Arbitrated Access To Resources Among Multiple Devices

Patent metadata

Field	Value
Publication number	US-2016140071-A1
Application number	US-201414540436-A
Country	US
Kind code	A1
Filing date	Nov 13, 2014
Priority date	Nov 13, 2014
Publication date	May 19, 2016
Grant date	—

Abstract

An arbiter circuit manages and enforces arbitration and quality of service (QOS) among multiple devices accessing a resource, such as a memory. The arbiter circuit receives requests from a number of devices to use resources of a bridge connecting to a memory, and maintains a count of bridge resources available on a per-device and per-bus basis. The arbiter circuit operates to select a next one of the requests to grant a bridge resource based on the device originating the request, a count of the per-device resources available, and a count of the resources available to the bus connecting the device to the bridge.

First claim

What is claimed is:

1 . A circuit comprising:
a device interface for receiving requests from a plurality of devices to access a memory via a bridge, each of the requests including a device identifier; a per-device counter configured to maintain a resource count allocated to each device; a bus counter configured to maintain a resource count for forwarding the requests to the bridge via a bus; and an arbiter circuit configured to select a next one of the plurality of requests to forward to the bridge based on 1) the device identifier of the request, 2) a count of the per-device counter corresponding to the device identifier, and 3) a count of the bus counter.

2 . The circuit of claim 1 , wherein the per-device counter is further configured to limit a maximum resource count to a first of the plurality of devices relative to a second of the plurality of devices.

3 . The circuit of claim 1 , wherein the arbiter circuit is further configured to suspend requests having a given device identifier in response to detecting that the per-device counter for the given device identifier indicates a count that is less than a threshold value.

4 . The circuit of claim 1 , wherein the arbiter circuit is further configured to suspend requests in response to detecting that the bus counter indicates a count that is less than a threshold value.

5 . The circuit of claim 1 , wherein the arbiter circuit is further configured to suspend one of the plurality requests based on a) an indication of a resource count required by the request, and b) a predetermined threshold for per-request resources.

6 . The circuit of claim 1 , further comprising a plurality of buffers each configured to store the requests received from a respective device at the device interface.

7 . The circuit of claim 6 , wherein each of the plurality of buffers generates a backpressure command in response to reaching a threshold storage value.

8 . The circuit of claim 1 , wherein the per-device counter is further configured to increment in response to receiving an indication that an additional resource associated with a given device identifier is available.

9 . The circuit of claim 1 , wherein the bus counter is further configured to increment in response to receiving an indication that an additional resource associated with the circuit is available.

10 . The circuit of claim 1 , further comprising a bridge control circuit, the bridge control circuit configured to control a count of the bus counter.

11 . The circuit of claim 10 , wherein the bridge control circuit is further configured to prevent return of an initial given count of resources to the bus counter.

12 . A method comprising:
receiving requests from a plurality of devices to access a memory, each of the requests including a device identifier; maintaining a per-device resource count allocated to each device; maintaining a bus resource count for forwarding the requests to the bridge via a bus; and selecting a next one of the plurality of requests to forward to the bridge based on a) the device identifier of the request, b) the per-device resource count corresponding to the device identifier, and c) the bus resource count.

13 . The method of claim 12 , further comprising limiting, via the per-device resource count, a maximum resource count to a first of the plurality of devices relative to a second of the plurality of devices.

14 . The method of claim 12 , further comprising suspending requests having a given device identifier in response to detecting that the per-device count for the given device identifier indicates a count that is less than a threshold value.

15 . The method of claim 12 , further comprising suspending requests in response to detecting that the bus counter indicates a count that is less than a threshold value.

16 . The method of claim 12 , further comprising suspend one of the plurality requests based on a) an indication of a resource count required by the request, and b) a predetermined threshold for per-request resources.

17 . The method of claim 12 , further comprising storing the requests received from a respective device at a device interface.

18 . The method of claim 17 , further comprising generating a backpressure command in response to reaching a threshold storage value.

19 . The method of claim 12 , further comprising incrementing the per-device resource count in response to receiving an indication that an additional resource associated with a given device identifier is available.

20 . The method of claim 12 , further comprising incrementing the bus resource count in response to receiving an indication that an additional resource associated with the circuit is available.

21 . The method of claim 12 , further comprising controlling a count of the bus counter via a signal from the bridge.

22 . The method of claim 21 , further comprising preventing return of an initial given count of resources to the bus counter.

Assignees

• Cavium Inc

Inventors

• Sanzone Robert A
• Snyder Ii Wilson P
• Kessler Richard E

Classifications

• G06F13/364

  using independent requests or grants, e.g. using separated request and grant lines · CPC title

• G06F13/362

  with centralised access control · CPC title

• G06F13/4031 Primary

  with arbitration · CPC title

• G06F13/1642

  with request queuing · CPC title