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

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

+	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.
+