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/Documentation/fujitsu/frv/clock.txt

https://bitbucket.org/evzijst/gittest
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 1Clock scaling
 2-------------
 3
 4The kernel supports scaling of CLCK.CMODE, CLCK.CM and CLKC.P0 clock
 5registers. If built with CONFIG_PM and CONFIG_SYSCTL options enabled, four
 6extra files will appear in the directory /proc/sys/pm/. Reading these files
 7will show:
 8
 9      p0		-- current value of the P0 bit in CLKC register.
10      cm		-- current value of the CM bits in CLKC register.
11      cmode		-- current value of the CMODE bits in CLKC register.
12
13On all boards, the 'p0' file should also be writable, and either '1' or '0'
14can be rewritten, to set or clear the CLKC_P0 bit respectively, hence
15controlling whether the resource bus rate clock is halved.
16
17The 'cm' file should also be available on all boards. '0' can be written to it
18to shift the board into High-Speed mode (normal), and '1' can be written to
19shift the board into Medium-Speed mode. Selecting Low-Speed mode is not
20supported by this interface, even though some CPUs do support it.
21
22On the boards with FR405 CPU (i.e. CB60 and CB70), the 'cmode' file is also
23writable, allowing the CPU core speed (and other clock speeds) to be
24controlled from userspace.
25
26
27Determining current and possible settings
28-----------------------------------------
29
30The current state and the available masks can be found in /proc/cpuinfo. For
31example, on the CB70:
32
33	# cat /proc/cpuinfo
34	CPU-Series:     fr400
35	CPU-Core:       fr405, gr0-31, BE, CCCR
36	CPU:            mb93405
37	MMU:            Prot
38	FP-Media:       fr0-31, Media
39	System:         mb93091-cb70, mb93090-mb00
40	PM-Controls:    cmode=0xd31f, cm=0x3, p0=0x3, suspend=0x9
41	PM-Status:      cmode=3, cm=0, p0=0
42	Clock-In:       50.00 MHz
43	Clock-Core:     300.00 MHz
44	Clock-SDRAM:    100.00 MHz
45	Clock-CBus:     100.00 MHz
46	Clock-Res:      50.00 MHz
47	Clock-Ext:      50.00 MHz
48	Clock-DSU:      25.00 MHz
49	BogoMips:       300.00
50
51And on the PDK, the PM lines look like the following:
52
53	PM-Controls:    cm=0x3, p0=0x3, suspend=0x9
54	PM-Status:      cmode=9, cm=0, p0=0
55
56The PM-Controls line, if present, will indicate which /proc/sys/pm files can
57be set to what values. The specification values are bitmasks; so, for example,
58"suspend=0x9" indicates that 0 and 3 can be written validly to
59/proc/sys/pm/suspend.
60
61The PM-Controls line will only be present if CONFIG_PM is configured to Y.
62
63The PM-Status line indicates which clock controls are set to which value. If
64the file can be read, then the suspend value must be 0, and so that's not
65included.