1. TI BIOS
TSK – Task Authoring
15 November 2018
Dr. Veton Këpuska

2. 1 2 3 4 5 6 Objectives Describe the fundamental concepts of tasks
Demonstrate the use of semaphores in tasks 2
Author TSK code using simple data block pointers 3
Create a TSK with the CCS GUI 4
Describe the TSK object 5
Modify SWI based code to employ TSK 6
15 November 2018
Dr. Veton Këpuska 2

3. 1 2 3 4 5 6 Outline TSK vs. SWI TSK Scheduling Semaphores (SEM)
Task Object 4
Review 5
Lab 6
15 November 2018
Dr. Veton Këpuska 3

4. 1 2 3 4 5 6 Tasks vs. SWI TSK vs. SWI TSK Scheduling Semaphores (SEM)
Task Object 4
Review 5
Lab 6
15 November 2018
Dr. Veton Këpuska 3

5. TSK vs. SWI
15 November 2018
Dr. Veton Këpuska

6. Scheduler States: TSK vs. SWI
Created
Created
Inactive
post
Ready 1 2
Posted
when highest priority
Ready 1 2
Blocked
preempted
completed
when highest priority
preempted
pend
Running 1 2
Running 1 2
Terminated
15 November 2018
Dr. Veton Këpuska

7. Tasks Are: Ready to Run when Created Preemptive
by BIOS startup if specified in GCONF
by TSK_create() in dynamic systems (mod 11)
Preemptive
Blocked when Pending on an unavailable resource
Returned to Ready state when resource is posted
May be Terminated when no longer needed
15 November 2018
Dr. Veton Këpuska

8. SWI vs. TSK SWI Feature TSK  Preemptable - Block, Suspend
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_pend()
System
Stack
Individual
ASM, C
API callable by C
* SEM_pend with timeout of 0 is allowed
15 November 2018
Dr. Veton Këpuska

9. 1 2 3 4 5 6 TSK Scheduling TSK vs. SWI TSK Scheduling Semaphores (SEM)
Task Object 4
Review 5
Lab 6
15 November 2018
Dr. Veton Këpuska 3

10. Task Scheduling
15 November 2018
Dr. Veton Këpuska

11. DSP/BIOS Scheduler HWI SWI Priority TSK IDL 15 TSK priority levels
Hardware Interrupts
HWI priorities set by hardware
Fixed number, preemption optional
Hard R/T
Foreground
SWI
Software Interrupts
14 SWI priority levels
Any number possible, all preemptive
Priority
TSK
Tasks
15 TSK priority levels
Any number possible, all preemptive
Background
IDL
Background
Continuous loop
Non-realtime in nature
Soft R/T
15 November 2018
Dr. Veton Këpuska

12. DSP/BIOS Scheduler 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 a loop
15 November 2018
Dr. Veton Këpuska

13. Thread Preemption Example
Digital Systems: Hardware Organization and Design
11/15/2018
Thread Preemption Example
post swi1
post swi2
post sem2
return
return
return
post swi2
return
HWI
post sem1
post sem2
return
SWI 2
return
return
SWI 1
pend sem2
pend sem2
pend sem2
interrupt
TSK 2
pend sem1
pend sem1
TSK 1
The main point of this slide is that BIOS (scheduler) manages priorities for you. Each thread (SWI, TSK) runs unaware of the others around it. As INTs post SEMs and SWIs, higher priority threads become ready, and BIOS will run each in order of priority, dropping down to lower levels as higher ones are satisfied or block waiting for additional resources. All this is automatic to the user - just write each thread, assign it a priority, and BIOS does the rest.
A few points to note: SWIs run to completion - like a function call - a one shot, if you like. TSKs, instead, usually linger much longer - their execute phase is a while loop. They block when they run out of resources, and lower threads (or idle) can run until the requested resource arrives. In Bridge, TSKs are dynamically created and can be deleted, but normally are ready, running, or blocked.
An interesting point: if RMS is a TSK of low priority (1), how come it’s running when TSK1 and TSK2 are ready? Recall that RMS implements the create phase of each TSK, and until the gateway puts the TSK in run mode, its priority is (minus) -1, thus TSK1 and TSK2 have no priority until elevated with DSPNode_run().
interrupt
interrupt
IDL
interrupt
Events over time
15 November 2018
Dr. Veton Këpuska
Architecture of a Respresentative 32 Bit Processor

14. 1 2 3 4 5 6 TSK Scheduling TSK vs. SWI TSK Scheduling Semaphores (SEM)
Task Object 4
Review 5
Lab 6
15 November 2018
Dr. Veton Këpuska 3

15. Semaphores (SEM)
15 November 2018
Dr. Veton Këpuska

16. Task Code Topology: SEM Posting
Void taskFunction(…) { /* Prolog */ while (‘condition’) { SEM_pend(); /* 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)
15 November 2018
Dr. Veton Këpuska

