linux-kernel - [PATCH v5 0/1] irqchip/gic-v3: Enable non-coherent GIC designs probing

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Date: Tue, 23 Jan 2024 12:03:31 +0100
From: Lorenzo Pieralisi <lpieralisi@...nel.org>
To: linux-kernel@...r.kernel.org
Cc: Lorenzo Pieralisi <lpieralisi@...nel.org>,
	linux-arm-kernel@...ts.infradead.org,
	linux-acpi@...r.kernel.org,
	acpica-devel@...ts.linux.dev,
	Mark Rutland <mark.rutland@....com>,
	Robin Murphy <robin.murphy@....com>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Fang Xiang <fangxiang3@...omi.com>,
	Marc Zyngier <maz@...nel.org>,
	Robert Moore <robert.moore@...el.com>
Subject: [PATCH v5 0/1] irqchip/gic-v3: Enable non-coherent GIC designs probing

This series is v5 of previous series:

v4: https://lore.kernel.org/all/20231227110038.55453-1-lpieralisi@kernel.org
v3: https://lore.kernel.org/all/20231006125929.48591-1-lpieralisi@kernel.org
v2: https://lore.kernel.org/all/20230906094139.16032-1-lpieralisi@kernel.org
v1: https://lore.kernel.org/all/20230905104721.52199-1-lpieralisi@kernel.org

v4 -> v5
	- ACPICA patches merged for v6.8
	- Refactored ACPI parsing code according to review
	- Rebased against v6.8-rc1

v3 -> v4:
	- Dropped patches [1-3], already merged
	- Added Linuxized ACPICA changes accepted upstream
	- Rebased against v6.7-rc3

v2 -> v3:
	- Added ACPICA temporary changes and ACPI changes to implement
	  ECR https://bugzilla.tianocore.org/show_bug.cgi?id=4557
	- ACPI changes are for testing purposes - subject to ECR code
	  first approval

v1 -> v2:
	- Updated DT bindings as per feedback
	- Updated patch[2] to use GIC quirks infrastructure

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 (1):
  irqchip/gic-v3: Enable non-coherent redistributors/ITSes ACPI probing

 drivers/acpi/processor_core.c    | 15 +++++++++++++++
 drivers/irqchip/irq-gic-v3-its.c |  4 ++++
 drivers/irqchip/irq-gic-v3.c     |  9 +++++++++
 include/linux/acpi.h             |  3 +++
 4 files changed, 31 insertions(+)

-- 
2.34.1