[PATCH v2 05/14] genirq/msi: Provide DOMAIN_BUS_MSI_REMAP

[Andrew Jones]

Add a bus token for MSI domains that remap interrupts, needed by the
upcoming RISC-V IOMMU interrupt-remapping domain to distinguish itself
from NEXUS domains. The token is generic because remapping itself is
the only property that needs to be conveyed -- there is nothing
RISC-V-specific about it.

Such a domain implements init_dev_msi_info() via
msi_parent_init_dev_msi_info(), which leaves 'domain' pointing at the
NEXUS domain while 'real_parent' points at the remap domain itself.
Accept that combination in msi_lib_init_dev_msi_info(); no other
msi-lib changes are needed.

Signed-off-by: Andrew Jones <andrew.jones@xxxxxxxxxxxxxxxx>
Reviewed-by: Nutty Liu <nutty.liu@xxxxxxxxxxx>
---
 drivers/irqchip/irq-msi-lib.c  | 8 ++++----
 include/linux/irqdomain_defs.h | 1 +
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/irqchip/irq-msi-lib.c b/drivers/irqchip/irq-msi-lib.c
index 45e0ed3134ce..9027dfbab15e 100644
--- a/drivers/irqchip/irq-msi-lib.c
+++ b/drivers/irqchip/irq-msi-lib.c
@@ -36,14 +36,14 @@ bool msi_lib_init_dev_msi_info(struct device *dev, struct irq_domain *domain,
 		return false;
 
 	/*
-	 * MSI parent domain specific settings. For now there is only the
-	 * root parent domain, e.g. NEXUS, acting as a MSI parent, but it is
-	 * possible to stack MSI parents. See x86 vector -> irq remapping
+	 * MSI parent domain specific settings. There may be only the root
+	 * parent domain, e.g. NEXUS, acting as a MSI parent, or there may
+	 * be stacked MSI parents, typically used for remapping.
 	 */
 	if (domain->bus_token == pops->bus_select_token) {
 		if (WARN_ON_ONCE(domain != real_parent))
 			return false;
-	} else {
+	} else if (real_parent->bus_token != DOMAIN_BUS_MSI_REMAP) {
 		WARN_ON_ONCE(1);
 		return false;
 	}
diff --git a/include/linux/irqdomain_defs.h b/include/linux/irqdomain_defs.h
index 3a03bdfeeee9..954cf585b3c4 100644
--- a/include/linux/irqdomain_defs.h
+++ b/include/linux/irqdomain_defs.h
@@ -26,6 +26,7 @@ enum irq_domain_bus_token {
 	DOMAIN_BUS_AMDVI,
 	DOMAIN_BUS_DEVICE_MSI,
 	DOMAIN_BUS_WIRED_TO_MSI,
+	DOMAIN_BUS_MSI_REMAP,
 };
 
 #endif /* _LINUX_IRQDOMAIN_DEFS_H */
-- 
2.43.0