Refresh scheme in a memory controller

• US 10,593,391 B2
• Filed: 07/18/2018
• Issued: 03/17/2020
• Est. Priority Date: 07/16/2018
• Status: Active Grant

• Current Assignee: Advanced Micro Devices, Inc.
• Original Assignee: Advanced Micro Devices, Inc.
• Inventors: Zhao, Liang, Yao, YuBin
• Primary Examiner(s): Tran, Michael T
• Application Number:
  US16/038,738
• Publication Number:
  US 20200020384A1
• Time in Patent Office: 608 Days
• Field of Search: 365222, 3652335
• CPC Class Codes: G06F 13/1642 with request queuing
• CPC Class Codes: G06F 13/18 based on priority control G06F13/1605 takes precedence
• CPC Class Codes: G11C 11/40603 Arbitration, priority and concurrent access to memory cells for read/write or refresh operations
• CPC Class Codes: G11C 11/40611 External triggering or timing of internal or partially internal refresh operations, e.g. auto-refresh or CAS-before-RAS triggered refresh
• CPC Class Codes: G11C 11/40615 Internal triggering or timing of refresh, e.g. hidden refresh, self refresh, pseudo-SRAMs
• CPC Class Codes: G11C 11/40618 Refresh operations over multiple banks or interleaving
• CPC Class Codes: G11C 11/4076 Timing circuits for regeneration management G11C11/406

Abstract

In one form, a memory controller includes a command queue, an arbiter, a refresh logic circuit, and a final arbiter. The command queue receives and stores memory access requests for a memory. The arbiter selectively picks accesses from the command queue according to a first type of accesses and a second type of accesses. The first type of accesses and the second type of accesses correspond to different page statuses of corresponding memory accesses in the memory. The refresh logic circuit generates a refresh command to a bank of the memory and provides a priority indicator with the refresh command whose value is set according to a number of pending refreshes. The final arbiter selectively orders the refresh command with respect to memory access requests of the first type accesses and the second type accesses based on the priority indicator.

Claims

1. A memory controller, comprising:

a command queue for receiving and storing memory access requests for a memory;

an arbiter for selectively picking accesses from the command queue according to a first type of accesses and a second type of accesses, wherein the first type of accesses and the second type of accesses correspond to different page statuses of corresponding memory accesses in the memory;

a refresh logic circuit for generating a refresh command to a bank of the memory, and providing a priority indicator with the refresh command whose value is set according to a number of pending refreshes, wherein the refresh logic circuit assigns the priority indicator one of a first priority status and a second priority status; and

a final arbiter for selectively ordering the refresh command with respect to memory access requests of the first type accesses and the second type accesses based on the priority indicator, wherein the final arbiter elevates the refresh command between the first type of accesses and the second type of accesses in response to the first priority status.

2. The memory controller of claim 1, wherein the final arbiter further elevates the refresh command above the first type of accesses and the second type of accesses in response to the second priority status.

3. The memory controller of claim 1, wherein the refresh logic circuit comprises:

a refresh counter that counts a number of pending per bank refreshes; and

a comparator coupled to the refresh counter that provides the first priority status to the refresh command if the refresh counter exceeds a predetermined threshold.

4. The memory controller of claim 3, wherein, based on a periodic period of time, the refresh logic circuit further elevates the priority indicator for a pending refresh command when the refresh counter is between a lower threshold and an upper threshold.

5. The memory controller of claim 4, wherein the periodic period of time is a derivative of a predetermined refresh interval and a total number of banks assigned to the memory controller.

6. The memory controller of claim 1, wherein the refresh logic circuit further assigns the priority indicator based on a programmable counter, and the programmable counter tracks a number of pending refresh commands.

7. The memory controller of claim 6, wherein the refresh logic circuit further elevates the priority indicator for a pending refresh command when the programmable counter is above an urgent refresh count threshold.

8. The memory controller of claim 1, wherein the first type accesses is not a page hit and the second type accesses is a page hit.

9. The memory controller of claim 1, wherein the arbiter comprises a plurality of sub-arbiters for selectively picking accesses based on sub-arbitrations, wherein one sub-arbitration is a page hit and each other sub-arbitration is not a page hit.

10. The memory controller of claim 1, wherein in response to simultaneously receiving a priority indicator for more than one bank, the final arbiter relegates the priority indicator of the bank of the memory that is a most recent recipient of the refresh command below the bank of the memory that is a least recent recipient of the refresh command.

11. The memory controller of claim 1, wherein the memory controller is adapted to interface to synchronous graphics random access memory capable of supporting per two-bank refresh.

12. The memory controller of claim 11, wherein the refresh logic circuit further elevates a priority indicator for a pending refresh command for a paired bank when the priority indicator is a first priority status and a refresh timer is above a refresh timing interval.

