• Tejun Heo's avatar
    libata: reimplement link power management · 6b7ae954
    Tejun Heo authored
    The current LPM implementation has the following issues.
    * Operation order isn't well thought-out.  e.g. HIPM should be
      configured after IPM in SControl is properly configured.  Not the
      other way around.
    * Suspend/resume paths call ata_lpm_enable/disable() which must only
      be called from EH context directly.  Also, ata_lpm_enable/disable()
      were called whether LPM was in use or not.
    * Implementation is per-port when it should be per-link.  As a result,
      it can't be used for controllers with slave links or PMP.
    * LPM state isn't managed consistently.  After a link reset for
      whatever reason including suspend/resume the actual LPM state would
      be reset leaving ap->lpm_policy inconsistent.
    * Generic/driver-specific logic boundary isn't clear.  Currently,
      libahci has to mangle stuff which libata EH proper should be
      handling.  This makes the implementation unnecessarily complex and
    * Tied to ALPM.  Doesn't consider DIPM only cases and doesn't check
      whether the device allows HIPM.
    * Error handling isn't implemented.
    Given the extent of mismatch with the rest of libata, I don't think
    trying to fix it piecewise makes much sense.  This patch reimplements
    LPM support.
    * The new implementation is per-link.  The target policy is still
      port-wide (ap->target_lpm_policy) but all the mechanisms and states
      are per-link and integrate well with the rest of link abstraction
      and can work with slave and PMP links.
    * Core EH has proper control of LPM state.  LPM state is reconfigured
      when and only when reconfiguration is necessary.  It makes sure that
      LPM state is reset when probing for new device on the link.
      Controller agnostic logic is now implemented in libata EH proper and
      driver implementation only has to deal with controller specifics.
    * Proper error handling.  LPM config failure is attributed to the
      device on the link and LPM is disabled for the link if it fails
    * ops->enable/disable_pm() are replaced with single ops->set_lpm()
      which takes @policy and @hints.  This simplifies driver specific
    Signed-off-by: default avatarTejun Heo <tj@kernel.org>
    Signed-off-by: default avatarJeff Garzik <jgarzik@redhat.com>
ahci_platform.c 4.6 KB