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Date: Wed, 6 Mar 2024 15:43:32 +0100
From: Lorenzo Pieralisi <lpieralisi@kernel.org>
To: linux-kernel@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org, linux-acpi@vger.kernel.org,
	acpica-devel@lists.linux.dev, Mark Rutland <mark.rutland@arm.com>,
	Robin Murphy <robin.murphy@arm.com>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Fang Xiang <fangxiang3@xiaomi.com>, Marc Zyngier <maz@kernel.org>,
	Robert Moore <robert.moore@intel.com>
Subject: Re: [PATCH v5 0/1] irqchip/gic-v3: Enable non-coherent GIC designs
 probing
Message-ID: <ZeiBFBDhwlJnCUZ2@lpieralisi>
References: <20240123110332.112797-1-lpieralisi@kernel.org>
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In-Reply-To: <20240123110332.112797-1-lpieralisi@kernel.org>

On Tue, Jan 23, 2024 at 12:03:31PM +0100, Lorenzo Pieralisi wrote:
> 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

Hi Marc, all,

this is not an urgent fix (I don't think there is any ACPI platform
affected in the field so it is not even a fix), I am just asking please
what should I do with it, I appreciate it is late in the cycle (and I
know some fixes got merged in -rcX leading up to -rc7 that are
pre-requisite for this patch to work).

Thanks,
Lorenzo

> 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
>