Method, apparatus, and system for improving resume times for root ports and root port integrated endpoints

Abstract

A device is determined to be in a low power state. A transition from the low power state to an active state is initiated, where a fixed minimum recovery time is defined for transitions from the low power state to the active state. A capability of the device is identified corresponding to transition of the device from the low power state to the active state, and the transition of the device from the low power state to the active state is completed based at least in part on the capability, such that the transition is to be completed prior to expiration of the fixed minimum recovery time.

What is claimed is: 
     
         1 . An apparatus comprising:
 recovery logic to:
 determine that a device is in a low power state; 
 initiate a transition of the device from the low power state to an active state, wherein a fixed minimum recovery time is defined for transitions from the low power state to the active state; 
 identify a capability of the device corresponding to transition of the device from the low power state to the active state; and 
 complete transition of the device from the low power state to the active state based at least in part on the capability, wherein the transition is to be completed prior to expiration of the fixed minimum recovery time. 
   
     
     
         2 . The apparatus of  claim 1 , wherein the capability comprises an interrupt capability and the recovery logic is further to receive an interrupt from the device, where the interrupt is an indication that the device is ready to complete the transition. 
     
     
         3 . The apparatus of  claim 2 , wherein the recovery logic is further to monitor the device for the interrupt. 
     
     
         4 . The apparatus of  claim 3 , wherein the recovery logic is to complete the transition according to a defined recovery time for the device if the interrupt is not received prior to the defined recovery time. 
     
     
         5 . The apparatus of  claim 4 , wherein the defined recovery time comprises the fixed minimum recovery time. 
     
     
         6 . The apparatus of  claim 4 , wherein the defined recovery time comprises an advertised recovery time specific to the device. 
     
     
         7 . The apparatus of  claim 1 , wherein the capability comprises an advertised recovery time for the device, and the advertised recovery time is shorter than the fixed minimum recovery time. 
     
     
         8 . The apparatus of  claim 7 , wherein the recovery logic is further to apply the advertised recovery time to the transition of the device from the low power state to the active state instead of the fixed minimum recovery time. 
     
     
         9 . The apparatus of  claim 8 , wherein the recovery logic is further to apply the fixed minimum recovery time to another device in a transition of the other device from the low power state to the active state. 
     
     
         10 . The apparatus of  claim 1 , wherein the device comprises a Peripheral Component Interconnect Express (PCIe)-compliant device. 
     
     
         11 . The apparatus of  claim 10 , wherein the low power state comprises a D3 state and the active state comprises a D0 state. 
     
     
         12 . The apparatus of  claim 1 , wherein completing the transition of the device from the low power state to the active state is to include sending of a configuration access request to the device. 
     
     
         13 . The apparatus of  claim 1 , wherein the device comprises at least one of a root port, downstream port, or a root complex integrated end point. 
     
     
         14 . An apparatus comprising:
 machine readable memory storing a power management capability structure defining power management capabilities of at least one device; and   a power management controller to:
 identify a particular capability for the device from the power management capability structure; 
 complete transition of the device from a low power state to an active state based at least in part on the particular capability, wherein the transition is to be completed prior to expiration of a fixed minimum recovery time defined for transitions from the low power state to the active state. 
   
     
     
         15 . The apparatus of  claim 14 , wherein the power management capability structure defines for the device, whether an alternate recovery time is advertised for the device. 
     
     
         16 . The apparatus of  claim 15 , wherein the power management capability structure defines an alternate recovery time for the device that is shorter than the fixed minimum recovery time. 
     
     
         17 . The apparatus of  claim 16 , wherein the power management controller is to apply the alternate recovery time to complete the transition of the device from the low power state to the active state. 
     
     
         18 . The apparatus of  claim 15 , wherein the power management controller is to apply the fixed minimum recovery time if an alternate recovery time is not advertised. 
     
     
         19 . The apparatus of  claim 14 , wherein the power management capability structure defines for the device, whether an interrupt is supported by the device, wherein the power management controller is to complete transition of the device from the low power state to the active state based on receipt of the interrupt from the device. 
     
     
         20 . The apparatus of  claim 19 , wherein the power management controller is to monitor the device for the interrupt if the power management capability structure indicates that the device supports the interrupt. 
     
     
         21 . A method comprising:
 determining that a device is in a low power state;   initiating a transition of the device from the low power state to an active state, wherein a fixed minimum recovery time is defined for transitions from the low power state to the active state;   identifying a capability of the device corresponding to transition of the device from the low power state to the active state; and   completing transition of the device from the low power state to the active state based at least in part on the capability, wherein the transition is to be completed prior to expiration of the fixed minimum recovery time.   
     
     
         22 . The method of  claim 21 , wherein the capability comprises an interrupt capability and the recovery logic is further to receive an interrupt from the device, where the interrupt is an indication that the device is ready to complete the transition. 
     
     
         23 . The method of  claim 21 , wherein the capability comprises an advertised recovery time for the device, and the advertised recovery time is shorter than the fixed minimum recovery time. 
     
     
         24 . The method of  claim 21 , wherein initiating the transition of the device from the low power state to the active state includes providing power to the device. 
     
     
         25 . A system comprising:
 a device; and   a power management controller communicatively coupled to the device, the power management controller to:
 determine that the device is in a low power state; 
 initiate a transition of the device from the low power state to an active state, wherein a fixed minimum recovery time is defined for transitions from the low power state to the active state; 
 identify a capability of the device corresponding to transition of the device from the low power state to the active state; and 
 complete transition of the device from the low power state to the active state based at least in part on the capability, wherein the transition is to be completed prior to expiration of the fixed minimum recovery time. 
   
     
     
         26 . The system of  claim 25 , wherein the device comprises a root port. 
     
     
         27 . The system of  claim 25 , wherein the device comprises a root complex integrated end point.