[PATCH v2 0/2] irqchip/gic-v3: Enable non-coherent GIC designs probing
From: Lorenzo Pieralisi
Date: Wed Sep 06 2023 - 05:41:49 EST
This series is v2 of a previous version[1].
v1 -> v2:
- Updated DT bindings as per feedback
- Updated patch[2] to use GIC quirks infrastructure
[1] https://lore.kernel.org/all/20230905104721.52199-1-lpieralisi@xxxxxxxxxx
Original cover letter
---
The GICv3 architecture specifications provide a means for the
system programmer to set the shareability and cacheability
attributes the GIC components (redistributors and ITSes) use
to drive memory transactions.
Albeit the architecture give control over shareability/cacheability
memory transactions attributes (and barriers), it is allowed to
connect the GIC interconnect ports to non-coherent memory ports
on the interconnect, basically tying off shareability/cacheability
"wires" and de-facto making the redistributors and ITSes non-coherent
memory observers.
This series aims at starting a discussion over a possible solution
to this problem, by adding to the GIC device tree bindings the
standard dma-noncoherent property. The GIC driver uses the property
to force the redistributors and ITSes shareability attributes to
non-shareable, which consequently forces the driver to use CMOs
on GIC memory tables.
On ARM DT DMA is default non-coherent, so the GIC driver can't rely
on the generic DT dma-coherent/non-coherent property management layer
(of_dma_is_coherent()) which would default all GIC designs in the field
as non-coherent; it has to rely on ad-hoc dma-noncoherent property handling.
When a consistent approach is agreed upon for DT an equivalent binding will
be put forward for ACPI based systems.
Lorenzo Pieralisi (2):
dt-bindings: interrupt-controller: arm,gic-v3: Add dma-noncoherent
property
irqchip/gic-v3: Enable non-coherent redistributors/ITSes probing
.../interrupt-controller/arm,gic-v3.yaml | 12 +++++++++++
drivers/irqchip/irq-gic-common.h | 4 ++++
drivers/irqchip/irq-gic-v3-its.c | 21 +++++++++++++++----
drivers/irqchip/irq-gic-v3.c | 13 ++++++++++++
4 files changed, 46 insertions(+), 4 deletions(-)
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2.34.1