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Currently, it is possible that LPM is enabled while calling the set_lpm() callback. The current code performs a SET FEATURES command to disable DIPM if policy < ATA_LPM_MED_POWER_WITH_DIPM, this means that it will currently disable DIPM for policies: ATA_LPM_UNKNOWN, ATA_LPM_MAX_POWER, ATA_LPM_MED_POWER (but not for policy ATA_LPM_MED_POWER_WITH_DIPM). The code called after calling the set_lpm() callback will later perform a SET FEATURES command to enable DIPM, if policy >= ATA_LPM_MED_POWER_WITH_DIPM. As we can see DIPM will not be disabled before calling set_lpm() if the LPM policy is: ATA_LPM_MED_POWER_WITH_DIPM, ATA_LPM_MIN_POWER_WITH_PARTIAL, or ATA_LPM_MIN_POWER. Make sure that we always disable DIPM before calling the set_lpm() callback. This is because the set_lpm() callback is the function (for AHCI) that sets the proper bits in PxSCTL.IPM, reflecting the support of the HBA. PxSCTL.IPM controls the LPM states that the device is allowed to enter. If the device tries to enter a state disabled by PxSCTL.IPM, the host will NAK the transition. If we do not disable DIPM before modifying PxSCTL.IPM, it is possible that DIPM will try (and will be allowed to) enter a LPM state that the HBA does not support (since we have not yet written PxSCTL.IPM, the HBA wasn't able to NAK the transition). While at it, remove the guard of host support for DIPM around the disabling of DIPM. While it makes sense to take host support for DIPM into account when enabling DIPM, it makes zero sense to take host support into account when disabling DIPM. If the host does not support DIPM, that is an even bigger reason why DIPM should be disabled on the device side. Signed-off-by: Niklas Cassel <cassel@kernel.org> Signed-off-by: Damien Le Moal <dlemoal@kernel.org> |
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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 reStructuredText 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.