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Many DSDTs for Kaby Lake and Kaby Lake Refresh models contain a _SB.PCI0.GEXP ACPI Device node describing an I2C attached PCA953x GPIO expander. This seems to be something which is copy and pasted from the DSDT from some reference design since this ACPI Device is present even on models where no such GPIO expander is used at all, such as on the Microsoft Surface Go & Go 2. This ACPI Device is a problem because it contains a SystemMemory OperationRegion which covers the MMIO for the I2C4 I2C controller. This causes the MFD cell for the I2C4 controller to not be instantiated due to a resource conflict, requiring the use of acpi_enforce_resources=lax to work around this. I have done an extensive analysis of all the ACPI tables on the Microsoft Surface Go and the _SB.PCI0.GEXP ACPI Device's methods are not used by any code in the ACPI tables, neither are any of them directly called by any Linux kernel code. This is unsurprising since running i2cdetect on the I2C4 bus shows that there is no GPIO expander chip present on these devices at all. This commit adds a PCI subsystem vendor:device table listing PCI devices where it is known to be safe to ignore resource conflicts with ACPI declared SystemMemory regions. This makes the I2C4 bus work out of the box on the Microsoft Surface Go & Go 2, which is necessary for the cameras on these devices to work. Signed-off-by: Hans de Goede <hdegoede@redhat.com> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com> Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com> Signed-off-by: Lee Jones <lee.jones@linaro.org> Link: https://lore.kernel.org/r/20211203115108.89661-1-hdegoede@redhat.com |
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| certs | ||
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| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.