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

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Message-ID: <ZhQFICltEOcBHszS@lpieralisi>
Date: Mon, 8 Apr 2024 16:54:24 +0200
From: Lorenzo Pieralisi <lpieralisi@...nel.org>
To: linux-kernel@...r.kernel.org
Cc: 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 v5 0/1] irqchip/gic-v3: Enable non-coherent GIC designs
 probing

On Wed, Mar 06, 2024 at 03:43:32PM +0100, Lorenzo Pieralisi wrote:
> 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).

Hi,

just a reminder to ask how to proceed with this patch, I know it
is not urgent, just to understand how to handle it please.

The related ACPICA changes are already merged in the mainline.

Thanks,
Lorenzo

> 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
> >