System with feature of saving dynamic power of flip-flop banks
View Patent ↗A system comprises a first plurality of flip-flop circuits, a second plurality of flip-flop circuits, and a gating control module. At a first processor frequency, gating of clock signals is enabled for the first and second plurality of flip-flop circuits. At a second processor frequency, gating of a first of the clock signals is disabled for the first plurality of flip-flop circuits and gating of a second of the clock signals is enabled for the second plurality of flip-flop circuits.
1. A system comprising:
a first plurality of flip-flop circuits associated with a first threshold frequency above which a setup time requirement for the first plurality of flip-flop circuits is not met;
a second plurality of flip-flop circuits associated with a second threshold frequency above which a setup time requirement for the second plurality of flip-flop circuits is not met; and
a gating control module operable to:
enable gating of clock signals for the first and second plurality of flip-flop circuits in response to operation of a processor of the system at a first processor frequency that is below both the first threshold frequency and the second threshold frequency, wherein
the gating control module is configured to:
receive an indicator of the first processor frequency,
compare the indicator of the first processor frequency to an identifier of the first threshold frequency at or below which gating can be enabled for the first plurality of flip-flop circuits, and
set a first gating enable signal for the first plurality of flip-flop circuits based on whether the identifier of the first threshold frequency is higher than the indicator of the first processor frequency; and
disable gating of a first of the clock signals for the first plurality of flip-flop circuits in response to operation of the processor at a second processor frequency that is above the first threshold frequency and enable gating of a second of the clock signals for the second plurality of flip-flop circuits in response to the second processor frequency being below the second threshold frequency.
2. The system of claim 1 wherein the gating control module is further operable to:
disable gating of the first of the clock signals for the first plurality of flip-flop circuits before the processor transitions from the first processor frequency to the second processor frequency.
3. The system of claim 1 wherein the gating control module is further operable to:
enable gating of the second of the clock signals for the second plurality of flip-flop circuits after the processor transitions from the first processor frequency to the second processor frequency.
4. The system of claim 1 wherein the gating control module is further operable to:
disable gating of the clock signals for the first and second plurality of flip-flop circuits at a third processor frequency.
5. The system of claim 1 further comprising:
a first register that stores the identifier of the first threshold frequency at or below which gating can be enabled for the first plurality of flip-flop circuits; and
a second register that stores a second identifier of the second threshold frequency at or below which gating can be enabled for the second plurality of flip-flop circuits.
6. The system of claim 1 wherein the first of the clock signals for the first plurality of flip-flop circuits is the same as the second of the clock signals for the second plurality of flip-flop circuits.
7. The system of claim 1 further comprising:
a control module coupled to the first plurality of flip-flop circuits, the control module is configured to:
receive the first gating enable signal for the first plurality of flip-flop circuits from the gating control module,
receive, a clock enable signal and a global clock signal, and
enable gating of the global clock signal to provide the first of the clock signals for the first plurality of flip-flop circuits based on the first gating enable signal and the clock enable signal.
8. The system of claim 7 wherein
the first processor frequency is a frequency at which a clock enable signal is available at the control module for a first of the clock signals prior to a global clock signal becoming active at the control module, and
the second processor frequency is a frequency at which the clock enable signal is not available at the control module for the first of the clock signals prior to the global clock signal becoming active at the control module.
9. A system comprising:
a first plurality of flip-flop circuits;
a first frequency associated with the first plurality of flip-flop circuits, wherein the first frequency indicates a first threshold frequency above which a setup time requirement for the first plurality of flip-flop circuits is not met;
a second plurality of flip-flop circuits;
a second frequency associated with the second plurality of flip-flop circuits, wherein the second frequency indicates a second threshold frequency above which a setup time requirement for the second plurality of flip-flops is not met;
a first controller coupled to the first plurality of flip-flop circuits, wherein the first controller is configured to:
gate a global clock signal to provide a first clock signal to the first plurality of flip-flop circuits when a processing frequency for the system is below the first frequency, and
a second controller coupled to the second plurality of flip-flop circuits, wherein the second controller is configured to:
gate the global clock signal to provide a second clock signal to the second plurality of flip-flop circuits when the processing frequency for the system is below the second frequency; and
a gating control module coupled to the first controller and to the second controller, the gating control module configured to:
compare the processing frequency for the system to the first frequency at or below which gating can be enabled for the first plurality of flip-flop circuits,
set a first gating enable signal to the first controller based on whether the first frequency is greater than the processing frequency,
compare the processing frequency for the system to the second frequency at or below which gating can be enabled for the second plurality of flip-flop circuits, and
set a second gating enable signal to the second controller based on whether the second frequency is greater than the processing frequency.
10. The system of claim 9 further comprising:
a processor controller configured to generate a command to change the processing frequency for the system.
11. The system of claim 10 wherein the processor controller is further configured to:
transition to a lower processor frequency before the first controller determines whether to gate the first clock signal when the processing frequency is commanded to decrease.
12. The system of claim 10 wherein the processor controller is further configured to:
transition to a higher processor frequency after the first controller determines whether to gate the first clock signal when the processing frequency is commanded to increase.
13. The system of claim 9 wherein the first controller is further configured to:
receive the first gating enable signal from the gating control module,
receive a clock enable signal and the global clock signal, and
gate the global clock signal to provide the first clock signal based on the first gating enable signal and the clock enable signal.
14. A method of gating clock signals in a computer processing system comprising:
receiving a command to change a processor frequency for the processing system, wherein the processing system comprises
a first set of flip-flop circuits associated with a first identified frequency above which a setup time requirement for the first set of flip-flop circuits is not met, and
a second set of flip-flop circuits associated with a second identified frequency above which a setup time requirement for the second set of flip-flop circuits is not met;
determining whether to increase or decrease the processor frequency based on the command; and
when the processor frequency is commanded to decrease,
transitioning to a lower processor frequency,
comparing the lower processor frequency to the first identified frequency at or below which gating can be enabled for the first set of flip-flop circuits, and
generating a first gating enable signal for the first set of flip-flop circuits in response to the lower processor frequency being less than or equal to the first identified frequency, wherein the first gating enable signal controls gating of a first clock signal for the first set of flip-flop circuits.
15. The method of claim 14 further comprising:
when the processor frequency is commanded to increase to a higher processing frequency,
comparing the higher processing frequency to the first identified frequency at or below which gating can be enabled for the first set of flip-flop circuits,
not gating the clock signal in response to the higher processing frequency being greater than the first identified frequency for the first set of flip-flop circuits; and
transitioning to the higher processing frequency.
16. The method of claim 14 further comprising:
gating a global clock signal to provide the first clock signal based on the first gating enable signal and a first clock enable signal.
17. The method of claim 16 further comprising:
generating a second gating enable signal, wherein the second gating enable signal controls whether a second clock signal for a second set of flip-flop circuits will be gated; and
gating the global clock signal to provide the second clock signal to the second set of flip-flop circuits based on the second gating enable signal and a second clock enable signal.
18. The method of claim 16 further comprising:
providing the first clock enable signal as input to a gate with an output coupled to provide a second clock signal to the second set of flip-flop circuits.