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Starting with MTL, the driver needs to not only protect the steering control register from simultaneous software accesses, but also protect against races with hardware/firmware agents. The hardware provides a dedicated locking mechanism to support this via the MTL_STEER_SEMAPHORE register. Reading the register acts as a 'trylock' operation; the read will return 0x1 if the lock is acquired or 0x0 if something else is already holding the lock; once acquired, writing 0x1 to the register will release the lock. We'll continue to grab the software lock as well, just so lockdep can track our locking; assuming the hardware lock is behaving properly, there should never be any contention on the software lock in this case. v2: - Extend hardware semaphore timeout and add a taint for CI if it ever happens (this would imply misbehaving hardware/firmware). (Mika) - Add "MTL_" prefix to new steering semaphore register. (Mika) Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com> Signed-off-by: Matt Roper <matthew.d.roper@intel.com> Reviewed-by: Balasubramani Vivekanandan <balasubramani.vivekanandan@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20221128233014.4000136-5-matthew.d.roper@intel.com
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.