[PATCH] PCI: rcar-host: Use proper IRQ domain

[Claudiu <claudiu.beznea@xxxxxxxxx>]

From: Claudiu Beznea <claudiu.beznea.uj@xxxxxxxxxxxxxx>

Starting with commit dd26c1a23fd5 ("PCI: rcar-host: Switch to
msi_create_parent_irq_domain()"), the MSI parent IRQ domain is NULL because
the object of type struct irq_domain_info passed to:

msi_create_parent_irq_domain() ->
  irq_domain_instantiate()() ->
    __irq_domain_instantiate()

has no reference to the parent IRQ domain. Using msi->domain->parent as an
argument for generic_handle_domain_irq() leads to a "Unable to handle
kernel NULL pointer dereference at virtual address" error.

This error was identified while switching the upcoming RZ/G3S PCIe host
controller driver to msi_create_parent_irq_domain() (which was using a
similar pattern to handle MSIs (see link section)), but it was not tested
on hardware using the pcie-rcar-host controller driver due to lack of
hardware.

Link: https://lore.kernel.org/all/20250704161410.3931884-6-claudiu.beznea.uj@xxxxxxxxxxxxxx/
Fixes: dd26c1a23fd5 ("PCI: rcar-host: Switch to msi_create_parent_irq_domain()")
Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@xxxxxxxxxxxxxx>
---
 drivers/pci/controller/pcie-rcar-host.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pci/controller/pcie-rcar-host.c b/drivers/pci/controller/pcie-rcar-host.c
index fe288fd770c4..4780e0109e58 100644
--- a/drivers/pci/controller/pcie-rcar-host.c
+++ b/drivers/pci/controller/pcie-rcar-host.c
@@ -584,7 +584,7 @@ static irqreturn_t rcar_pcie_msi_irq(int irq, void *data)
 		unsigned int index = find_first_bit(&reg, 32);
 		int ret;
 
-		ret = generic_handle_domain_irq(msi->domain->parent, index);
+		ret = generic_handle_domain_irq(msi->domain, index);
 		if (ret) {
 			/* Unknown MSI, just clear it */
 			dev_dbg(dev, "unexpected MSI\n");
-- 
2.43.0