linux-kernel - Re: [PATCH v4 0/3] irqchip/gic-v3: Enable non-coherent GIC designs probing

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Date: Wed, 3 Jan 2024 14:43:16 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Lorenzo Pieralisi <lpieralisi@...nel.org>
Cc: linux-kernel@...r.kernel.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: Re: [PATCH v4 0/3] irqchip/gic-v3: Enable non-coherent GIC designs probing

On Wed, Dec 27, 2023 at 12:00 PM Lorenzo Pieralisi
<lpieralisi@...nel.org> wrote:
>
> This series is v4 of previous series:
>
> 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
>
> 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 (3):
>   ACPICA: MADT: Add GICC online capable bit handling
>   ACPICA: MADT: Add new MADT GICC/GICR/ITS non-coherent flags handling
>   irqchip/gic-v3: Enable non-coherent redistributors/ITSes ACPI probing
>
>  drivers/acpi/processor_core.c    | 21 +++++++++++++++++++++
>  drivers/irqchip/irq-gic-common.h |  8 ++++++++
>  drivers/irqchip/irq-gic-v3-its.c |  4 ++++
>  drivers/irqchip/irq-gic-v3.c     |  9 +++++++++
>  include/acpi/actbl2.h            | 12 ++++++++++--
>  include/linux/acpi.h             |  3 +++
>  6 files changed, 55 insertions(+), 2 deletions(-)
>
> --

I can apply the first 2 patches, but I would need an ACK for the 3rd one.

Alternatively, feel free to add

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

to the first 2 patches and route them via ARM64.

Thanks!