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Mainline Linux tree for various devices, only for fun :)
7cbb78a99d
The function clk_gfx3d_determine_rate is selecting different PLLs to manage the GFX3D clock source in a special way: this one needs to be ping-pong'ed on different PLLs to ensure stability during frequency switching (set a PLL rate, let it stabilize, switch the RCG to the new PLL) and fast frequency transitions. This technique is currently being used in the MSM8996 SoC and the function was assuming that the parents were always at a specific index in the parents list, which is TRUE, if we use this only on the MSM8996 MMCC. Unfortunately, MSM8996 is not the only SoC that needs to ping-pong the graphics RCG, so choices are: 1. Make new special ops just to hardcode *again* other indexes, creating code duplication for (imo) no reason; or 2. Generalize this function, so that it becomes usable for a range of SoCs with slightly different ping-pong configuration. In this commit, the second road was taken: define a new "special" struct clk_rcg2_gfx3d, containing the ordered list of parents to ping-pong the graphics clock on, and the "regular" rcg2 clock structure in order to generalize the clk_gfx3d_determine_rate function and make it working for other SoCs. As for the function itself it is left with the assumption that we need to ping-pong over three parents. The reasons for this are: 1. The initial model was MSM8996, which has 3 parents for the graphics clock pingpong; 2. The other example that was taken into consideration is the SDM630/636/660 SoC gpu clock controller, which is ping-ponging over two dynamic clocked and one fixed clock PLL. Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@somainline.org> Link: https://lore.kernel.org/r/20210113183817.447866-6-angelogioacchino.delregno@somainline.org [sboyd@kernel.org: Grow some local variables, drop do_div() usage in favor of plain division, we're not dealing with a u64 here] Signed-off-by: Stephen Boyd <sboyd@kernel.org> |
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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.