On 05/09/2023 11:47 am, Lorenzo Pieralisi wrote:
The GIC v3 specifications allow redistributors and ITSes interconnect
ports used to access memory to be wired up in a way that makes the
respective initiators/memory observers non-coherent.
Add the standard dma-noncoherent property to the GICv3 bindings to
allow firmware to describe the redistributors/ITSes components and
interconnect ports behaviour in system designs where the redistributors
and ITSes are not coherent with the CPU.
Signed-off-by: Lorenzo Pieralisi <lpieralisi@xxxxxxxxxx>
Cc: Rob Herring <robh@xxxxxxxxxx>
---
.../bindings/interrupt-controller/arm,gic-v3.yaml | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/Documentation/devicetree/bindings/interrupt-controller/arm,gic-v3.yaml b/Documentation/devicetree/bindings/interrupt-controller/arm,gic-v3.yaml
index 39e64c7f6360..0a81ae4519a6 100644
--- a/Documentation/devicetree/bindings/interrupt-controller/arm,gic-v3.yaml
+++ b/Documentation/devicetree/bindings/interrupt-controller/arm,gic-v3.yaml
@@ -106,6 +106,10 @@ properties:
$ref: /schemas/types.yaml#/definitions/uint32
maximum: 4096
+ dma-noncoherent:
+ description: |
+ Present if the GIC redistributors are not cache coherent with the CPU.
I wonder if it's worth being a bit more specific here, e.g. "if the GIC
{redistributors,ITS} permit programming cacheable inner-shareable memory
attributes, but are connected to a non-coherent downstream
interconnect." That might help clarify why the negative property, which
could seem a bit backwards at first glance, and that it's not so
important in the cases where the GIC itself is fundamentally
non-coherent anyway (which *is* software-discoverable).
Otherwise, this is the same approach that I like and have previously
lobbied for, so obviously I approve :)
(plus I do think it's the right shape to be able to slot an equivalent
field into ACPI MADT entries without *too* much bother)
Thanks,
Robin.
+
msi-controller:
description:
Only present if the Message Based Interrupt functionality is
@@ -193,6 +197,10 @@ patternProperties:
compatible:
const: arm,gic-v3-its
+ dma-noncoherent:
+ description: |
+ Present if the GIC ITS is not cache coherent with the CPU.
+
msi-controller: true
"#msi-cells":
