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authorLinus Torvalds <torvalds@linux-foundation.org>2008-02-04 18:58:52 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2008-02-04 18:58:52 +0300
commitf5bb3a5e9dcdb8435471562b6cada89525cf4df1 (patch)
tree7b7cf9b90bacd0e2fe07cb3387516e9243f1ab66 /Documentation/frv/clock.txt
parent9853832c49dc1685587abeb4e1decd4be690d256 (diff)
parent1560a79a2c2ea0c3826150da8029991d685de990 (diff)
downloadlinux-f5bb3a5e9dcdb8435471562b6cada89525cf4df1.tar.xz
Merge git://git.kernel.org/pub/scm/linux/kernel/git/bunk/trivial
* git://git.kernel.org/pub/scm/linux/kernel/git/bunk/trivial: (79 commits) Jesper Juhl is the new trivial patches maintainer Documentation: mention email-clients.txt in SubmittingPatches fs/binfmt_elf.c: spello fix do_invalidatepage() comment typo fix Documentation/filesystems/porting fixes typo fixes in net/core/net_namespace.c typo fix in net/rfkill/rfkill.c typo fixes in net/sctp/sm_statefuns.c lib/: Spelling fixes kernel/: Spelling fixes include/scsi/: Spelling fixes include/linux/: Spelling fixes include/asm-m68knommu/: Spelling fixes include/asm-frv/: Spelling fixes fs/: Spelling fixes drivers/watchdog/: Spelling fixes drivers/video/: Spelling fixes drivers/ssb/: Spelling fixes drivers/serial/: Spelling fixes drivers/scsi/: Spelling fixes ...
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+Clock scaling
+-------------
+
+The kernel supports scaling of CLCK.CMODE, CLCK.CM and CLKC.P0 clock
+registers. If built with CONFIG_PM and CONFIG_SYSCTL options enabled, four
+extra files will appear in the directory /proc/sys/pm/. Reading these files
+will show:
+
+ p0 -- current value of the P0 bit in CLKC register.
+ cm -- current value of the CM bits in CLKC register.
+ cmode -- current value of the CMODE bits in CLKC register.
+
+On all boards, the 'p0' file should also be writable, and either '1' or '0'
+can be rewritten, to set or clear the CLKC_P0 bit respectively, hence
+controlling whether the resource bus rate clock is halved.
+
+The 'cm' file should also be available on all boards. '0' can be written to it
+to shift the board into High-Speed mode (normal), and '1' can be written to
+shift the board into Medium-Speed mode. Selecting Low-Speed mode is not
+supported by this interface, even though some CPUs do support it.
+
+On the boards with FR405 CPU (i.e. CB60 and CB70), the 'cmode' file is also
+writable, allowing the CPU core speed (and other clock speeds) to be
+controlled from userspace.
+
+
+Determining current and possible settings
+-----------------------------------------
+
+The current state and the available masks can be found in /proc/cpuinfo. For
+example, on the CB70:
+
+ # cat /proc/cpuinfo
+ CPU-Series: fr400
+ CPU-Core: fr405, gr0-31, BE, CCCR
+ CPU: mb93405
+ MMU: Prot
+ FP-Media: fr0-31, Media
+ System: mb93091-cb70, mb93090-mb00
+ PM-Controls: cmode=0xd31f, cm=0x3, p0=0x3, suspend=0x9
+ PM-Status: cmode=3, cm=0, p0=0
+ Clock-In: 50.00 MHz
+ Clock-Core: 300.00 MHz
+ Clock-SDRAM: 100.00 MHz
+ Clock-CBus: 100.00 MHz
+ Clock-Res: 50.00 MHz
+ Clock-Ext: 50.00 MHz
+ Clock-DSU: 25.00 MHz
+ BogoMips: 300.00
+
+And on the PDK, the PM lines look like the following:
+
+ PM-Controls: cm=0x3, p0=0x3, suspend=0x9
+ PM-Status: cmode=9, cm=0, p0=0
+
+The PM-Controls line, if present, will indicate which /proc/sys/pm files can
+be set to what values. The specification values are bitmasks; so, for example,
+"suspend=0x9" indicates that 0 and 3 can be written validly to
+/proc/sys/pm/suspend.
+
+The PM-Controls line will only be present if CONFIG_PM is configured to Y.
+
+The PM-Status line indicates which clock controls are set to which value. If
+the file can be read, then the suspend value must be 0, and so that's not
+included.