Power management for peripheral component interconnect

1. An apparatus comprising:

an interface circuit configured to provide an interface with a peripheral component interconnect express (PCIe) link; and

a controller configured to:

monitor transmit traffic activity for the link;

monitor receive traffic activity for the link;

manage a first power of transmit lines of the link as a transmit group in accordance with the transmit traffic activity by converting the transmit traffic activity to a number of active differential line pairs of the transmit group using multiple thresholds and transitioning the link through an active state to a standby substate corresponding to the number of active differential line pairs of the transmit lines of the transmit group; and

manage a second power of receive lines of the link as a receive group in accordance with the receive traffic activity, independently of the power of the transmit lines by converting the receive traffic activity to a number of active differential line pairs of the receive group using multiple thresholds and transitioning the link through an active state to a standby substate corresponding to the number of active differential line pairs of the receive lines of the receive group.

2. The apparatus of claim 1 , wherein the controller is configured to set a transmit group link control register in accordance with the transmit traffic activity to store a number of active transmit lines and set a receive group link control register in accordance with the receive traffic activity to store a number of active receive lines.

3. The apparatus of claim 1 , wherein the controller is configured to set a transmit group capabilities register in accordance with the transmit traffic activity to store capabilities of the transmit lines and set a receive group capabilities register in accordance with the receive traffic activity to store capabilities of the receive lines.

4. The apparatus of claim 1 , wherein the standby state has at least one transmit line of the transmit group as an inactive line.

5. The apparatus of claim 4 , wherein the controller is configured to:

compare the transmit traffic activity of the link to a threshold; and

place the transmit lines into a standby substate in response to the transmit traffic activity being less than the threshold, wherein the standby substate is a lower power state than the active state.

6. The apparatus of claim 1 , wherein the controller is configured to manage the second power by placing a selected at least one receive line of the receive group into a standby state.

7. The apparatus of claim 6 , wherein the controller is further configured to:

compare the receive traffic activity of the link to a threshold; and

place the receive lines into a standby substate in response to the receive traffic activity being less than the threshold, wherein the standby substate is a lower power state than the active state.

8. The apparatus of claim 1 , wherein managing the first power comprises managing a number of active transmit lines for the transmit group of the link.

9. The apparatus of claim 1 , wherein the controller is configured to manage the first power by:

supplying one or more voltages or clocks to an interface circuit configured to provide an interface with the link; and

setting levels of the one or more voltages supplied to the interface circuit based on the first power.

10. A method comprising:

monitoring transmit traffic activity for a peripheral component interconnect express (PCIe) link;

monitoring receive traffic activity for the link;

managing a first power of transmit lines of the link as a transmit group in accordance with the transmit traffic activity by converting the transmit traffic activity to a number of active differential line pairs of the transmit group using multiple thresholds and transitioning the link through an active state to a standby substate corresponding to the number of active differential line pairs of the transmit lines of the transmit group; and

managing a second power of the receive lines of the link as a receive group in accordance with the receive traffic activity, independently of the power of the transmit lines by converting the receive traffic activity to a number of active differential line pairs of the receive group using multiple thresholds and transitioning the link through an active state to a standby substate corresponding to the number of active differential line pairs of the receive lines of the receive group.

11. The method of claim 10 , further comprising setting a transmit group link control register in accordance with the transmit traffic activity and setting a receive group link control register in accordance with the receive traffic activity.

12. The method of claim 10 , further comprising setting a transmit group link status register in accordance with the transmit traffic activity and setting a receive group link status register in accordance with the receive traffic activity.

13. The method of claim 10 , wherein the standby state has at least one transmit line of the transmit group as an inactive line.

14. The method of claim 13 , further comprising:

comparing the transmit traffic activity of the link to a threshold; and

placing the transmit lines into a standby substate in response to the transmit traffic activity being less than the threshold, wherein the standby substate is a lower power state than the active state.

15. The method of claim 10 , wherein the standby state has at least one receive line of the receive group as an inactive line.

16. The method of claim 15 , further comprising:

comparing the receive traffic activity of the link to a threshold; and

placing the receive lines into a standby substate in response to the receive traffic activity being less than the threshold, wherein the standby substate is a lower power state than the active state.

17. The method of claim 10 , wherein managing the second power comprises managing a number of active receive lines for the receive group of the link.

18. The method of claim 10 , wherein managing the second power comprises:

supplying one or more voltages or clocks to an interface circuit configured to provide an interface with the link; and

setting levels of the one or more voltages supplied to the interface circuit based on the second power.

19. A non-transitory computer-readable medium having instructions stored therein for causing a processor of an interconnect link to perform operations comprising:

monitoring transmit traffic activity for a peripheral component interconnect express (PCIe) link;

monitoring receive traffic activity for the link;

managing a first power of transmit lines of the link as a transmit group in accordance with the transmit traffic activity by converting the transmit traffic activity to a number of active differential line pairs of the transmit group using multiple thresholds and transitioning the link through an active state to a standby substate corresponding to the number of active differential line pairs of the transmit lines of the transmit group; and

managing a second power of the receive lines of the link as a receive group in accordance with the receive traffic activity, independently of the power of the transmit lines by converting the receive traffic activity to a number of active differential line pairs of the receive group using multiple thresholds and transitioning the link through an active state to a standby substate corresponding to the number of active differential line pairs of the receive lines of the receive group.

20. The non-transitory computer-readable medium of claim 19 , further comprising instructions for causing the processor of the interconnect link to perform operations comprising:

comparing the transmit traffic activity of the link to a threshold; and

placing a selected at least one transmit line of the transmit group into a standby state in response to the transmit traffic activity being less than the threshold, wherein the standby state is a lower power state.