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[ Upstream commitf4033db5b8] This is mostly a revert of commit55bb6a633c("clk: rockchip: mark noc and some special clk as critical on rk3288") except that we're keeping "pmu_hclk_otg0" as critical still. NOTE: turning these clocks off doesn't seem to do a whole lot in terms of power savings (checking the power on the logic rail). It appears to save maybe 1-2mW. ...but still it seems like we should turn the clocks off if they aren't needed. About "pmu_hclk_otg0" (the one clock from the original commit we're still keeping critical) from an email thread: > pmu ahb clock > > Function: Clock to pmu module when hibernation and/or ADP is > enabled. Must be greater than or equal to 30 MHz. > > If the SOC design does not support hibernation/ADP function, only have > hclk_otg, this clk can be switched according to the usage of otg. > If the SOC design support hibernation/ADP, has two clocks, hclk_otg and > pmu_hclk_otg0. > Hclk_otg belongs to the closed part of otg logic, which can be switched > according to the use of otg. > > pmu_hclk_otg0 belongs to the always on part. > > As for whether pmu_hclk_otg0 can be turned off when otg is not in use, > we have not tested. IC suggest make pmu_hclk_otg0 always on. For the rest of the clocks: atclk: No documentation about this clock other than that it goes to the CPU. CPU functions fine without it on. Maybe needed for JTAG? jtag: Presumably this clock is only needed if you're debugging with JTAG. It doesn't seem like it makes sense to waste power for every rk3288 user. In any case to do JTAG you'd need private patches to adjust the pinctrl the mux the JTAG out anyway. pclk_dbg, pclk_core_niu: On veyron Chromebooks we turn these two clocks on only during kernel panics in order to access some coresight registers. Since nothing in the upstream kernel does this we should be able to leave them off safely. Maybe also needed for JTAG? hsicphy12m_xin12m: There is no indication of why this clock would need to be turned on for boards that don't use HSIC. pclk_ddrupctl[0-1], pclk_publ0[0-1]: On veyron Chromebooks we turn these 4 clocks on only when doing DDR transitions and they are off otherwise. I see no reason why they'd need to be on in the upstream kernel which doesn't support DDRFreq. Signed-off-by: Douglas Anderson <dianders@chromium.org> Reviewed-by: Elaine Zhang <zhangqing@rock-chips.com> Signed-off-by: Heiko Stuebner <heiko@sntech.de> Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.