gpu: nova-core: add the GIN interrupt tree and allocate its vectors

Servicing a GIN leaf has a required order: read its pending bits, then
clear them. Clearing a leaf first discards every vector latched in it,
and the hardware keeps no record of what was discarded. The interrupt
never arrives, and no register shows that it was ever pending.

Every subtree enabled at TOP also needs an allocated PCI vector with a
handler registered on it. Under MSI-X each subtree has its own table
entry. Linux masks every entry until a driver requests its IRQ, and a
masked entry sends no message. An enabled subtree whose entry was never
requested raises interrupts that never reach a handler, while the leaf
and TOP registers show them pending and enabled. Under MSI the whole
tree raises a single message, so one entry serves every subtree.

Add the CPU interrupt tree of one PCIe function. The tree allocates the
PCI vectors for the subtrees that it services and hands out the request
for each, so that the chipset is given once and the vectors live as
long as the tree. Reading a leaf yields the handle that clears it, so
that the wrong order does not compile. Building a tree fails if it
names a subtree that the GPU does not implement. A reset disables every
vector, clears every pending bit, rearms delivery, and leaves the
serviced subtrees disabled at TOP, so that a handler registered
afterwards receives no interrupt left over from boot.

Request MSI-X entries 0 through the highest serviced subtree, since an
MSI-X allocation cannot be sparse, and fall back to a single MSI
message, never to INTx.

[jhubbard: reworked on top of the GIN vector types: a leaf read yields
 the handle that clears it, enables are guarded, the leaf count and the
 rearm come from the interrupt HAL, the drain reads every implemented
 leaf rather than descending from TOP, the tree owns its PCI vectors,
 and a reset returns the tree to a known state before a handler is
 registered]

Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Will Pierce <wpierce@nvidia.com>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Link: https://patch.msgid.link/20260930034148.590687-7-jhubbard@nvidia.com
[acourbot: keep item that doesn't need to be exported private.]
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>

0 files changed, 0 insertions, 0 deletions