TILE-BASED GRAPHICS

• US 20140292782A1
• Filed: 03/18/2014
• Published: 10/02/2014
• Est. Priority Date: 04/02/2013
• Status: Active Grant

• Current Assignee: Imagination Technologies Limited (Imagination Technologies Group Ltd.)
• Original Assignee: Imagination Technologies Limited (Imagination Technologies Group Ltd.)
• Inventors: FISHWICK, Steven John, HOWSON, John
• Granted Patent: US 9,928,563 B2
• Time in Patent Office: Days
• US Class Current: 345/522
• CPC Class Codes: G06F 12/0811 with multilevel cache hierarchies
• CPC Class Codes: G06F 12/0815 Cache consistency protocols
• CPC Class Codes: G06F 12/0875 with dedicated cache, e.g. instruction or stack
• CPC Class Codes: G06F 12/0891 using clearing, invalidating or resetting means
• CPC Class Codes: G06F 12/12 Replacement control
• CPC Class Codes: G06F 12/126 with special data handling, e.g. priority of data or instructions, handling errors or pinning
• CPC Class Codes: G06F 2212/1021 Hit rate improvement
• CPC Class Codes: G06F 2212/302 In image processor or graphics adapter
• CPC Class Codes: G06F 2212/45 Caching of specific data in cache memory
• CPC Class Codes: G06F 2212/70 Details relating to dynamic memory management
• CPC Class Codes: G06T 1/20 Processor architectures; Processor configuration, e.g. pipelining
• CPC Class Codes: G06T 1/60 Memory management
• CPC Class Codes: G06T 15/00 3D [Three Dimensional] image rendering
• CPC Class Codes: G06T 15/005 General purpose rendering architectures

Abstract

A tile-based graphics system has a rendering space sub-divided into a plurality of tiles which are to be processed. Graphics data items, such as parameters or texels, are fetched into a cache for use in processing one of the tiles. Indicators are determined for the graphics data items, whereby the indicator for a graphics data item indicates the number of tiles with which that graphics data item is associated. The graphics data items are evicted from the cache in accordance with the indicators of the graphics data items. For example, the indicator for a graphics data item may be a count of the number of tiles with which that graphics data item is associated, whereby the graphics data item(s) with the lowest count(s) is (are) evicted from the cache.

Claims

1. A method of processing data in a tile-based graphics system having a rendering space sub-divided into a plurality of tiles with which graphics data items are associated, the method comprising:

fetching, from a graphics data memory into a cache, graphics data items which are to be used in processing one of the tiles; and

reading the graphics data items from the cache for use in processing said one of the tiles, wherein the method further comprises;

determining indicators for the graphics data items, wherein, for each of the graphics data items, the indicator for that graphics data item is indicative of a number of tiles with which that graphics data item is associated;

determining which of the graphics data items in the cache to evict based on the determined indicators; and

evicting the determined graphics data items from the cache.

5. The method of claim 1 further comprising determining bounding regions for the graphics data items wherein a particular graphics data item is associated with a particular tile if the bounding region for that graphics data item at least partially overlaps the particular tile,

and wherein for each of the graphics data items, the indicator for that graphics data item is initially determined based on a number of tiles which found to at least partially overlap the bounding region for that graphics data item.

13. The method of claim 1 wherein for each of the graphics data items, the indicator is a count of the number of tiles with which that graphics data item is associated.

14. The method of claim 13 further comprising decrementing the count for a particular graphics data item when a tile with which the particular graphics data item is associated has been processed.

15. The method of claim 13 wherein said determining which of the graphics data items in the cache to evict comprises determining which of the graphics data items in the cache has the lowest count.

16. The method of claim 13 wherein said determining which of the graphics data items in the cache to evict comprises determining whether any of the graphics data items have a count equal to zero.

17. The method of claim 14 wherein if the count of the particular graphics data item is one when a tile with which the particular graphics data item is associated has been processed then the method comprises invalidating the cache entry corresponding to the particular graphics data item.

18. The method of claim 13 wherein the count is limited, such that for each of the graphics data items, if the number of tiles with which that graphics data item is associated is greater than a predetermined maximum, the count is determined to be equal to the predetermined maximum.

