System and method for handling display device requests for display data from a frame buffer

• US 20030169262A1
• Filed: 03/11/2002
• Published: 09/11/2003
• Est. Priority Date: 03/11/2002
• Status: Active Grant

• Current Assignee: Oracle America, Inc. (Oracle Corporation)
• Original Assignee: Sun Microsystems Incorporated (Oracle Corporation)
• Inventors: Tang, Yan Yan, Lavelle, Michael G.
• Granted Patent: US 6,806,883 B2
• Time in Patent Office: Days
• US Class Current: 345/531
• CPC Class Codes: G09G 2360/12 Frame memory handling
• CPC Class Codes: G09G 5/001 Arbitration of resources in a display system, e.g. control of access to frame buffer by video controller and/or main processor
• CPC Class Codes: G09G 5/363 Graphics controllers
• CPC Class Codes: G09G 5/39 Control of the bit-mapped memory
• CPC Class Codes: G09G 5/393 Arrangements for updating the contents of the bit-mapped memory
• CPC Class Codes: G09G 5/395 Arrangements specially adapted for transferring the contents of the bit-mapped memory to the screen G09G5/399 takes precedence

Abstract

A graphics system may include a frame buffer, a processing device coupled to access data in the frame buffer, a frame buffer interface coupled to the frame buffer, and an output controller configured to assert a request for display data to provide to a display device. The frame buffer interface may receive the request for display data from the output controller and delay providing the request for display data to the frame buffer if the processing device is currently requesting access to a portion of the frame buffer targeted by the request for display data. For example, if the frame buffer includes several memory banks and the request for display data targets a first bank, the frame buffer interface may delay providing the request for display data to the frame buffer if the processing device is currently requesting access to the first bank.

Claims

1. A graphics system comprising:

a frame buffer;

a processing device coupled to the frame buffer and configured to access data in the frame buffer;

a frame buffer interface coupled to the frame buffer;

an output controller coupled to the frame buffer interface and configured to provide display data to a display device, wherein the output controller is configured to assert a first request for display data;

wherein the frame buffer interface is configured to receive the first request for display data from the output controller and to delay providing the first request for display data to the frame buffer if the processing device is currently accessing a portion of the frame buffer targeted by the first request for display data.

2. The graphics system of claim 1, wherein the frame buffer comprises a plurality of banks of memory, wherein the first request for display data targets a first one of the banks of memory and the processing device is currently accessing the first one of the banks.

9. The graphics system of claim 1, wherein the frame buffer interface is configured to delay providing the first request for display data to the frame buffer if the processing device is currently asserting a first type of request and to not delay providing the first request for display data to the frame buffer if the processing device is currently asserting a second type of request.

10. The graphics system of claim 1, wherein the first request comprises a first bank request targeting a first bank in a first memory device in the frame buffer and a second bank request targeting a second bank in a second memory device, wherein the frame buffer interface is configured to delay providing the first request for display data to the frame buffer if the processing device is currently requesting access to either the first bank in the first memory device or the second bank in the second memory device.

11. The graphics system of claim 1, wherein the first request comprises a first bank request targeting a first bank in a first memory device in the frame buffer and a second bank request targeting a second bank in a second memory device, wherein the frame buffer interface is configured to provide the first bank request to the frame buffer at a different time than the second bank request is provided to the frame buffer.

12. The graphics system of claim 11, wherein the frame buffer interface is configured to initiate a timer in response to receiving the first request, wherein the frame buffer interface is configured to provide both the first bank request and the second bank request to the frame buffer upon expiration of the timer.

3. A graphics system comprising:

a frame buffer;

a processing device coupled to the frame buffer and configured to access data in the frame buffer;

a frame buffer interface coupled to the frame buffer;

an output controller coupled to the frame buffer interface and configured to provide display data to a display device, wherein the output controller is configured to assert a first request for display data;

wherein the frame buffer interface is configured to receive the first request for display data from the output controller and to delay providing the first request for display data to the frame buffer if the processing device is currently requesting access to a portion of the frame buffer targeted by the first request for display data.

