TI BIOS CLK-PRD Multi-Threaded Systems - PowerPoint Presentation

TI BIOS CLK-PRD Multi-Threaded Systems 15 February 2018 Dr. Veton Këpuska 1

Why DSP/BIOS For most system developers today, more time is spent on software design than on hardware design. This is mainly due to the fact that most of the complex hardware functions are already integrated into standard integrated circuits . System developers simply need to select the right chip to do the right job. System designers can use either dedicated hardware integrated circuits or programmable DSPs to implement DSP functions. 15 February 2018 Dr. Veton Këpuska 2

Why DSP/BIOS The advantages of programmable DSPs are: Scalability – Designers can first decide how much processing power (or MIPS—million instructions per second), memories, and other resources are required to do a certain job, then select the DSP with enough processing resources. If one DSP is not enough, more DSPs can be added until the required processing resources are met. Upgradability – Even after the hardware design is fixed, any change in DSP functions can be implemented easily by making changes in software, and downloading the change to the DSP in seconds. 15 February 2018 Dr. Veton Këpuska 3

Why DSP/BIOS However, compared to dedicated hardware DSP chips to implement DSP functions, programmable DSPs need to manage their resources so that they can be shared among different DSP functions. Hardware resources include the CPU, memory, and peripherals. 15 February 2018 Dr. Veton Këpuska 4

Why DSP/BIOS CPU-sharing – In most systems, the number of DSP functions is much larger than the available number of CPUs. Thus, each CPU must be time-shared among DSP functions. But time-sharing the CPU may cause a critical DSP function to miss its real-time deadline. DSP/BIOS and Code Composer Studio are the tools to make time-sharing CPU much easier and avoid real-time deadline problems . 15 February 2018 Dr. Veton Këpuska 5

Why DSP/BIOS Memory-sharing – Memory-sharing is usually the responsibility of the algorithm developer. Using the C language, static memories can be managed easily. However, when the system gets complex with lots of DSP functions, it is not efficient to store each algorithm’s scratch memory statically. Texas Instruments eXpress DSP Algorithm Standard ( xDAlS ) addresses this issue. The xDAlS is out of the scope of this application report. Peripheral-sharing – In most cases, such as I/O devices, a peripheral can be handled by a dedicated DSP function, which is called a device driver. Peripherals such as the direct memory access controller (DMAC) can also be handled this way. 15 February 2018 Dr. Veton Këpuska 6

Why DSP/BIOS With DSP/BIOS, system designers can develop their DSP systems on programmable DSPs using block diagrams to block out each DSP function, similar to designing using dedicated DSP hardware integrated circuits.As mentioned earlier, DSP/BIOS allows system designers to do two major tasks : real-time monitoring and control , and real-time scheduling and communication. DSP/BIOS provides modules to accomplish these tasks (see Table 1). 15 February 2018 Dr. Veton Këpuska 7

15 February 2018 Dr. Veton Këpuska 8

Introduction In this chapter, the presence of multiple threads within a system will be considered. Ways to control how the scheduler operates will be considered. In addition, the ability within DSP/BIOS to pace threads by time, rather than data availability, will be considered. Special, CLK-PRD DSP/BIOS Module provides two methods of tracking time and hence provides a tool for controlling operations by time: the high and low resolution clock managed by the CLK module and the system clock. For this module the default configuration for the CLK module and system clock will be used. 15 February 2018 Dr. Veton Këpuska 9

Objectives 15 February 2018 Dr. Veton Këpuska 10 2

Module Topics 15 February 2018 Dr. Veton Këpuska 11 3

Module Topics 15 February 2018 Dr. Veton Këpuska 12 3

Multi-Threading 15 February 2018 Dr. Veton Këpuska 13

Multi-Threading Can BIOS keep track of time for me? Can time instead of data availability be used to launch threads? 15 February 2018 Dr. Veton Këpuska 14

Module Topics 15 February 2018 Dr. Veton Këpuska 15 3

CLK – PRD Module of BIOS The CLK module provides methods for gathering timing information and for invoking functions periodically. The CLK module provides real-time clocks with functions to access the low-resolution and high-resolution times. These times can be used to measure the passage of time in conjunction with STS accumulator objects, as well as to add timestamp messages in event logs.15 February 2018 Dr. Veton Këpuska 16

CLK – PRD Module of BIOS DSP/BIOS provides the following timing methods:Timer Counter. This DSP/BIOS counter changes at a relatively fast platform-specific rate. This counter is used only if the Clock Manager is enabled in the CLK Manager Properties.Low-Resolution Time. This time is incremented when the timer counter reaches its target value. When this time is incremented, any functions defined for CLK objects are run.High-Resolution Time. For some platforms, the timer counter is also used to determine the high-resolution time. For other platforms, a different timer is used for the high-resolution time. 15 February 2018 Dr. Veton Këpuska 17

