Techniques for entering a low-power link state
First Claim
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1. An apparatus comprising:
- a physical point-to-point link within an electronic system having a cache-coherent, link-based interconnect fabric;
a first component within the electronic system coupled with a first end of the point-to-point link, the first component to transmit a request over the point-to-point link to initiate transition of the point-to-point link from an active state to a low power state, the first component to operate as a master device in a power control negotiation, wherein the point-to-point link is to be incapable of transmitting packets during the low power state; and
a second component within the electronic system coupled with a second end of the point-to-point link, the second component, in response to the request, to selectively allow or disallow the transition of the point-to-point link from the active state to the low power state, wherein the second component sends negative acknowledge (NACK) message to disallow the transition of the point-to-point link from the active state to the low power state, and further wherein the first component maintains the point-to-point link in the active state in response to the NACK message, the second component to operate as a slave device in the power control negotiation, wherein no pending transactions or subsequent transactions are to occur within an upcoming period of time.
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Abstract
Techniques to cause a point-to-point link between system components to engage in a negotiation process that may lead to the link transitioning from an active state in which data may be transmitted between system components to a low power state where data may not be transmitted. The negotiation process may occur between each pair of nodes within an electronic system that are interconnected via point-to-point link. The negotiation may ensure that there are no pending transactions or transactions that may occur within an upcoming period of time. Through this negotiation each component acknowledges and agrees to transition the link to the low power state.
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Citations
20 Claims
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1. An apparatus comprising:
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a physical point-to-point link within an electronic system having a cache-coherent, link-based interconnect fabric; a first component within the electronic system coupled with a first end of the point-to-point link, the first component to transmit a request over the point-to-point link to initiate transition of the point-to-point link from an active state to a low power state, the first component to operate as a master device in a power control negotiation, wherein the point-to-point link is to be incapable of transmitting packets during the low power state; and a second component within the electronic system coupled with a second end of the point-to-point link, the second component, in response to the request, to selectively allow or disallow the transition of the point-to-point link from the active state to the low power state, wherein the second component sends negative acknowledge (NACK) message to disallow the transition of the point-to-point link from the active state to the low power state, and further wherein the first component maintains the point-to-point link in the active state in response to the NACK message, the second component to operate as a slave device in the power control negotiation, wherein no pending transactions or subsequent transactions are to occur within an upcoming period of time. - View Dependent Claims (2, 3, 4, 5)
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6. A system comprising:
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a physical point-to-point link within an electronic system having a cache-coherent, link-based interconnect fabric; a first component within the electronic system coupled with a first end of the point-to-point link, the first component to transmit a request over the point-to-point link to initiate transition of the point-to-point link from an active state to a low power state, the first component to operate as a master device in a power control negotiation, wherein the link is to be incapable of transmitting packets during the low power state; a second component within the electronic system coupled with a second end of the point-to-point link, the second component, in response to the request, to selectively allow or disallow the transition of the point-to-point link from the active state to the low power state, wherein the second component sends negative acknowledge (NACK) message to disallow the transition of the point-to-point link from the active state to the low power state, and further wherein the first component maintains the point-to-point link in the active state in response to the NACK message, the second component to operate as a slave device in the power control negotiation, wherein no pending transactions or subsequent transactions are to occur within an upcoming period of time; and a dynamic random access memory coupled with the second component. - View Dependent Claims (7, 8, 9, 10)
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11. A method comprising:
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transmitting a request message from a master component of an electronic system to a slave component of the electronic system having a cache-coherent, link-based interconnect fabric over a physical point-to-point link, the request to initiate transition of the point-to-point link from an active state to a low power state; receiving a response message from the slave component with the master component, the response message being either an acknowledge (ACK) message to allow transition from the active state to the low power state or a negative acknowledge (NACK) message to disallow transition from the active state to the low power state, the master component and the slave component to negotiate power level changes, where the negotiation is to ensure that no pending transactions or subsequent transactions occur within an upcoming period of time; and causing the point-to-point link to transition to the low power state in response to receiving the ACK message from the slave device, wherein no packets are to be transmitted over the point-to-point link during the low power state. - View Dependent Claims (12, 13, 14, 15)
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16. A method comprising:
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receiving, with a slave component within an electronic system, a request message from a master component within the electronic system having a cache-coherent, link-based interconnect fabric over a point-to-point link, the request to initiate transition of the point-to-point link from an active state to a low power state, wherein no packets are to be transmitted over the point-to-point link during the low power state; determining whether to respond to the request message with an acknowledge (ACK) message to allow transition from the active state to the low power state or to respond to the request with a negative acknowledge (NACK) message to disallow transition from the active state to the low power state, the master component and the slave component to negotiate power level changes, where the negotiation is to ensure that no pending transactions or subsequent transactions occur within an upcoming period of time; and transmitting either the ACK message or the NACK message to the master component over the point-to-point link. - View Dependent Claims (17, 18, 19, 20)
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Specification