17. Task Code Topology: SEM Posting
TSK can encompass three phases of activity
SEM can be used to signal resource availability to TSK
SEM_pend() blocks TSK until next buffer is available
15 November 2018
Dr. Veton Këpuska

18. Semaphore Pending: SEM_pend()
Digital Systems: Hardware Organization and Design
11/15/2018
Semaphore Pending: SEM_pend()
SEM_pend(&sem,timeout)
Pend
Count > 0
yes
false
true
Decrement count
timeout = 0 no
Semaphore Structure:
Non-negative 16-bit counter
Pending queue (FIFO)
timeout expires
Block task
Return
FALSE
SEM
posted
Return
TRUE
#define SYS_FOREVER (Uns) -1
// wait forever
#define SYS_POLL (Uns)
// don’t wait
15 November 2018
Dr. Veton Këpuska
Architecture of a Respresentative 32 Bit Processor

19. Semaphore Post: SEM_post()
SEM_post(&sem)
Post
Task pending on sem?
Ready first waiting task
Increment count
False
True
Semaphore Structure:
Non-negative count
Pending queue (FIFO)
Task switch will occur if higher priority task is made ready
Return
15 November 2018
Dr. Veton Këpuska

20. Creation of SEM Object Creating a new SEM Obj right click on SEM mgr
select “Insert SEM”
type object name
right click on new SEM
select “Properties”
indicate desired
User Comment (FYI)
Initial SEM count
var mySem = SEM.create("mySem");
mySem.comment = "my SEM";
mySem.count = 0;
15 November 2018
Dr. Veton Këpuska

21. Digital Systems: Hardware Organization and Design
11/15/2018
SEM API Summary
SEM API
Description
SEM_pend
Wait for the semaphore
SEM_post
Signal the semaphore
SEM_pendBinary
Wait for binary semaphore to = 1
SEM_postBinary
Write a 1 to the specified semaphore
SEM_count
Get the current semaphore count
SEM_reset
Reset SEM count to the argument-specified value
SEM_new
Puts specified count value in specified SEM
SEM_ipost
SEM_post in ISR – obsolete – use SEM_post
SEM_create
Create a semaphore
SEM_delete
Delete a semaphore
Mod 11
15 November 2018
Dr. Veton Këpuska
Architecture of a Respresentative 32 Bit Processor

22. 1 2 3 4 5 6 TSK Scheduling TSK vs. SWI TSK Scheduling Semaphores (SEM)
Task Object 4
Review 5
Lab 6
15 November 2018
Dr. Veton Këpuska 3

23. Task Object
15 November 2018
Dr. Veton Këpuska

24. Static Creation of TSK Creating a new TSK right click on TSK mgr
select “Insert TSK”
type TSK name
right click on new TSK
select “Properties”
indicate desired
priority
stack properties
function
arguments
etc
15 November 2018
Dr. Veton Këpuska

25. Task Object Concepts... Task object: TSK_setenv(TSK_self(),&myEnv);
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
fxn *
environ
priority 6
stack
name
lpf1
struct myEnv
TSK stack
C fxn, eg: bk FIR
inst2
fxn *
environ
priority 6
stack
name
lpf2
struct myEnv
TSK stack
TSK_setenv(TSK_self(),&myEnv);
hMyEnv = TSK_getenv(&myTsk);
15 November 2018
Dr. Veton Këpuska

26. TSK Object typedef struct TSK_Stat {
TSK_Attrs attrs; // task attributes TSK_Mode mode; // running, blocked... Ptr sp; // stack ptr size_t used; // stack max
} TSK_Stat;
typedef struct TSK_Obj { // from TSK.h
KNL_Obj kobj; // kernel object Ptr stack; // used w TSK_delete() size_t stacksize; // ditto Int stackseg; // stack alloc’n RAM String name; // printable name Ptr environ; // environment pointer Int errno; // TSK_seterr()/_geterr() Bool exitflag; // FALSE for server tasks
} TSK_Obj, *TSK_Handle;
typedef struct TSK_Attrs {
Int priority; // task priority Ptr stack; // stack supplied size_t stacksize; // size of stack Int stackseg; // stack alloc’n seg Ptr environ; // environment pointer String name; // printable name Bool exitflag; // server tasks = false Bool initstackflag; // FALSE: no stack init
} TSK_Attrs;
struct KNL_Obj { // from KNL.h
QUE_Elem ready; // ready/sem queue QUE_Elem alarm; // alarm queue elem QUE_Elem setpri; // set priority queue QUE_Handle queue; // task's ready queue Int priority; // task priority Uns mask; // 1 << priority Ptr sp; // current stack ptr Uns timeout; // timeout value Int mode; // blocked, ready, STS_Obj *sts; // for TSK_deltatime() Bool signalled; // woken by sem or t-out };
typedef struct TSK_Config {
Int STACKSEG; Int PRIORITY; size_t STACKSIZE; Fxn CREATEFXN; Fxn DELETEFXN; Fxn EXITFXN; Fxn SWITCHFXN; Fxn READYFXN;
} TSK_Config;
15 November 2018
Dr. Veton Këpuska

