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On many laptops setting a different LPM policy then unknown / max_performance can lead to power-savings of 1.0 - 1.5 Watts (when idle). Modern ultrabooks idle around 6W (at 50% screen brightness), 1.0 - 1.5W is a significant chunk of this. There are some performance / latency costs to enabling LPM by default, so it is desirable to make it possible to set a different LPM policy for mobile / laptop variants of chipsets / "South Bridges" vs their desktop / server counterparts. Also enabling LPM by default is not entirely without risk of regressions. At least min_power is known to cause issues with some disks, including some reports of data corruption. This commits adds a new ahci.mobile_lpm_policy kernel cmdline option, which defaults to a new SATA_MOBILE_LPM_POLICY Kconfig option so that Linux distributions can choose to set a LPM policy for mobile chipsets by default. The reason to have both a kernel cmdline option and a Kconfig default value for it, is to allow easy overriding of the default to allow trouble-shooting without needing to rebuild the kernel. Signed-off-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Tejun Heo <tj@kernel.org>
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.