In this chapter the concepts of authoring BIOS tasks (TSK) will be considered.

Transcription

1 Tasks - TSK Introduction In this chapter the concepts of authoring BIOS tasks (TSK) will be considered. Objectives At the conclusion of this module, you should be able to: Describe the fundamental concepts of tasks Demonstrate the use of semaphores in tasks Author TSK code using streams to interface with IOM Create a TSK with the CCS GUI Describe the TSK object Explain the value of double buffers in DSP systems Modify single buffer code to use double buffers Module Topics Tasks - TSK Comparison of Tasks to Software Interrupts Task Scheduling Semaphores (SEM) Task Object Review Lab 5: Adapting the SWI Based System to a TSK BIOS System Integration - Tasks - TSK 5-1

2 Comparison of Tasks to Software Interrupts Comparison of Tasks to Software Interrupts Scheduler States : TSK vs SWI SWI Created TSK Created Inactive post Ready 1 2 completed when highest priority Ready 1 2 Posted preempted Blocked when highest priority Running 1 2 preempted Running 1 2 Terminated Tasks are: ready to run when created by BIOS startup if specified in GCONF by TSK_create() in dynamic systems (mod 11) preemptive blocked when ing on an unavailable resource returned to ready state when resource is posted may be terminated when no longer needed 4 SWI vs. TSK SWI Feature TSK Preemptable - Block, Sus - Delete prior to completion by other threads - User Name, Error Number, Environment Pointer Can interface with SIO faster context switch speed slower - Context preserved across accesses to thread NO Can call SEM_() system Stack Individual ASM, C API callable by C SEM_ with timeout of 0 is allowed BIOS System Integration - Tasks - TSK

3 Task Scheduling Task Scheduling DSP/BIOS Scheduler Hard R/T Priority Foreground HWI Hardware Interrupts SWI Software Interrupts TSK Tasks HWI priorities set by hardware Fixed number, preemption optional 14 SWI priority levels Any number possible, all preemptive 15 TSK priority levels Any number possible, all preemptive Soft R/T Background IDL Background Continuous loop Non-realtime in nature All TSKs are preempted by all SWIs and HWIs All SWIs are preempted by all HWIs Preemption amongst HWI is determined by user In absence of HWI, SWI, and TSK, IDL functions run in loop 7 Thread Preemption Example HWI SWI 2 SWI 1 TSK 2 TSK 1 sem2 post post swi1 return swi2 return interrupt interrupt return return post sem2 return interrupt sem2 sem1 post swi2 return post sem1 post sem2 return sem2 sem1 IDL interrupt Events over time 8 BIOS System Integration - Tasks - TSK 5-3

4 Semaphores (SEM) Semaphores (SEM) Task Code Topology - SEM Posting Void Void taskfunction( ) {{ / / Prolog / / while ( condition ){ SEM_() / / Process / / }} / / Epilog / / }} Initialization (runs once only) Processing loop - option: termination condition Wait for resources to be available Perform desired DSP work... Shutdown (runs once - at most) TSK can encompass three phases of activity SEM can be used to signal resource availability to TSK SEM_() blocks TSK until next buffer is available BIOS System Integration - Tasks - TSK

5 Semaphores (SEM) Semaphore Pend SEM_(&sem, timeout) Pend yes timeout = 0 no false Count > 0 true Decrement count timeout expires Block task SEM posted Semaphore Structure: Non-negative 16-bit counter Pending queue (FIFO) Return FALSE #define SYS_FOREVER (Uns) #define SYS_POLL (Uns) -1 0 // wait forever // don t wait Return TRUE 11 Semaphore Post SEM_post(&sem) Post Increment count False Task ing on sem? True Ready first waiting task Semaphore Structure: Non-negative count Pending queue (FIFO) Return Task switch will occur if higher priority task is made ready 12 BIOS System Integration - Tasks - TSK 5-5

6 Semaphores (SEM) Static Creation of SEM Creating a new SEM Obj 1. right click on SEM mgr 2. select Insert SEM 3. type object name 4. right click on new SEM 5. select Properties 6. indicate desired User Comment (FYI) Initial SEM count var mysem = SEM.create("mySem"); mysem.comment = "my SEM"; mysem.count = 0; 13 SEM API Summary SEM API SEM_ SEM_post SEM_Binary SEM_postBinary SEM_count SEM_reset SEM_new SEM_ipost Description Wait for the semaphore Signal the semaphore Wait for binary semaphore to = 1 Write a 1 to the specified semaphore Get the current semaphore count Reset SEM count to the argument-specified value Puts specified count value in specified SEM SEM_post in ISR obsolete use SEM_post SEM_create SEM_delete Create a semaphore Delete a semaphore Mod BIOS System Integration - Tasks - TSK