27. 1 2 3 4 5 6 TSK Scheduling TSK vs. SWI TSK Scheduling Semaphores (SEM)
Task Object 4
Review 5
Lab 6
15 November 2018
Dr. Veton Këpuska 3

28. Review
15 November 2018
Dr. Veton Këpuska

29. TSK API Summary TSK API Description TSK_exit
Terminate execution of the current task
TSK_getenv
Get task environment
TSK_setenv
Set task environment
TSK_getname
Get task name
TSK_create
Create a task ready for execution
TSK_delete
Delete a task
Mod 11
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
15 November 2018
Dr. Veton Këpuska

30. TSK API Summary TSK API Description Mod 8 Mod 7 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
Mod 8
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 7
15 November 2018
Dr. Veton Këpuska 21

31. 1 2 3 4 5 6 TSK Scheduling TSK vs. SWI TSK Scheduling Semaphores (SEM)
Task Object 4
Review 5
Lab 6
15 November 2018
Dr. Veton Këpuska 3

32. Lab
15 November 2018
Dr. Veton Këpuska

33. Lab 5: Task Thread - TSK BIOS\Labs\HW BIOS\Labs\Work Audio In (48 KHz)
isrAudio
pInBuf[bkCnt]=MCBSP_read MCBSP_write(pOutBuf[bkCnt])
if(bkCnt=2*BUF) { QUE_put(&from DevQbufs)
SEM_post(&mySem) bkCnt=0; }
HWI12
ADC AIC33
McBSP DRR
mcbsp.c
DAC AIC33
McBSP DXR
Audio Out (48 KHz)
BIOS\Labs\Algos
tskProcBuf
procBuf
while()
SEM_pend(&mySem)
for (i =0, i<HIST; i ++)
pIn[i]=pPriorIn[2*BUF-HIST];
if( sw0 == 1 )
FIR(in[pIn-HIST],out[pOut])
else {pOut[i]=pIn[i]}
FIR.c
FIR Code
coeffs.c
Coefficients
15 November 2018
Dr. Veton Këpuska

34. Lab 5: Task Thread - TSK Begin with the SWI-based buffered system
Modify SWI to run as TSK; add SEM_pend 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
15 November 2018
Dr. Veton Këpuska

35. Lab 5 : Summary In the procBuf (TSK) function
In the TCF file:
replace the processing SWI with a TSK
create a SEM
In audio.c:
In the isrAudio (HWI) function:
Post a SEM instead of the SWI
In the procBuf (TSK) function
Add a while loop and SEM_pend to the remaining code in procBuf()
Build, download, run, and verify the correct operation of the new solution
Optionally, copy the solution files to C:\BIOS\mySols\05
15 November 2018
Dr. Veton Këpuska

36. Lab 5: Procedure Overview
Below are the steps required to adapt the SWI-based processing thread to a TSK-based version.
If necessary, start CCS and open the solution from lab 4. Build the project and verify it performs properly
In myWork.tcf :
Replace the SWI that called procBuf with a TSK named tskProcBuf
Create a SEM named semBufRdy
In isr.c
Replace the SWI_post() with a SEM_post() of semBufRdy
15 November 2018
Dr. Veton Këpuska

37. Lab 5: Procedure Overview
In proc.c
Add a while(1) loop around all the iterative code in procBuf.
Add a SEM_pend on the newly created semaphore as the first line of the while loop
Having completed the adaptation steps you can now:
Build, load, run, and verify the correct operation of the new solution
(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
Using windows explorer, copy all files from C:\BIOS\Labs\Work to C:\BIOS\mySols\05
15 November 2018
Dr. Veton Këpuska

38. Lab Details Observations:
HWI – based lab 3
Observations:
Moving from SWI to TSK showed results within 0.1% of being the same
So… the ‘extra overhead’ of TSK vs. SWI doesn’t really amount to much at all, and could easily be countered by a small increase in buffer size, which will have much greater effect than thread type
Filter
Debug
Release
Off
18%
4.7% On
61%
6.5%
SWI – based lab 4
Filter
Debug
Release
Off
3.8%
2.3% On
45%
3.7%
TSK – based lab 5
Filter
Debug
Release
Off
3.8%
2.5% On
45%
15 November 2018
Dr. Veton Këpuska

39. TI BIOS TSK
END
15 November 2018
Dr. Veton Këpuska