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acrn-kernel/Documentation/arm/sunxi/clocks.rst

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docs: arm: convert docs to ReST and rename to *.rst Converts ARM the text files to ReST, preparing them to be an architecture book. The conversion is actually: - add blank lines and identation in order to identify paragraphs; - fix tables markups; - add some lists markups; - mark literal blocks; - adjust title markups. At its new index.rst, let's add a :orphan: while this is not linked to the main index.rst file, in order to avoid build warnings. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Reviewed-by Corentin Labbe <clabbe.montjoie@gmail.com> # For sun4i-ss
2019-04-15 02:51:10 +08:00
=======================================================
arm: sunxi: Add useful information about sunxi clocks This patch contains useful bits of information about the sunxi clocks that may help and/or be interesting for current and future developers. Signed-off-by: Emilio López <emilio@elopez.com.ar> Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com> Signed-off-by: Mike Turquette <mturquette@linaro.org>
2013-02-25 22:44:28 +08:00
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:
docs: arm: convert docs to ReST and rename to *.rst Converts ARM the text files to ReST, preparing them to be an architecture book. The conversion is actually: - add blank lines and identation in order to identify paragraphs; - fix tables markups; - add some lists markups; - mark literal blocks; - adjust title markups. At its new index.rst, let's add a :orphan: while this is not linked to the main index.rst file, in order to avoid build warnings. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Reviewed-by Corentin Labbe <clabbe.montjoie@gmail.com> # For sun4i-ss
2019-04-15 02:51:10 +08:00
While the system is operational, you would see something like::
arm: sunxi: Add useful information about sunxi clocks This patch contains useful bits of information about the sunxi clocks that may help and/or be interesting for current and future developers. Signed-off-by: Emilio López <emilio@elopez.com.ar> Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com> Signed-off-by: Mike Turquette <mturquette@linaro.org>
2013-02-25 22:44:28 +08:00
24MHz 32kHz
|
PLL1
\
\_ CPU Mux
|
[CPU]
When you are about to suspend, you switch the CPU Mux to the 32kHz
docs: arm: convert docs to ReST and rename to *.rst Converts ARM the text files to ReST, preparing them to be an architecture book. The conversion is actually: - add blank lines and identation in order to identify paragraphs; - fix tables markups; - add some lists markups; - mark literal blocks; - adjust title markups. At its new index.rst, let's add a :orphan: while this is not linked to the main index.rst file, in order to avoid build warnings. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Reviewed-by Corentin Labbe <clabbe.montjoie@gmail.com> # For sun4i-ss
2019-04-15 02:51:10 +08:00
oscillator::
arm: sunxi: Add useful information about sunxi clocks This patch contains useful bits of information about the sunxi clocks that may help and/or be interesting for current and future developers. Signed-off-by: Emilio López <emilio@elopez.com.ar> Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com> Signed-off-by: Mike Turquette <mturquette@linaro.org>
2013-02-25 22:44:28 +08:00
24Mhz 32kHz
| |
PLL1 |
/
CPU Mux _/
|
[CPU]
docs: arm: convert docs to ReST and rename to *.rst Converts ARM the text files to ReST, preparing them to be an architecture book. The conversion is actually: - add blank lines and identation in order to identify paragraphs; - fix tables markups; - add some lists markups; - mark literal blocks; - adjust title markups. At its new index.rst, let's add a :orphan: while this is not linked to the main index.rst file, in order to avoid build warnings. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Reviewed-by Corentin Labbe <clabbe.montjoie@gmail.com> # For sun4i-ss
2019-04-15 02:51:10 +08:00
Finally you can gate the main oscillator::
arm: sunxi: Add useful information about sunxi clocks This patch contains useful bits of information about the sunxi clocks that may help and/or be interesting for current and future developers. Signed-off-by: Emilio López <emilio@elopez.com.ar> Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com> Signed-off-by: Mike Turquette <mturquette@linaro.org>
2013-02-25 22:44:28 +08:00
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