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. 66