Power mangement techniques for an input/output (I/O) subsystem

Abstract

A method and system to improve the power management for an I/O subsystem. In one embodiment of the invention, the power management of an upstream port of the I/O subsystem is improved by increasing the upstream link utilization when the upstream port is an active power state and by increasing or prolonging the power saving period of the upstream port when the upstream port is in a low power state.

What is claimed is:  
     
       1. An apparatus comprising:
 an upstream port to couple to a tunnel control interface communication link, a tunnel access request interface communication link and a communication link, the communication link, the tunnel control interface communication link and the tunnel access request interface communication link each a separate communication link, the upstream port to:
 send a first indication to a downstream port via the tunnel control interface communication link to indicate whether the upstream port is accepting data; and 
 enter a low power state in response to the first indication that the upstream port is not accepting data, wherein the first indication comprises a voltage of a first logic level; and 
 
 the downstream port coupled to the upstream port via the tunnel control interface communication link, the tunnel access request interface communication link and the communication link, the downstream port to:
 store one or more received data packets in response to receipt of the first indication that the upstream port is not accepting data; 
 compare the stored one or more received data packets with a threshold; and 
 
 send a second indication to the upstream port, via a tunnel access request communicated on the tunnel access request interface communication link, whether the downstream port is ready to send the stored one or more received data packets based on the comparison of the stored one or more received data packets with the threshold, wherein the second indication comprises a voltage of a second logic level to indicate that the downstream port is ready to send the stored one or more received data packets. 
 
     
     
       2. The apparatus of  claim 1 , wherein the threshold comprises one of a time-based threshold, a level-based threshold, and a percentage of unused buffer space in the downstream port. 
     
     
       3. The apparatus of  claim 1 , wherein the upstream port is further to:
 enter an active power state in response to receipt of the second indication from the downstream port that the downstream port is ready to send the stored one or more received data packets; 
 notify the downstream port that the upstream port is accepting data; and 
 receive the stored one or more received data packets in response to entering the active power state. 
 
     
     
       4. The apparatus of  claim 1 , wherein the second indication comprises a request for permission to send the stored one or more received data packets. 
     
     
       5. The apparatus of  claim 1 , wherein the tunnel access request interface communication link comprises a second communication link coupled to the upstream port and the downstream port to enable communication of the tunnel access request. 
     
     
       6. The apparatus of  claim 5 , wherein the tunnel control interface communication link comprises a third communication link coupled to the upstream port and the downstream port to enable communication of the first indication from the upstream port, wherein the first indication comprises a tunnel close signal. 
     
     
       7. An apparatus comprising:
 a downstream port to couple to a tunnel control interface communication link, a tunnel access request interface communication link and a communication link, the communication link, the tunnel control interface communication link and the tunnel access request interface communication link each a separate communication link, the downstream port to:
 store one or more received data packets in response to receiving a first indication that an upstream port is not accepting data, the first indication comprising a voltage of a first logic level; 
 compare the one or more stored data packets with a first threshold; and 
 send a second indication, via a tunnel access request communicated on the tunnel access request interface communication link, whether the downstream port is ready to send the one or more stored data packets based on the comparison of the one or more stored data packets with the first threshold, wherein the second indication comprises a voltage of a second logic level to indicate that the downstream port is ready to send the one or more stored data packets; and 
 
 the upstream port coupled to the downstream port via the tunnel control interface communication link, the tunnel access request interface communication link and the communication link, the upstream port to:
 facilitate the first indication via the tunnel control interface communication link to the downstream port whether the upstream port is to accept data based on a second threshold; and 
 enter a low power state in response to the first indication that the upstream port is not accepting data. 
 
 
     
     
       8. The apparatus of  claim 7 , wherein the first threshold and the second threshold each comprises one of a time-based threshold, a level-based threshold, and a percentage of unused buffer space in the downstream port. 
     
     
       9. The apparatus of  claim 7 , wherein the upstream port is further to:
 enter an active power state in response to receipt of the second indication that the downstream port is ready to send the stored one or more received data packets; and 
 receive the stored one or more received data packets in response to entering the active power state. 
 
     
     
       10. The apparatus of  claim 7 , wherein the downstream port is further to:
 send the stored one or more received data packets in response to receipt of the first indication from the upstream port that the upstream port is accepting data. 
 
     
     
       11. The apparatus of  claim 7 , wherein the apparatus is compliant at least in part with a Peripheral Component Interface Express (PCIe) standard. 
     
     
       12. The apparatus of  claim 7 , wherein the second indication indication comprises a request for permission to send the stored one or more data packets. 
     
     
       13. A method comprising:
 storing, by a downstream port, one or more received data packets in response to receiving a first indication that an upstream port coupled to the downstream port via a tunnel control interface communication link, a tunnel access request interface communication link, and a communication link is not accepting data, the communication link, the tunnel control interface communication link and the tunnel access request interface communication link each a separate communication link, the first indication comprising a voltage of a first logic level; 
 comparing, by the downstream port, the one or more stored data packets with a threshold; and 
 sending a second indication, by the downstream port, via a tunnel access request communicated on the tunnel access request interface communication link, whether the downstream port is ready to send the one or more stored data packets based on the comparison of the one or more stored data packets with the threshold, wherein the second indication comprises a voltage of a second logic level to indicate that the downstream port is ready to send the one or more stored data packets. 
 
     
     
       14. The method of  claim 13 , wherein the threshold is a first threshold, the method further comprising:
 facilitating, by the upstream port, the first indication whether the upstream port is accepting data based on a second threshold; and 
 entering, by the upstream port, a low power state in response to the first indication that the upstream port is not accepting data. 
 
     
     
       15. The method of  claim 14 , wherein the first threshold and the second threshold each comprises one of a time-based threshold, a level-based threshold, and a percentage of unused buffer space in the downstream port. 
     
     
       16. The method of  claim 14 , further comprising:
 entering, by the upstream port, an active power state in response to receiving the second indication that the downstream port is ready to send the stored one or more received data packets; and 
 receiving, by the upstream port, the stored one or more received data packets in response to entering the active power state. 
 
     
     
       17. The method of  claim 14 , further comprising:
 sending, by the downstream port, the stored one or more received data packets in response to receiving the first indication from the upstream port that the upstream port is accepting data based on the second threshold. 
 
     
     
       18. The method of  claim 13 , wherein the downstream port and the upstream port are each compliant at least in part with a Peripheral Component Interface Express (PCIe) standard.