[PATCH v2 2/9] genirq/msi: Limit level-triggered MSI to platform devices

[Marc Zyngier]

Nobody would be insane enough to try and use level triggered
MSIs on PCI, but let's make sure it doesn't happen. Also,
let's mandate that the irqchip backing the platform MSI domain
is providing the IRQCHIP_SUPPORTS_LEVEL_MSI flag.

Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
---
 drivers/base/platform-msi.c     | 3 +++
 drivers/bus/fsl-mc/fsl-mc-msi.c | 2 ++
 drivers/pci/msi.c               | 3 +++
 include/linux/irq.h             | 1 +
 4 files changed, 9 insertions(+)

diff --git a/drivers/base/platform-msi.c b/drivers/base/platform-msi.c
index 8e22073aeeed..60d6cc618f1c 100644
--- a/drivers/base/platform-msi.c
+++ b/drivers/base/platform-msi.c
@@ -101,6 +101,9 @@ static void platform_msi_update_chip_ops(struct msi_domain_info *info)
 		chip->irq_set_affinity = msi_domain_set_affinity;
 	if (!chip->irq_write_msi_msg)
 		chip->irq_write_msi_msg = platform_msi_write_msg;
+	if (WARN_ON((info->flags & MSI_FLAG_LEVEL_CAPABLE) &&
+		    !(chip->flags & IRQCHIP_SUPPORTS_LEVEL_MSI)))
+		info->flags &= ~MSI_FLAG_LEVEL_CAPABLE;
 }
 
 static void platform_msi_free_descs(struct device *dev, int base, int nvec)
diff --git a/drivers/bus/fsl-mc/fsl-mc-msi.c b/drivers/bus/fsl-mc/fsl-mc-msi.c
index ec35e255b496..8b9c66d7c4ff 100644
--- a/drivers/bus/fsl-mc/fsl-mc-msi.c
+++ b/drivers/bus/fsl-mc/fsl-mc-msi.c
@@ -163,6 +163,8 @@ struct irq_domain *fsl_mc_msi_create_irq_domain(struct fwnode_handle *fwnode,
 {
 	struct irq_domain *domain;
 
+	if (WARN_ON((info->flags & MSI_FLAG_LEVEL_CAPABLE)))
+		info->flags &= ~MSI_FLAG_LEVEL_CAPABLE;
 	if (info->flags & MSI_FLAG_USE_DEF_DOM_OPS)
 		fsl_mc_msi_update_dom_ops(info);
 	if (info->flags & MSI_FLAG_USE_DEF_CHIP_OPS)
diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index 30250631efe7..f45b74fcc059 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -1434,6 +1434,9 @@ struct irq_domain *pci_msi_create_irq_domain(struct fwnode_handle *fwnode,
 {
 	struct irq_domain *domain;
 
+	if (WARN_ON(info->flags & MSI_FLAG_LEVEL_CAPABLE))
+		info->flags &= ~MSI_FLAG_LEVEL_CAPABLE;
+
 	if (info->flags & MSI_FLAG_USE_DEF_DOM_OPS)
 		pci_msi_domain_update_dom_ops(info);
 	if (info->flags & MSI_FLAG_USE_DEF_CHIP_OPS)
diff --git a/include/linux/irq.h b/include/linux/irq.h
index 65916a305f3d..b2067083aa94 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -512,6 +512,7 @@ enum {
 	IRQCHIP_SKIP_SET_WAKE		= (1 <<  4),
 	IRQCHIP_ONESHOT_SAFE		= (1 <<  5),
 	IRQCHIP_EOI_THREADED		= (1 <<  6),
+	IRQCHIP_SUPPORTS_LEVEL_MSI	= (1 <<  7),
 };
 
 #include <linux/irqdesc.h>
-- 
2.14.2