2da4c5e24e
Improve the function ata_dev_power_set_active() by having it do nothing for a disk that is already in the active power state. To do that, introduce the function ata_dev_power_is_active() to test the current power state of the disk and return true if the disk is in the PM0: active or PM1: idle state (0xff value for the count field of the CHECK POWER MODE command output). To preserve the existing behavior, if the CHECK POWER MODE command issued in ata_dev_power_is_active() fails, the drive is assumed to be in standby mode and false is returned. With this change, issuing the VERIFY command to access the disk media to spin it up becomes unnecessary most of the time during system resume as the port reset done by libata-eh on resume often result in the drive to spin-up (this behavior is not clearly defined by the ACS specifications and may thus vary between disk models). Signed-off-by: Damien Le Moal <dlemoal@kernel.org> Tested-by: Geert Uytterhoeven <geert+renesas@glider.be> Reviewed-by: Niklas Cassel <niklas.cassel@wdc.com>
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.