So far, it has been assumed that only level 2 interrupts can be shared
via the `CONFIG_SHARED_INTERRUPTS` option, but this is not true. In the
case of i.MX95, for instance, level 1 interrupt 143 is shared among EDMA
channels 30 and 31.
Due to the previous assumption, the irqsteer driver currently performs
reference counting for all level 2 interrupts aggregated by each
dispatcher and, of course, for the level 1 interrupts the dispatchers are
attached to. For instance, assuming a machine with 100 level 1 interrupts
and 1 irqsteer dispatcher attached to line 50 this would mean reference
counting is performed solely for line 50 (and the level 2 interrupts MUX'd
into this line).
Going back to i.MX95, since there's no dispatcher attached to IRQ line 143
that means there's no reference counting for it. In turn, this means that
the IRQ line can be disabled accidentally on a channel release() operation
while the other channel is active.
To protect against such cases, refactor the level1 interrupt reference
counting. Now, reference counting is performed for _all_ level 1
interrupts.
Additionally, simplify the locking logic. Ideally, there would be a lock
for each dispatcher protecting the level 2 interrupts and 1 global lock
protecting the level 1 interrupts. Instead of this approach (which is a
bit more complex), simply use a global lock for all interrupts. If finer
granularity is required then it can be added later on.
Signed-off-by: Laurentiu Mihalcea <laurentiu.mihalcea@nxp.com>
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