Comment 3 for bug 1488426

The commit fixes the issue

commit 9250aea76bfcbf4c2a7868e5566281bf2bb7af27
Author: Ulf Hansson <email address hidden>
Date: Fri Mar 27 12:15:15 2015 +0100

    mmc: core: Enable runtime PM management of host devices

    Currently those host drivers which have deployed runtime PM, deals with
    the runtime PM reference counting entirely by themselves.

    Since host drivers don't know when the core will send the next request
    through some of the host_ops callbacks, they need to handle runtime PM
    get/put between each an every request.

    In quite many cases this has some negative effects, since it leads to a
    high frequency of scheduled runtime PM suspend operations. That due to
    the runtime PM reference count will normally reach zero in-between
    every request.

    We can decrease that frequency, by enabling the core to deal with
    runtime PM reference counting of the host device. Since the core often
    knows that it will send a seqeunce of requests, it makes sense for it
    to keep a runtime PM reference count during these periods.

    More exactly, let's increase the runtime PM reference count by invoking
    pm_runtime_get_sync() from __mmc_claim_host(). Restore that action by
    invoking pm_runtime_mark_last_busy() and pm_runtime_put_autosuspend()
    in mmc_release_host(). In this way a runtime PM reference count will be
    kept during the complete cycle of a claim -> release host.

    Signed-off-by: Ulf Hansson <email address hidden>
    Acked-by: Adrian Hunter <email address hidden>
    Acked-by: Konstantin Dorfman <email address hidden>