13. The memory controller of claim 12, wherein the refresh logic circuit further elevates the priority indicator for a pending refresh command to a second priority status for the paired bank when a programmable counter is above an urgent refresh count threshold and both banks of the paired bank have a first type access.

14. A data processing system, comprising:

a memory accessing agent for providing memory access requests for a memory;

a memory system coupled to the memory accessing agent; and

a memory controller coupled to the memory system and the memory accessing agent, the memory controller comprising;

a command queue for storing memory access commands received from the memory accessing agent;

an arbiter for selectively picking memory accesses from the command queue according to a first type of access and a second type of access, wherein each type of access corresponds to a different page status of a bank in the memory; and

a final arbiter that arbitrates based on input received from a refresh logic circuit that generates a refresh command to the bank of the memory and provides a priority indicator with the refresh command, whose value is set according to a number of pending refreshes, to selectively order the refresh command with respect to a first type of access and a second type of access,

wherein the memory controller assigns the priority indicator one of a first priority status and a second priority status, and elevates the refresh command between the first type of access and the second type of access in response to the first priority status.

15. The data processing system of claim 14, wherein:

the memory controller further assigns the priority indicator the first priority status based, in part, on a clock;

the clock is for tracking a refresh interval; and

the memory controller determines an intermediate refresh time interval based on a refresh time interval and a total number of banks assigned to the memory controller.

16. The data processing system of claim 15, wherein the intermediate refresh time interval is a period of time that is less than the refresh time interval.

17. The data processing system of claim 15, wherein in response to the intermediate refresh time interval, the memory controller generates the refresh command to the bank at a higher frequency than the refresh interval.

18. The data processing system of claim 14, wherein the memory controller further:

assigns the priority indicator based on a predetermined threshold of a refresh counter, wherein the refresh counter counts a number of pending per bank refreshes in the memory; and

elevates the priority indicator for a pending refresh command, based on a periodic time cycle, when the refresh counter is between a lower threshold and an upper threshold.

19. The data processing system of claim 14, wherein the memory controller further assigns the priority indicator a second priority status based on a programmable counter.

20. The data processing system of claim 19, wherein the memory controller elevates the priority indicator of the refresh command above the first type of access and the second type of access in response to the second priority status.

21. The data processing system of claim 19, wherein the memory controller blocks a corresponding bank of memory from opening in response to assertion of the second priority status.

22. The data processing system of claim 14, wherein the arbiter comprises a plurality of sub-arbiters, and the plurality of sub-arbiters are for selectively picking accesses based on sub-arbitrations, wherein one sub-arbitration is a page hit and each other sub-arbitration is not a page hit.

23. The data processing system of claim 14, wherein the memory accessing agent comprises:

a central processing unit core;

a graphics processing unit core; and

a data fabric for interconnecting the central processing unit core and the graphics processing unit core to the memory controller.

24. The data processing system of claim 14, wherein the memory is a high bandwidth memory.

25. A method for managing refresh of a memory in a memory system via a memory controller, the method comprising:

receiving a plurality of memory access requests;

storing the plurality of memory access requests in a command queue; and

selectively picking memory accesses requests from the command queue according to a first type of accesses and a second type of accesses that correspond to different page statuses of corresponding memory accesses in the memory;

generating a refresh command to a bank of the memory, and providing a priority indicator with the refresh command whose value is set according to a number of pending refreshes, wherein providing the priority indicator to the refresh command further comprises assigning the priority indicator one of a first priority status and a second priority status, and elevating the refresh command between the first type accesses and the second type accesses in response to the first priority status; and

selectively ordering the refresh command with respect to memory access requests of the first type of accesses and the second type of accesses based on the priority indicator.

26. The method of claim 25, wherein providing the priority indicator to the refresh command further comprises:

elevating the refresh command above the first type accesses and the second type of accesses in response to the second priority status.

27. The method of claim 25, further comprising assigning the priority indicator based on a predetermined threshold of a refresh counter, wherein the refresh counter counts a number of pending per bank refreshes in the memory.

28. The method of claim 27, further comprising elevating the priority indicator for a pending refresh command, based on a periodic period of time, when the refresh counter is between a lower threshold and an upper threshold.

29. The method of claim 28, wherein the periodic period of time is a derivative of a predetermined refresh interval and a total number of banks assigned to the memory controller.

30. The method of claim 25, further comprising assigning the priority indicator based on a programmable counter, and the programmable counter tracks a number of refresh commands that are scheduled and incomplete.

31. The method of claim 30, further comprising elevating the priority indicator for a pending refresh command when the programmable counter is above an urgent refresh count threshold.

32. The method of claim 25, wherein the first type accesses is not a page hit and the second type of accesses is a page hit.

33. The method of claim 25, further comprising selectively picking accesses based on sub-arbitrations, wherein an arbiter comprises a plurality of sub-arbiters and one sub-arbitration is a page hit and each other sub-arbitration is not a page hit.

34. The method of claim 25, wherein the refresh command is for a selected bank.