9d9bcae47f
The clk and regulator frameworks expect clk/regulator consumer-devices to have info about the consumed clks/regulators described in the device's fw_node. To work around cases where this info is not present in the firmware tables, which is often the case on x86/ACPI devices, both frameworks allow the provider-driver to attach info about consumers to the clks/regulators when registering these. This causes problems with the probe ordering wrt drivers for consumers of these clks/regulators. Since the lookups are only registered when the provider-driver binds, trying to get these clks/regulators before then results in a -ENOENT error for clks and a dummy regulator for regulators. One case where we hit this issue is camera sensors such as e.g. the OV8865 sensor found on the Microsoft Surface Go. The sensor uses clks, regulators and GPIOs provided by a TPS68470 PMIC which is described in an INT3472 ACPI device. There is special platform code handling this and setting platform_data with the necessary consumer info on the MFD cells instantiated for the PMIC under: drivers/platform/x86/intel/int3472. For this to work properly the ov8865 driver must not bind to the I2C-client for the OV8865 sensor until after the TPS68470 PMIC gpio, regulator and clk MFD cells have all been fully setup. The OV8865 on the Microsoft Surface Go is just one example, all X86 devices using the Intel IPU3 camera block found on recent Intel SoCs have similar issues where there is an INT3472 HID ACPI-device, which describes the clks and regulators, and the driver for this INT3472 device must be fully initialized before the sensor driver (any sensor driver) binds for things to work properly. On these devices the ACPI nodes describing the sensors all have a _DEP dependency on the matching INT3472 ACPI device (there is one per sensor). This allows solving the probe-ordering problem by delaying the enumeration (instantiation of the I2C-client in the ov8865 example) of ACPI-devices which have a _DEP dependency on an INT3472 device. The new acpi_dev_ready_for_enumeration() helper used for this is also exported because for devices, which have the enumeration_by_parent flag set, the parent-driver will do its own scan of child ACPI devices and it will try to enumerate those during its probe(). Code doing this such as e.g. the i2c-core-acpi.c code must call this new helper to ensure that it too delays the enumeration until all the _DEP dependencies are met on devices which have the new honor_deps flag set. Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com> Signed-off-by: Hans de Goede <hdegoede@redhat.com> Link: https://lore.kernel.org/r/20211203102857.44539-2-hdegoede@redhat.com |
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| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| 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 | ||
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.