8110dd281e
Some recent Dell laptops, including the XPS13 model numbers 9360 and 9365, cannot be woken up from suspend-to-idle by pressing the power button which is unexpected and makes that feature less usable on those systems. Moreover, on the 9365 ACPI S3 (suspend-to-RAM) is not expected to be used at all (the OS these systems ship with never exercises the ACPI S3 path in the firmware) and suspend-to-idle is the only viable system suspend mechanism there. The reason why the power button wakeup from suspend-to-idle doesn't work on those systems is because their power button events are signaled by the EC (Embedded Controller), whose GPE (General Purpose Event) line is disabled during suspend-to-idle transitions in Linux. That is done on purpose, because in general the EC tends to be noisy for various reasons (battery and thermal updates and similar, for example) and all events signaled by it would kick the CPUs out of deep idle states while in suspend-to-idle, which effectively might defeat its purpose. Of course, on the Dell systems in question the EC GPE must be enabled during suspend-to-idle transitions for the button press events to be signaled while suspended at all, but fortunately there is a way out of this puzzle. First of all, those systems have the ACPI_FADT_LOW_POWER_S0 flag set in their ACPI tables, which means that the OS is expected to prefer the "low power S0 idle" system state over ACPI S3 on them. That causes the most recent versions of other OSes to simply ignore ACPI S3 on those systems, so it is reasonable to expect that it should not be necessary to block GPEs during suspend-to-idle on them. Second, in addition to that, the systems in question provide a special firmware interface that can be used to indicate to the platform that the OS is transitioning into a system-wide low-power state in which certain types of activity are not desirable or that it is leaving such a state and that (in principle) should allow the platform to adjust its operation mode accordingly. That interface is a special _DSM object under a System Power Management Controller device (PNP0D80). The expected way to use it is to invoke function 0 from it on system initialization, functions 3 and 5 during suspend transitions and functions 4 and 6 during resume transitions (to reverse the actions carried out by the former). In particular, function 5 from the "Low-Power S0" device _DSM is expected to cause the platform to put itself into a low-power operation mode which should include making the EC less verbose (so to speak). Next, on resume, function 6 switches the platform back to the "working-state" operation mode. In accordance with the above, modify the ACPI suspend-to-idle code to look for the "Low-Power S0" _DSM interface on platforms with the ACPI_FADT_LOW_POWER_S0 flag set in the ACPI tables. If it's there, use it during suspend-to-idle transitions as prescribed and avoid changing the GPE configuration in that case. [That should reflect what the most recent versions of other OSes do.] Also modify the ACPI EC driver to make it handle events during suspend-to-idle in the usual way if the "Low-Power S0" _DSM interface is going to be used to make the power button events work while suspended on the Dell machines mentioned above Link: http://www.uefi.org/sites/default/files/resources/Intel_ACPI_Low_Power_S0_Idle.pdf Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> |
||
|---|---|---|
| Documentation | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| firmware | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
README
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.