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We make use of common imx8m_suspend / imx8m_resume functions for both system PM and runtime PM. imx8m_suspend: - frees the MU channels - disables the clocks imx8m_resume - enables the clocks - requests the MU channels On i.MX8MP there is no dedicated functionality to put the DSP in reset. The only way of doing this is to POWER DOWN the Audiomix domain. We are able to do this because turning off the clocks and freeing the channels makes the Audiomix to have no users thus PM kernel core turns it down. SOF core will not call system PM suspend handler if the DSP is already down, but at resume it will call the system PM resume. So, we need to keep track of the state via snd_sof_dsp_set_power_state Few insights on how SOF core handles the PM: - SOF core uses PM runtime autosuspend (with a timeout of 2 secs) - at probe, SOF core boots the DSP and lets the PM runtime suspend to turn it off, if there is no activity - when someone opens the ALSA sound card (aplay/arecord, etc) ALSA core calls PM runtime resume to turn on the DSP - when the ALSA sound card is closed SOF core make use of PM subsystem to call PM runtime suspend and thus turning off the DSP. Signed-off-by: Daniel Baluta <daniel.baluta@nxp.com> Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com> Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com> Link: https://lore.kernel.org/r/20211119094319.81674-4-daniel.baluta@oss.nxp.com Signed-off-by: Mark Brown <broonie@kernel.org>
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.