,max-crossbar-sources' property and use it to
validate requests.

Signed-off-by: Nishanth Menon <nm@ti.com>
irqchip: crossbar: introduce centralized check for crossbar write

This is a basic check to ensure that crossbar register needs to be
written. This ensures that we have a common check which is used in
both map and unmap logic.

Signed-off-by: Nishanth Menon <nm@ti.com>
documentation: dt: omap: crossbar: add description for interrupt consumer

The current crossbar description does not include the description
required for the consumer of the crossbar, a.k.a devices whoes events
pass through the crossbar into the GIC interrupt controller.

So, provide documentation for the same.

Signed-off-by: Nishanth Menon <nm@ti.com>
irqchip: crossbar allow for quirky hardware with direct hardwiring of GIC

On certain platforms such as DRA7, SPIs 0, 1, 2, 3, 5, 6, 10, 131,
132, 133 are direct wired to hardware blocks bypassing crossbar.
This quirky implementation is *NOT* supposed to be the expectation
of crossbar hardware usage. However, these are already marked in our
description of the hardware with SKIP and RESERVED where appropriate.

Unfortunately, we need to be able to refer to these hardwired IRQs.
So, to request these, crossbar driver can use the existing information
from it's table that these SKIP/RESERVED maps are direct wired sources
and generic allocation/programming of crossbar should be avoided.

Signed-off-by: Nishanth Menon <nm@ti.com>