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authorMeizu OpenSource <patchwork@meizu.com>2016-08-15 10:19:42 +0800
committerMeizu OpenSource <patchwork@meizu.com>2016-08-15 10:19:42 +0800
commitd2e1446d81725c351dc73a03b397ce043fb18452 (patch)
tree4dbc616b7f92aea39cd697a9084205ddb805e344 /Documentation/arm/sunxi
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-rw-r--r--Documentation/arm/sunxi/clocks.txt56
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diff --git a/Documentation/arm/sunxi/README b/Documentation/arm/sunxi/README
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+ARM Allwinner SoCs
+==================
+
+This document lists all the ARM Allwinner SoCs that are currently
+supported in mainline by the Linux kernel. This document will also
+provide links to documentation and or datasheet for these SoCs.
+
+SunXi family
+------------
+
+ Flavors:
+ Allwinner A10 (sun4i)
+ Datasheet : http://dl.linux-sunxi.org/A10/A10%20Datasheet%20-%20v1.21%20%282012-04-06%29.pdf
+
+ Allwinner A13 (sun5i)
+ Datasheet : http://dl.linux-sunxi.org/A13/A13%20Datasheet%20-%20v1.12%20%282012-03-29%29.pdf
+
+ Core: Cortex A8
+ Linux kernel mach directory: arch/arm/mach-sunxi \ No newline at end of file
diff --git a/Documentation/arm/sunxi/clocks.txt b/Documentation/arm/sunxi/clocks.txt
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+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