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author | 2018-05-08 13:14:30 +0100 | |
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committer | 2018-05-13 15:58:59 +0200 | |
commit | 0be8153cbc2af9a96e9ab8631fc3ba23bb52dbe3 (patch) | |
tree | 84328dcb38f9a9d81ce2086419fe40d7b24909dc /include/linux/msi.h | |
parent | genirq/irq_sim: Use the SPDX license identifier in the header (diff) | |
download | linux-0be8153cbc2af9a96e9ab8631fc3ba23bb52dbe3.tar.gz linux-0be8153cbc2af9a96e9ab8631fc3ba23bb52dbe3.tar.bz2 linux-0be8153cbc2af9a96e9ab8631fc3ba23bb52dbe3.zip |
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 <marc.zyngier@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Rob Herring <robh@kernel.org>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Cc: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lkml.kernel.org/r/20180508121438.11301-2-marc.zyngier@arm.com
Diffstat (limited to 'include/linux/msi.h')
-rw-r--r-- | include/linux/msi.h | 2 |
1 files changed, 2 insertions, 0 deletions
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, |