Re: [PATCH v4] irqchip/gic-v3: Add Altera SoCFPGA Agilex5 GIC600 DMA32 erratum workaround

[Marc Zyngier <maz@kernel.org>]

On Fri, 04 Sep 2026 10:11:14 +0100,
Adrian Ng Ho Yin <adrian.ho.yin.ng@altera.com> wrote:
> 
> Agilex5 integrates GIC600 with an ACE-lite interface limited to a 32-bit
> address bus, so the ITS can only access the first 4 GB of physical address
> space. Add ALTERA_ERRATUM_AGILEX5 and register intel,socfpga-agilex5 on the
> existing dma_32bit_impaired_platforms list.
> 
> This limitation is documented as Agilex 5 ES Device Errata 2.1.23 (825514).
> 
> Signed-off-by: Adrian Ng Ho Yin <adrian.ho.yin.ng@altera.com>
> ---
> Link: https://docs.altera.com/r/docs/825514/current/agilex-5-es-device-errata-and-user-guidelines/hps-gicv3-its-and-lpi-unable-to-access-physical-memory-larger-than-32-bits-causing-msi-x-interrupt-failure
> Link: https://lore.kernel.org/linux-arm-kernel/372f059069a5551ea1096015f855cc306dbd7cd4.1747368554.git.adrianhoyin.ng@altera.com/ # v1
> Link: https://lore.kernel.org/linux-arm-kernel/6a44509ca0edaabc17e59d2e27fef1c782183456.1751618484.git.adrianhoyin.ng@altera.com/ # v2
> Link: https://lore.kernel.org/linux-arm-kernel/20260622024945.21354-1-muhammad.nazim.amirul.nazle.asmade@altera.com/ # v3 (untagged)
> 
> Changes in v4:
> - Rebase onto dma_32bit_impaired_platforms shared quirk (post Renesas)
> - Add ALTERA_ERRATUM_AGILEX5 Kconfig and silicon-errata entry
> - Cite Agilex 5 ES Device Errata 2.1.23
> 
> Changes in v3:
> - Extend existing Rockchip dma32 quirk path for Agilex5
> 
> Changes in v2:
> - Drop DT binding quirk; use IIDR + of_machine_is_compatible()
> 
>  Documentation/arch/arm64/silicon-errata.rst |  3 +++
>  arch/arm64/Kconfig                          | 10 ++++++++++
>  drivers/irqchip/irq-gic-v3-its.c            |  3 +++
>  3 files changed, 16 insertions(+)
> 
> diff --git a/Documentation/arch/arm64/silicon-errata.rst b/Documentation/arch/arm64/silicon-errata.rst
> index ac3248b9f2f3..8522ba072040 100644
> --- a/Documentation/arch/arm64/silicon-errata.rst
> +++ b/Documentation/arch/arm64/silicon-errata.rst
> @@ -53,6 +53,9 @@ stable kernels.
>  | Allwinner      | A64/R18         | UNKNOWN1        | SUN50I_ERRATUM_UNKNOWN1     |
>  +----------------+-----------------+-----------------+-----------------------------+
>  +----------------+-----------------+-----------------+-----------------------------+
> +| Altera         | SoCFPGA Agilex5 | 2.1.23          | ALTERA_ERRATUM_AGILEX5      |
> ++----------------+-----------------+-----------------+-----------------------------+
> ++----------------+-----------------+-----------------+-----------------------------+
>  | Ampere         | AmpereOne       | AC03_CPU_38     | AMPERE_ERRATUM_AC03_CPU_38  |
>  +----------------+-----------------+-----------------+-----------------------------+
>  | Ampere         | AmpereOne       | AC03_CPU_57     | N/A                         |
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index b5a51b0ef944..e3afb591db68 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -418,6 +418,16 @@ menu "Kernel Features"
>  
>  menu "ARM errata workarounds via the alternatives framework"
>  
> +config ALTERA_ERRATUM_AGILEX5

Is this the sole erratum on this HW? The documentation says
otherwise. So please add a suffix that uniquely identifies it
(something like ALTERA_ERRATUM_AGILEX5_2_1_23).

> +	bool "Altera Agilex5: GIC600 can not access physical addresses higher than 4GB"
> +	default y
> +	help
> +	  The Altera SoCFPGA Agilex5 GIC600 SoC integration has ACE-lite
> +	  addressing limited to the first 32bit of physical address space.
> +	  This is documented as Agilex 5 ES Device Errata 2.1.23 (825514).
> +
> +	  If unsure, say Y.
> +

This is in the wrong place. Look where the other GIC errata are, and
put it there. Also, this should be selected by ARCH_INTEL_SOCFPGA,
instead of being left for the user to choose.

	M.

-- 
Jazz isn't dead. It just smells funny.