Cache dormant indication

Patent metadata

Field	Value
Publication number	US-2016259729-A1
Application number	US-201615040440-A
Country	US
Kind code	A1
Filing date	Feb 10, 2016
Priority date	Mar 2, 2015
Publication date	Sep 8, 2016
Grant date	—

Abstract

A data processing apparatus includes a first agent which generates a cache dormant indication when a cache is in a dormant state, and a second agent which issues cache maintenance requests for data stored in the cache accessed by the first agent. in response to the cache dormant indication generated by the first agent, the second agent may suppress issuing of cache maintenance requests for the cache accessed by the first agent.

First claim

I claim:

1 . A data processing apparatus comprising:
a first agent configured to generate a cache dormant indication when a cache is in a dormant state: and a second agent configured to issue cache maintenance requests for data stored in the cache, wherein in response to the cache dormant indication generated by the first agent, the second agent is configured to supress issuing of at least some cache maintenance requests for the cache.

2 . The apparatus according to claim 1 , wherein the cache is in the dormant state when the cache stores no valid data.

3 . The apparatus according to claim 1 , wherein the cache is in the dormant state when the cache stores no valid data and there are no outstanding transactions for updating the cache.

4 . The apparatus according to claim 1 , wherein the cache is in the dormant state when the cache stores no dirty data.

5 . The apparatus according to claim 1 , wherein the cache is in the dormant state when the cache stores no valid data relevant to the second agent.

6 . The apparatus according to claim 1 , wherein the cache is in the dormant state when the cache stores no valid data of at least one predetermined category.

7 . The apparatus according to claim 1 , wherein the cache is in the dormant state when the cache is in a power saving state.

8 . The apparatus according to claim 1 , wherein the first agent is configured to generate the cache dormant indication by setting a cache dormant flag in a storage location accessible to the second agent.

9 . The apparatus according to claim 1 , wherein the first agent is configured to generate the cache dormant indication by asserting a hardware signal transmitted to the second agent.

10 . The apparatus according to claim 1 , wherein the first agent is configured to generate the cache dormant indication by transmitting at least one message to the second agent.

11 . The apparatus according to claim 1 , wherein the cache maintenance requests comprise one or more of:
snoop requests to query whether data is stored in the cache or to query a coherency status of data stored in the cache; clean requests to trigger write back of dirty data from the cache to memory; and invalidate requests to invalidate data stored in the cache.

12 . The apparatus according to claim 1 , wherein in response to the cache dormant indication, the first agent is configured to suppress issuing of at least one predetermined type of cache maintenance request.

13 . The apparatus according to claim 1 , wherein the first agent and the second agent comprise the same processing device.

14 . The apparatus according to claim 1 , wherein the first agent comprises a graphics processing unit.

15 . The apparatus according to claim 1 , wherein the cache comprises a data cache configured to store data to be processed.

16 . The apparatus according to claim 1 , wherein the cache comprises an address translation cache configured to store address translation data for translating addresses.

17 . A first agent device comprising:
control circuitry configured to determine whether a cache is in a dormant state, and when the cache is in the dormant state, to generate a cache dormant indication accessible to a second agent device, wherein the second agent device is for issuing cache maintenance requests for data stored in the cache.

18 . A second agent device comprising:
control circuitry configured to issue cache maintenance requests for data stored in a cache, wherein in response to a cache dormant indication generated by a first agent device indicating that the cache is in a dormant state, the control circuitry is configured to supress issuing of at least some cache maintenance requests for said cache.

19 . A data processing method comprising;
a first agent generating a cache dormant indication when a cache is in a dormant state; and in response to the cache dormant indication generated by the first agent, a second agent suppressing issuing of at least some cache maintenance requests for maintaining coherency of data stored in the cache.

20 . A data processing method comprising;
a first agent determining whether a cache is in a dormant state; and when the cache is in the dormant state, generating a cache dormant indication which is accessible to a second agent, wherein the second agent device is for issuing cache maintenance requests for data stored in the cache.

21 . A data processing method comprising;
determining whether a first agent has generated a cache dormant indication indicating whether a cache is in a dormant state; and when the first agent has generated the cache dormant indication, suppressing issuing of at least some cache maintenance requests for data stored in the cache.

22 . A storage medium storing a computer program which when executed by a processing unit controls the processing unit to perform the method of claim 1 .

Assignees

• Advanced Risc Mach Ltd

Inventors

• Persson Håkan

Classifications

• G06F12/0831

  using a bus scheme, e.g. with bus monitoring or watching means · CPC title

• G06F1/3225

  of memory devices · CPC title

• G06F2212/1041

  Resource optimization · CPC title

• G06F12/0844 Primary

  Multiple simultaneous or quasi-simultaneous cache accessing · CPC title

• G06F1/3275 Primary

  Power saving in memory, e.g. RAM, cache · CPC title