From 0be8153cbc2af9a96e9ab8631fc3ba23bb52dbe3 Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Tue, 8 May 2018 13:14:30 +0100 Subject: genirq/msi: Allow level-triggered MSIs to be exposed by MSI providers So far, MSIs have been used to signal edge-triggered interrupts, as a write is a good model for an edge (you can't "unwrite" something). On the other hand, routing zillions of wires in an SoC because you need level interrupts is a bit extreme. People have come up with a variety of schemes to support this, which involves sending two messages: one to signal the interrupt, and one to clear it. Since the kernel cannot represent this, we've ended up with side-band mechanisms that are pretty awful. Instead, let's acknoledge the requirement, and ensure that, under the right circumstances, the irq_compose_msg and irq_write_msg can take as a parameter an array of two messages instead of a pointer to a single one. We also add some checking that the compose method only clobbers the second message if the MSI domain has been created with the MSI_FLAG_LEVEL_CAPABLE flags. Signed-off-by: Marc Zyngier Signed-off-by: Thomas Gleixner Cc: Rob Herring Cc: Jason Cooper Cc: Ard Biesheuvel Cc: Srinivas Kandagatla Cc: Thomas Petazzoni Cc: Miquel Raynal Link: https://lkml.kernel.org/r/20180508121438.11301-2-marc.zyngier@arm.com --- include/linux/msi.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux/msi.h') diff --git a/include/linux/msi.h b/include/linux/msi.h index 1f1bbb5b4679..5839d8062dfc 100644 --- a/include/linux/msi.h +++ b/include/linux/msi.h @@ -289,6 +289,8 @@ enum { * MSI_FLAG_ACTIVATE_EARLY has been set. */ MSI_FLAG_MUST_REACTIVATE = (1 << 5), + /* Is level-triggered capable, using two messages */ + MSI_FLAG_LEVEL_CAPABLE = (1 << 6), }; int msi_domain_set_affinity(struct irq_data *data, const struct cpumask *mask, -- cgit v1.2.3