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Somehow the existing code is not aligned with the steps described in the documentation, refactor code and make sure the register programming sequences are correct. Also add missing power-up, power-down and wake capabilities (the last two are used in follow-up patches but introduced here for consistency). Some of the SHIM registers exposed fields that are link specific, and in addition some of the power-related registers (SPA/CPA) take time to be updated. Uncontrolled access leads to timeouts or errors. Add a mutex, shared by all links, so that all accesses to such registers are serialized, and follow a pattern of read-modify-write. This includes making sure SHIM_SYNC is programmed only once, before the first master is powered on. We use a 'shim_mask' field, shared between all links and protected by a mutex, to deal with power-up and power-down sequences. Note that the SYNCPRD value is tied only to the XTAL value and not the current bus frequency or the frame rate. BugLink: https://github.com/thesofproject/linux/issues/1555 Signed-off-by: Rander Wang <rander.wang@intel.com> Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com> Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com> Link: https://lore.kernel.org/r/20200716150947.22119-3-yung-chuan.liao@linux.intel.com Signed-off-by: Vinod Koul <vkoul@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.