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Wed, 12 Aug 2026 13:43:08 -0700 (PDT) Received: from mietsbox ([2a00:808:140:f72e:ea47:3aff:fee8:3890]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5b4539ea237sm55308e87.18.2026.08.12.13.43.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 12 Aug 2026 13:43:05 -0700 (PDT) From: Guntis Belkovskis To: linux-i2c@vger.kernel.org Cc: guntis.belkovskis@gmail.com, Jean Delvare , Andi Shyti , linux-kernel@vger.kernel.org Subject: [PATCH] i2c: piix4: Add ACPI region conflict allowlist for Gigabyte X870 EAGLE WIFI7 Date: Wed, 12 Aug 2026 23:42:20 +0300 Message-ID: <20260812204220.74726-1-guntis.belkovskis@gmail.com> X-Mailer: git-send-email 2.55.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" On the Gigabyte X870 EAGLE WIFI7 motherboard, the ACPI DSDT declares the SMBus I/O ports (0x0B00 and 0x0B20) inside the _CRS method of \_SB.PCI0.S900 to report motherboard resource consumption. Inspection of the disassembled DSDT confirms that the firmware does not declare an OperationRegion over this range or execute any runtime AML methods against these ports. However, acpi_check_region() fails due to the static resource reservation, preventing i2c-piix4 from binding and blocking access to the DDR5 SPD and auxiliary controllers. Add a DMI allowlist entry for this motherboard so i2c-piix4 can safely bind and probe the SMBus. Verified working on physical hardware. Signed-off-by: Guntis Belkovskis --- drivers/i2c/busses/i2c-piix4.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-) diff --git a/drivers/i2c/busses/i2c-piix4.c b/drivers/i2c/busses/i2c-piix4.c index 7b6a4e201..33d4b0331 100644 --- a/drivers/i2c/busses/i2c-piix4.c +++ b/drivers/i2c/busses/i2c-piix4.c @@ -136,6 +136,18 @@ static const struct dmi_system_id piix4_dmi_ibm[] =3D { { } }; =20 +/* Allowlist for boards where ACPI reserves SMBus I/O in _CRS without acti= ve AML access */ +static const struct dmi_system_id piix4_dmi_acpi_allowlist[] =3D { + { + .ident =3D "GIGABYTE X870 EAGLE WIFI7", + .matches =3D { + DMI_MATCH(DMI_BOARD_VENDOR, "Gigabyte Technology Co., Ltd."), + DMI_MATCH(DMI_BOARD_NAME, "X870 EAGLE WIFI7"), + }, + }, + { } +}; + /* * SB800 globals */ @@ -403,8 +415,11 @@ static int piix4_setup_sb800(struct pci_dev *PIIX4_dev, if (retval) return retval; =20 - if (acpi_check_region(piix4_smba, SMBIOSIZE, piix4_driver.name)) - return -ENODEV; + if (acpi_check_region(piix4_smba, SMBIOSIZE, piix4_driver.name)) { + if (!dmi_check_system(piix4_dmi_acpi_allowlist)) { + return -ENODEV; + } + } =20 if (!request_region(piix4_smba, SMBIOSIZE, piix4_driver.name)) { dev_err(&PIIX4_dev->dev, "SMBus region 0x%x already in use!\n", --=20 2.55.0