i.MX51 EVK Linux Reference Manual
Freescale Semiconductor
8-1
Chapter 8
Dynamic Voltage Frequency Scaling (DVFS) Driver
The Dynamic Voltage Frequency Scaling (DVFS) device driver allows simple dynamic voltage frequency
scaling. The frequency of the core (CPU) clock domain and the voltage of the core power domain can be
changed on the fly with all modules continuing their normal operations. The voltage of the core power
domain can be changed through the PMIC. The frequency of the core clock domain can be changed by
switching temporarily to an alternate PLL clock, and then returning to the updated PLL, already locked at
a specific frequency, or by merely changing the post dividers division factors.
8.1
Hardware Operation
The DVFS core module is a power management module. The purpose of the DVFS module is to detect the
appropriate operation frequency for the IC. DVFS core is operated under control of the GPC (General
Power Controller) block. The hardware DVFS core interrupt is served by GPC IRQ. The DVFS core
domain performance update procedure includes both voltage and frequency changes in appropriate order
by the GPC controller (hardware). For more information on the HW DVFS Core block refer to the DVFS
chapter in the
Multimedia Applications Processor
documentation.
8.2
Software Operation
The DVFS device driver allows the frequency of the core clock domain and the voltage of the core power
domain to be changed on the fly. The frequency of the core clock domain and the voltage of the core power
domain are changed by switching between defined freq-voltage operating points. The frequencies are
manipulated using the clock framework API, while the voltage is set using the regulators API. The CPU
frequencies in the array are based on the boot CPU frequency which can be changed using the clock
command in RedBoot.
To Enable the DVFS core use this command:
echo 1 > /sys/devices/platform/mxc_dvfs_core.0/enable
To Disable The DVFS core use this command:
echo 0 > /sys/devices/platform/mxc_dvfs_core.0/enable
Summary of Contents for i.MX51 EVK
Page 1: ...Part Number 924 76374 Rev 10 11 01 11 2010 i MX51 EVK Linux Reference Manual...
Page 14: ...i MX51 EVK Linux Reference Manual xiv Freescale Semiconductor...
Page 18: ...i MX51 EVK Linux Reference Manual xviii Freescale Semiconductor...
Page 24: ...i MX51 EVK Linux Reference Manual xxiv Freescale Semiconductor...
Page 38: ...Machine Specific Layer MSL i MX51 EVK Linux Reference Manual 2 8 Freescale Semiconductor...
Page 52: ...MC13892 Digitizer Driver i MX51 EVK Linux Reference Manual 5 4 Freescale Semiconductor...
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Page 100: ...X Windows Acceleration i MX51 EVK Linux Reference Manual 16 6 Freescale Semiconductor...
Page 118: ...Low Level Keypad Driver i MX51 EVK Linux Reference Manual 20 6 Freescale Semiconductor...
Page 134: ...Security Drivers i MX51 EVK Linux Reference Manual 22 10 Freescale Semiconductor...
Page 148: ...Inter IC I2C Driver i MX51 EVK Linux Reference Manual 24 4 Freescale Semiconductor...
Page 178: ...ARC USB Driver i MX51 EVK Linux Reference Manual 29 10 Freescale Semiconductor...
Page 194: ...OProfile i MX51 EVK Linux Reference Manual 33 6 Freescale Semiconductor...
