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author | Frederic Weisbecker <fweisbec@gmail.com> | 2013-05-02 17:37:49 +0200 |
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committer | Frederic Weisbecker <fweisbec@gmail.com> | 2013-05-02 17:54:19 +0200 |
commit | c032862fba51a3ca504752d3a25186b324c5ce83 (patch) | |
tree | 955dc2ba4ab3df76ecc2bb780ee84aca04967e8d /Documentation/arm | |
parent | Merge branch 'rcu/nohz' of git://git.kernel.org/pub/scm/linux/kernel/git/paul... (diff) | |
parent | Merge branch 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/ke... (diff) | |
download | linux-c032862fba51a3ca504752d3a25186b324c5ce83.tar.xz linux-c032862fba51a3ca504752d3a25186b324c5ce83.zip |
Merge commit '8700c95adb03' into timers/nohz
The full dynticks tree needs the latest RCU and sched
upstream updates in order to fix some dependencies.
Merge a common upstream merge point that has these
updates.
Conflicts:
include/linux/perf_event.h
kernel/rcutree.h
kernel/rcutree_plugin.h
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Diffstat (limited to 'Documentation/arm')
-rw-r--r-- | Documentation/arm/sunxi/clocks.txt | 56 |
1 files changed, 56 insertions, 0 deletions
diff --git a/Documentation/arm/sunxi/clocks.txt b/Documentation/arm/sunxi/clocks.txt new file mode 100644 index 000000000000..e09a88aa3136 --- /dev/null +++ b/Documentation/arm/sunxi/clocks.txt @@ -0,0 +1,56 @@ +Frequently asked questions about the sunxi clock system +======================================================= + +This document contains useful bits of information that people tend to ask +about the sunxi clock system, as well as accompanying ASCII art when adequate. + +Q: Why is the main 24MHz oscillator gatable? Wouldn't that break the + system? + +A: The 24MHz oscillator allows gating to save power. Indeed, if gated + carelessly the system would stop functioning, but with the right + steps, one can gate it and keep the system running. Consider this + simplified suspend example: + + While the system is operational, you would see something like + + 24MHz 32kHz + | + PLL1 + \ + \_ CPU Mux + | + [CPU] + + When you are about to suspend, you switch the CPU Mux to the 32kHz + oscillator: + + 24Mhz 32kHz + | | + PLL1 | + / + CPU Mux _/ + | + [CPU] + + Finally you can gate the main oscillator + + 32kHz + | + | + / + CPU Mux _/ + | + [CPU] + +Q: Were can I learn more about the sunxi clocks? + +A: The linux-sunxi wiki contains a page documenting the clock registers, + you can find it at + + http://linux-sunxi.org/A10/CCM + + The authoritative source for information at this time is the ccmu driver + released by Allwinner, you can find it at + + https://github.com/linux-sunxi/linux-sunxi/tree/sunxi-3.0/arch/arm/mach-sun4i/clock/ccmu |