7 Task Object Task Object Static Creation of TSK Creating a new TSK 1. right click on TSK mgr 2. select Insert TSK 3. type TSK name 4. right click on new TSK 5. select Properties 8. indicate desired priority stack properties function arguments etc 16 Task Object Concepts... Task object: Pointer to task function Priority: changable Pointer to task s stack Stores local variables Nested function calls makes blocking possible Interrupts run on the system stack Pointer to text name of TSK Environment: pointer to user defined structure: mytsk inst2 fxn environ priority stack name fxn environ priority stack name 6 lpf1 6 lpf2 struct struct myenv myenv TSK stack struct struct myenv myenv TSK stack C fxn, eg: bk FIR TSK_setenv(TSK_self(),&myEnv); hmyenv = TSK_getenv(&myTsk); 17 BIOS System Integration - Tasks - TSK 5-7

8 Review Review TSK API Summary TSK API TSK_exit TSK_getenv TSK_setenv TSK_getname TSK_create TSK_delete Description Terminate execution of the current task Get task environment Set task environment Get task name Create a task ready for execution Mod 11 Delete a task Most TSK API are used outside the TSK so other parts of the system can interact with or control the TSK Most TSK API are to allow: TSK scheduler management (Mod 7) TSK monitor & debug (Mod 8) Dynamic creation & deletion of TSK (Mod 11) TSK author usually has no need for any TSK API within the TSK code itself 20 TSK API Summary TSK API Description TSK_settime Set task statistics initial time TSK_deltatime Record time elapsed since TSK made ready TSK_getsts Get task STS object TSK_seterr Set task error number TSK_geterr Get task error number TSK_stat Retrieve the status of a task TSK_checkstacks Check for stack overflow TSK_disable Disable DSP/BIOS task scheduler TSK_enable Enable DSP/BIOS task scheduler TSK_getpri Get task priority TSK_setpri Set a tasks execution priority TSK_tick Advance system alarm clock TSK_itick Advance system alarm clock (ISR) TSK_sleep Delay execution of the current task TSK_time Return current value of system clock TSK_yield Yield processor to equal priority task Mod 8 Mod BIOS System Integration - Tasks - TSK

9 Lab 5: Adapting the SWI Based System to a TSK Lab 5: Adapting the SWI Based System to a TSK The lab adaptation will include of the following: In the TCF file, replace the processing SWI with a TSK and create a SEM In isr.c: Post a SEM instead of the SWI In proc.c: Add a while loop and SEM_ to the procbuf() function Build, download, run, and verify the correct operation of the new solution Copy the solution files to C:\BIOS\mySols\05 For a more rigorous test of your skills if time permits you can attempt this lab given the information on this page alone. In most cases, it is recommended to follow the implementation steps on the next page. Note that given the experience gained in prior labs, the procedures on the next page are briefer and more demanding. Audio In (48 KHz) Audio Out (48 KHz) Lab 5: Task Thread - TSK BIOS\Labs\HW ADC AIC33 DAC AIC33 mcbsp.c McBSP DRR McBSP DXR BIOS\Labs\Algos FIR.c FIR Code coeffs.c Coefficients BIOS\Labs\Work israudio HWI12 pinbuf[bkcnt]=mcbsp_read MCBSP_write(pOutBuf[bkCnt]) if(bkcnt=2buf) QUE_put(&from DevQbufs) SEM_post(&mySem) bkcnt=0; procbuf tskprocbuf while() SEM_(&mySem) for (i =0, i<hist; i ++) pin][i]=ppriorin][2buf-hist]; if( sw0 == 1 ) FIR(in[pIn-HIST],out[pOut]) else {pout[i]=pin[i]} Begin with the SWI-based buffered system Modify SWI to run as TSK; add SEM_ and while loop TCF: remove SWI obj, add TSK and SEM objs Modify HWI to post SEM instead of SWI Build, load, test, verify performance 23 A solved set of these files are found in C:\BIOS\Sols\05. If this particular chapter is of lesser interest, or if there is a time constraint, you may instead copy the solution files to the Work directory, skip over the authoring steps, and move directly to seeing how the completed code looks and works. BIOS System Integration - Tasks - TSK 5-9

10 Lab 5: Adapting the SWI Based System to a TSK Below are the steps required to adapt the SWI-based processing thread to a TSK-based version. 1. If necessary, start CCS and open the solution from lab 4b. Build the project and verify it performs properly In mywork.tcf : 2. Replace the SWI that called procbuf with a TSK named tskprocbuf 3. Create a SEM named sembufrdy In isr.c 4. Replace the SWI_post() with a SEM_post() of sembufrdy In proc.c 5. Add a while(1) loop around all the iterative code in procbuf. 6. Add a SEM_ on the newly created semaphore as the first line of the while loop Having completed the adaptation steps you can now: 7. Build, load, run, and verify the correct operation of the new solution 8. (optional) Relocate the initialization of the messages and todevq to the prolog of the TSK. While not required, this makes the TSK a more complete (and instantiable) component 9. Using windows explorer, copy all files from C:\BIOS\Labs\Work to C:\BIOS\mySols\ BIOS System Integration - Tasks - TSK