• Rafael J. Wysocki's avatar
    PM / QoS: Fix device resume latency PM QoS · 0cc2b4e5
    Rafael J. Wysocki authored
    The special value of 0 for device resume latency PM QoS means
    "no restriction", but there are two problems with that.
    
    First, device resume latency PM QoS requests with 0 as the
    value are always put in front of requests with positive
    values in the priority lists used internally by the PM QoS
    framework, causing 0 to be chosen as an effective constraint
    value.  However, that 0 is then interpreted as "no restriction"
    effectively overriding the other requests with specific
    restrictions which is incorrect.
    
    Second, the users of device resume latency PM QoS have no
    way to specify that *any* resume latency at all should be
    avoided, which is an artificial limitation in general.
    
    To address these issues, modify device resume latency PM QoS to
    use S32_MAX as the "no constraint" value and 0 as the "no
    latency at all" one and rework its users (the cpuidle menu
    governor, the genpd QoS governor and the runtime PM framework)
    to follow these changes.
    
    Also add a special "n/a" value to the corresponding user space I/F
    to allow user space to indicate that it cannot accept any resume
    latencies at all for the given device.
    
    Fixes: 85dc0b8a (PM / QoS: Make it possible to expose PM QoS latency constraints)
    Link: https://bugzilla.kernel.org/show_bug.cgi?id=197323Reported-by: default avatarReinette Chatre <reinette.chatre@intel.com>
    Tested-by: default avatarReinette Chatre <reinette.chatre@intel.com>
    Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
    Acked-by: default avatarAlex Shi <alex.shi@linaro.org>
    Cc: All applicable <stable@vger.kernel.org>
    0cc2b4e5
cpu.c 12 KB