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Anson Huang authored
Some of i.MX8M SoCs have MU clock, they need to be managed in runtime
to make sure the MU clock can be off in runtime, add runtime PM callback
to handle MU clock.

And on i.MX8MP, the MU clock is combined with power domain and runtime
PM is enabled for the clock driver, during noirq suspend/resume phase,
runtime PM is disabled by device suspend, but the MU context save/restore
needs to enable MU clock for register access, calling clock prepare/enable
will trigger runtime resume failure and lead to system suspend failed.

Actually, the MU context save/restore is ONLY necessary for SCU IPC MU,
other MUs especially on i.MX8MP platforms which have MU clock assigned,
they need to runtime request/free mailbox channel in the consumer driver,
so no need to save/restore MU context for them, hence it can avoid this
issue, so the MU context save/restore is ONLY applied to i.MX platforms
MU instance without clock present.

Signed-off-by: default avatarAnson Huang <Anson.Huang@nxp.com>
Signed-off-by: default avatarJassi Brar <jaswinder.singh@linaro.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 Restructured Text 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.