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It's not required to traverse the entire clk tree when the parents array contains a NULL value. We already have the parent clk_core pointer, so we can just compare the parent->name and parent_names[i] pointers. This can be a substantial power improvement in cases where the parent clk isn't known and that clk is never registered, because a mux having an unregistered parent name may traverse the clk tree on every clk_set_rate() call in clk_mux_determine_rate_flags(). This can happen hundreds of times a second for CPU clks. This patch is the combination of reverting commit470b5e2f97("clk: simplify clk_fetch_parent_index() function") and optimizing the resulting code to never call __clk_lookup() because we already have the clk_core pointer we're looking for. That optimization went unnoticed even after commitda0f0b2c3a("clk: Correct lookup logic in clk_fetch_parent_index()") tried to optimize this path. Signed-off-by: Derek Basehore <dbasehore@chromium.org> [sboyd@kernel.org: More description in commit text] Signed-off-by: Stephen Boyd <sboyd@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.