• Subhash Jadavani's avatar
    ufs: add UFS power management support · 57d104c1
    Subhash Jadavani authored
    This patch adds support for UFS device and UniPro link power management
    during runtime/system PM.
    
    Main idea is to define multiple UFS low power levels based on UFS device
    and UFS link power states. This would allow any specific platform or pci
    driver to choose the best suited low power level during runtime and
    system suspend based on their power goals.
    
    bkops handlig:
    To put the UFS device in sleep state when bkops is disabled, first query
    the bkops status from the device and enable bkops on device only if
    device needs time to perform the bkops.
    
    START_STOP handling:
    Before sending START_STOP_UNIT to the device well-known logical unit
    (w-lun) to make sure that the device w-lun unit attention condition is
    cleared.
    
    Write protection:
    UFS device specification allows LUs to be write protected, either
    permanently or power on write protected. If any LU is power on write
    protected and if the card is power cycled (by powering off VCCQ and/or
    VCC rails), LU's write protect status would be lost. So this means those
    LUs can be written now. To ensures that UFS device is power cycled only
    if the power on protect is not set for any of the LUs, check if power on
    write protect is set and if device is in sleep/power-off state & link in
    inactive state (Hibern8 or OFF state).
    If none of the Logical Units on UFS device is power on write protected
    then all UFS device power rails (VCC, VCCQ & VCCQ2) can be turned off if
    UFS device is in power-off state and UFS link is in OFF state. But current
    implementation would disable all device power rails even if UFS link is
    not in OFF state.
    
    Low power mode:
    If UFS link is in OFF state then UFS host controller can be power collapsed
    to avoid leakage current from it. Note that if UFS host controller is power
    collapsed, full UFS reinitialization will be required on resume to
    re-establish the link between host and device.
    Signed-off-by: default avatarSubhash Jadavani <subhashj@codeaurora.org>
    Signed-off-by: default avatarDolev Raviv <draviv@codeaurora.org>
    Signed-off-by: default avatarSujit Reddy Thumma <sthumma@codeaurora.org>
    Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
    57d104c1
ufshcd-pltfrm.c 9.9 KB