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While we talk to the punit over its sideband, we need to prevent the cpu from sleeping in order to prevent a potential machine hang. Note that by itself, it appears that pm_qos_update_request (via intel_idle) doesn't provide a sufficient barrier to ensure that all core are indeed awake (out of Cstate) and that the package is awake. To do so, we need to supplement the pm_qos with a manual ping on_each_cpu. v2: Restrict the heavy-weight wakeup to just the ISOF_PORT_PUNIT, there is insufficient evidence to implicate a wider problem atm. Similarly, restrict the w/a to Valleyview, as Cherryview doesn't have an angry cadre of users. The working theory, courtesy of Ville and Hans, is the issue lies within the power delivery and so is likely to be unit and board specific and occurs when both the unit/fw require extra power at the same time as the cpu package is changing its own power state. References: https://bugzilla.kernel.org/show_bug.cgi?id=109051 References: https://bugs.freedesktop.org/show_bug.cgi?id=102657 References: https://bugzilla.kernel.org/show_bug.cgi?id=195255 Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com> Cc: Hans de Goede <hdegoede@redhat.com> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com> Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20190426081725.31217-1-chris@chris-wilson.co.uk
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.