Detecting error in safety-critical GPU by monitoring for response to an instruction
A method of detecting an error at a graphics processing unit causes an instruction including a request for a response from a graphics processing unit to be provided to the graphics processing unit. A timer being configured to expire after a time period is initialised, and during the time period the graphics processing unit is monitored for the response from the graphics processing unit. An error is determined to have occurred in response to determining that no response was received from the graphics processing unit before the timer expired.
1. A method of detecting an error at a graphics processing unit, the method comprising:
causing an instruction to be provided to the graphics processing unit, said instruction comprising a request for a response from the graphics processing unit, wherein the instruction requests that the graphics processing unit respond:
immediately upon the graphics processing unit reading the request for response, or
on completing a step of configuring the graphics processing unit in accordance with configuration data, or
on completing a step of determining whether the graphics processing unit is correctly configured in accordance with configuration data;
initialising a timer, said timer being configured to expire after a time period;
monitoring, during said time period, for the response from the graphics processing unit; and
determining that an error has occurred in response to determining that no response is received from the graphics processing unit before the timer expires.
2. The method as claimed in claim 1 , wherein the method further comprises causing the graphics processing unit to be reset in response to determining that the error has occurred.
3. The method as claimed in claim 1 , wherein the graphics processing unit is configured to perform safety-critical rendering.
4. The method as claimed in claim 1 , wherein the instruction is for initialising rendering of graphical data at the graphics processing unit, and wherein the time period is determined in dependence on the graphical data to be rendered.
5. The method as claimed in claim 4 , wherein the graphical data is safety critical graphical data.
6. The method as claimed in claim 1 , wherein the instruction is for initialising rendering of graphical data at the graphics processing unit, and wherein the time period is determined in dependence on the expected duration of the graphical processing being initialised.
7. The method as claimed in claim 1 , wherein the method comprises determining, by a safety controller external to the graphics processing unit, that the error has occurred in response to determining that no response is received from the graphics processing unit before the timer expires.
8. The method as claimed in claim 1 , wherein the instruction further comprises the configuration data.
9. A graphics processing system comprising a graphics processing unit and a safety controller, in which the safety controller is configured to:
cause an instruction to be provided to the graphics processing unit, said instruction comprising a request for a response from the graphics processing unit, wherein the instruction requests that the graphics processing unit respond:
immediately upon the graphics processing unit reading the request for response, or
on completing a step of configuring the graphics processing unit in accordance with configuration data, or
on completing a step of determining whether the graphics processing unit is correctly configured in accordance with configuration data;
initialise a timer, said timer being configured to expire after a time period;
monitor, during said time period, for the response from the graphics processing unit; and
determine that an error has occurred if no response is received from the graphics processing unit before the timer expires.
10. A graphics processing system comprising a graphics processing unit and a safety controller, in which the safety controller is configured to:
generate configuration data for the graphics processing unit;
cause an instruction comprising the configuration data and a request fora response from the graphics processing unit to be provided to the graphics processing unit, wherein the instruction requests that the graphics processing unit respond:
immediately upon the graphics processing unit reading the request for response, or
on completing a step of configuring the graphics processing unit in accordance with configuration data, or
on completing a step of determining whether the graphics processing unit is correctly configured in accordance with configuration data;
initialise a timer, said timer being configured to expire after a time period;
monitor, during the time period, for the response from the graphics processing unit;
configure the graphics processing unit in accordance with the configuration data;
determine whether the graphics processing unit is correctly configured in accordance with the configuration data; and
determine that an error has occurred in response to determining that:
(i) the graphics processing unit is not correctly configured in accordance with the configuration data; or
(ii) no response is received from the graphics processing unit before the timer expires.
11. The graphics processing system as claimed in claim 10 , in which the safety controller is further configured to cause the graphics processing unit to be reset in response to determining that the error has occurred.
12. The graphics processing system as claimed in claim 10 , wherein the safety controller is external to the graphics processing unit.
13. The graphics processing system as claimed in claim 10 , wherein the configuration data comprises one or more register entries to be written into one or more registers of the graphics processing unit, said configuration data specifying a configuration to be adopted by the graphics processing unit.
14. The graphics processing system as claimed in claim 13 , in which the safety controller is further configured to determine whether the graphics processing unit is correctly configured in accordance with the configuration data by determining whether the configuration data has been correctly written into one or more registers of the graphics processing unit.
15. The graphics processing system as claimed in claim 13 , in which the safety controller is further configured to determine whether the graphics processing unit has been correctly configured in accordance with the configuration data by:
reading the one or more register entries corresponding to the configuration data back from each of the one or more registers of the graphics processing unit after the graphics processing unit has been configured; and
comparing the one or more register entries read back from each register with an expected data entry for that register specified by the configuration data.
16. The graphics processing system as claimed in claim 13 , in which the safety controller is further configured to determine whether the graphics processing unit has been correctly configured in accordance with the configuration data by:
reading the one or more register entries corresponding to the configuration data back from each of the one or more registers of the graphics processing unit after the graphics processing unit has been configured;
performing a checksum over the one or more register entries read back from the one or more registers;
performing a checksum over the configuration data; and
comparing the results of said checksums.
17. The graphics processing system as claimed in claim 10 , wherein the graphics processing unit is configured to perform safety-critical rendering.
18. The graphics processing system as claimed in claim 10 , wherein the configuration data is for initialising rendering of graphical data at the graphics processing unit.
19. The graphics processing system as claimed in claim 18 , wherein the graphical data is safety critical graphical data.