4. The graphics system of claim 3, wherein the frame buffer comprises a plurality of banks of memory, wherein the first request for display data targets a first one of the banks of memory and the processing device is currently requesting access to the first one of the banks.

5. The graphics system of claim 4, wherein the frame buffer interface is configured to initiate a timer in response to receiving the first request, wherein the frame buffer interface is configured to provide the request to the frame buffer in response to expiration of the timer, wherein the processing device is requesting access to the first one of the banks when the timer expires.

6. The graphics system of claim 4, wherein the frame buffer interface includes a queue to store pending requests asserted by the processing device, wherein the frame buffer interface is configured to prioritize selection of a pending request from the queue over selection of the first request unless the timer has expired, wherein the frame buffer interface is configured to select the first request instead of selecting a pending request from the queue if the timer has expired.

7. The graphics system of claim 4, wherein the frame buffer interface is configured to receive a second request from the output controller;

wherein the frame buffer interface is configured to provide the second request to the frame buffer a preselected number of cycles after providing the first request to the frame buffer.

8. The graphics system of claim 7, wherein the frame buffer interface is configured to initiate a second timer in response to receiving the second request, wherein the frame buffer interface is configured to provide the second request to the frame buffer in response to the second timer expiring, wherein the processing device is requesting access to the portion of the frame buffer targeted by the second request when the second timer expires.

13. A method of operating a graphics system, the method comprising:

receiving a display request requesting data stored in a frame buffer;

if access to a bank within the frame buffer targeted by the display request is currently being requested by a processing device, delaying to provide the display request to the frame buffer until the processing device is not requesting access to the bank targeted by the display request;

the frame buffer outputting data in response to receiving the display request; and

displaying the data output by the frame buffer on a display device.

14. The method of claim 13, further comprising:

initiating a timer in response to said receiving; and

providing the display request to the frame buffer upon expiration of the timer, wherein the processing display is requesting access to the bank targeted by the display request when the timer expires.

15. The method of claim 14, further comprising:

storing a processing request for data stored in the frame buffer asserted by the processing device in a first queue;

storing the display request in a second queue in response to said receiving;

if the processing request and the display request both target the bank in the frame buffer and the timer has not yet expired, providing the processing request from the first queue to the frame buffer instead of providing the display request from the second queue to the frame buffer; and

if the timer has expired, providing the display request from the second queue to the frame buffer.

16. The method of claim 14, further comprising:

receiving a second display request; and

providing the second display request to the frame buffer a preselected number of cycles after providing the first request to the frame buffer, wherein the processing device is requesting access to a second bank targeted by the second display request when the second display request is provided to the frame buffer.

17. A graphics system comprising:

means for storing graphics data;

means for processing graphics data, wherein the means for processing graphics data are configured to assert a first set of requests for graphics data stored in the means for storing graphics data;

means for outputting graphics data to a display device, wherein the means for outputting graphics data are configured to assert a second set of requests for graphics data stored in the means for storing graphics data;

means for handling requests, wherein the means for handling requests are coupled to the means for storing graphics data, the means for processing graphics data, and the means for outputting graphics data;

wherein if a first request in the first set of requests is targeting a first portion of the means for storing graphics data and a second request in the second set of requests is also targeting the first portion, the means for handling requests are configured to provide the first request to the means for storing graphics data instead of providing the second request unless a timer initiated when the second request was received by the means for handling requests has expired.

18. A graphics system comprising:

means for storing graphics data;

means for processing graphics data, wherein the means for processing graphics data are configured to assert a first set of requests for graphics data stored in the means for storing graphics data;

means for outputting graphics data to a display device, wherein the means for outputting graphics data are configured to assert a second set of requests for graphics data stored in the means for storing graphics data;

means for handling requests, wherein the means for handling requests are coupled to the means for storing graphics data, the means for processing graphics data, and the means for outputting graphics data;

wherein the means for handling requests are configured to provide the first set of requests and the second set of requests to the means for storing data, wherein the means for handling requests are configured to provide requests in the second set of requests to the means for storing data when there are no pending requests in the first set of requests that target a portion of the means for storing data targeted by the first set of requests.