19. The method of claim 18 wherein the count is decremented only if the count is less than the predetermined maximum.

21. The method of claim 1 wherein for each of the graphics data items, the indicator for that graphics data item indicates one of four conditions, the four conditions being:

(i) that the number of tiles with which that graphics data item is associated is equal to one,

(ii) that the number of tiles with which that graphics data item is associated is equal to two,

(iii) that the number of tiles with which that graphics data item is associated is equal to three or four, and

(iv) that the number of tiles with that graphics data item is associated is greater than four.

2. (canceled)

6. The method of claim 5 when dependent upon claim 2 wherein for each of the graphics data items, the bounding region for that graphics data item contains all of the graphics data items in the graphics data set of that graphics data item.

3. (canceled)

4. (canceled)

7-12. -12. (canceled)

20. (canceled)

22-26. -26. (canceled)

27. A tile-based graphics system having a rendering space sub-divided into a plurality of tiles with which graphics data items are associated, the tile-based graphics system comprising a processing unit configured to:

fetch, from a graphics data memory into a cache, graphics data items which are to be used in processing one of the tiles;

read the graphics data items from the cache for use in processing said one of the tiles;

determine indicators for the graphics data items, wherein, for each of the graphics data items, the indicator for that graphics data item is indicative of the number of tiles with which that graphics data item is associated;

determine which of the graphics data items in the cache to evict based on the determined indicators; and

evict the determined graphics data items from the cache.

28. The system of claim 27 wherein the graphics data items are stored in graphics data sets in the graphics data memory, each of the graphics data sets comprising one or more of the graphics data items.

29. The system of claim 28 wherein a particular graphics data item is associated with a particular tile if a graphics data item in the graphics data set comprising the particular graphics data item is to be used to process the particular tile,

and wherein for each of the graphics data items, the indicator for that graphics data item is indicative of the number of tiles which are processed using a graphics data item in the graphics data set comprising that graphics data item.

30. The system of claim 27 wherein a particular graphics data item is associated with a particular tile if the particular graphics data item is to be used to process the particular tile,

and wherein for each of the graphics data items, the indicator for that graphics data item is indicative of the number of tiles which are processed using that graphics data item.

39. The system of claim 27 wherein for each of the graphics data items, the indicator is a count of the number of tiles with which that graphics data item is associated.

40. The system of claim 39 wherein the processing unit is further configured to decrement the count for a particular graphics data item when a tile with which the particular graphics data item is associated has been processed.

41. The system of claim 39 wherein the processing unit is configured to determine which of the graphics data items in the cache to evict by determining which of the graphics data items in the cache has the lowest count.

44. The system of claim 39 wherein the processing unit is configured to place a limit on the count, such that for each of the graphics data items, if the number of tiles with which that graphics data item is associated is greater than a predetermined maximum, the count is determined to be equal to the predetermined maximum.

45. The system of claim 44 wherein the processing unit is configured to decrement the count only if the count is less than the predetermined maximum.

31. The system of claim further comprising determining bounding regions for the graphics data items wherein a particular graphics data item is associated with a particular tile if the bounding region for that graphics data item at least partially overlaps the particular tile,

and wherein for each of the graphics data items, the indicator for that graphics data item is indicative of the number of tiles which at least partially overlap the bounding region for that graphics data item.

34. The system of claim 31 wherein the processing unit is further configured to determine an order in which tiles are to be processed based on the indicators of the graphics data items in the cache and based on the determination of which of the graphics data items are present in each of the tiles.

32-33. -33. (canceled)

35-37. -37. (canceled)

42-43. -43. (canceled)

46-52. -52. (canceled)

53. A processing block of a tile-based graphics system having a rendering space sub-divided into a plurality of tiles with which graphics data items are associated, the processing block comprising:

fetching logic configured to fetch, from a graphics data memory into a cache, graphics data items which are to be used in processing one of the tiles;

determining logic configured to determine indicators for the graphics data items, such that for each of the graphics data items, the indicator for that graphics data item is indicative of the number of tiles with which that graphics data item is associated;

reading logic configured to read the graphics data items from the cache for use in processing said one of the tiles; and

eviction logic configured to;

determine which of the graphics data items in the cache to evict based on the determined indicators; and

evict the determined graphics data items from the cache.

54. (canceled)