CLK – PRD Module of BIOS Periodic Rate. The PRD functions can be run at a multiple of the clock interrupt rate (the low-resolution rate) if you enable the " Use CLK Manager to Drive PRD" in the PRD Manager Properties.System Clock. The PRD rate, in turn, can be used to run the system clock , which is used to measure TSK-related timeouts and ticks. If you set the "TSK Tick Driven By" in the TSK Manager Properties to "PRD ", the system clock ticks at the specified multiple of the clock interrupt rate (the low-resolution rate). 15 February 2018Dr. Veton Këpuska 18

CLK Module Example of the CLK module driven by a timer on the 'C6x’ Low and high resolution clock calculations 15 February 2018 Dr. Veton Këpuska 19 Period Counter Timer 0,1 = Low Resolution Clock + 1 + Period Interrupt High Resolution Clock System Clock

CKL API There are four main functions for accessing the clock information: CLK_countspms () - Timer counts per millisecond CLK_gethtime () - Get high resolution time CLK_getltime () - Get low resolution time CLK_getprd () - Get period register value The first three functions return values of type LgUns and the last one returns a type Uns. None of them have any parameters. 15 February 2018 Dr. Veton Këpuska 20

BIOS Clock Services CLK API 15 February 2018 Dr. Veton Këpuska 21 CPU clock  4 or 8 Timer Counter Period Timer ISR Timer Interrupt Low Rate Clock High Rate Clock Low Res Clock CLK_countspms CLK_getprd CLK_getltime CLK_gethtime System Tick CLK Object(s) + x f CLK API Description CLK_getltime Get low-resolution time (32-bit value) CLK_gethtime Get high-resolution time (32-bit value) CLK_getprd Get period register value CLK_countspms Get number of hardware timer counts per millisecond

BIOS Clock Services CLK API 15 February 2018 Dr. Veton Këpuska 22 CLK abstracts details of HW timer to provide low-res time / system tick Timer period is set and CLK objects specified in BIOS configuration CLK can drive periodic objects directly, or at different rates as PRD SWICLK time values are often helpful in real-time analysis (next module)

CLK – PRD Module of BIOS Many functions in DSP/BIOS have a timeout associated with them. The system clock is used to determine the timeout. The system clock is configured by the periodic function monitor module (PRD module) and is driven by whatever object or function calls PRD_tick . In the default settings the PRD_tick function is called by the CLK object: PRD_clock (find this by clicking on Scheduling->CLK in the configuration tool). When the timer expires the hardware interrupt CLK_F_isr is run which then increments the low resolution clock and calls the functions for all the CLK objects (find this by clicking on Scheduling->HWI->HWI_INT14). 15 February 2018 Dr. Veton Këpuska 23

CLK – PRD Module of BIOS Since PRD_clock is a CLK object it gets called which in turn calls the function PRD_tick. This increments the system clock. The PRD_tick function then determines if the SWI PRD_swi should run. If it should run then it posts an SWI for PRD_swi. 15 February 2018 Dr. Veton Këpuska 24

Setup of CLK via Configuration Tool Setup of the CLK Module right click on CLK mgr select “Properties”define Low res clock rate via usecs / int optionally , set other parameters as desired 15 February 2018 Dr. Veton Këpuska 25

Setup of CLK via Configuration Tool Optional: Making a new CLK object right click on CLK mgr select “Insert CLK” type CLK name right click on new CLK select “Properties” type function to run 15 February 2018 Dr. Veton Këpuska 26

All CLK objects are invoked each Lo Res tick – PRD fxns can run at different intervals – next... 15 February 2018 Dr. Veton Këpuska 27 Setup of CLK via Configuration Tool

Module Topics 15 February 2018 Dr. Veton Këpuska 28 3

Periodic Functions: PRD Can I have a number of functions, each invoked at a given periodic rate?Can I invoke a function that will run once after a given time has passed? 15 February 2018 Dr. Veton Këpuska 29

DSP/BIOS Periodic Functions A special SWI that provides preemptive scheduling for periodic functions While SIO indicates data available and SEM indicates posting by other thread, when time is the gating event PRD is most ideal choice Also useful for modeling interrupts to simulate peripherals (IO devices) 15 February 2018 Dr. Veton Këpuska 30

Periodic Events – PRD SWI 15 February 2018 Dr. Veton Këpuska 31 Timer ISR System Tick CLK Object(s) PRD_clock ... PRD_tick ... PRD_swi PRD_obj PRD_obj PRD_obj ... PRD Object Period 4 Function funcX () Type continuous Arg0 0 Arg1 0 Period # of ticks before calling fxn Function Function to execute Type Continuous or One-shot

Periodic Events – PRD SWI 15 February 2018 Dr. Veton Këpuska 32 PRD_tick () is invoked by PRD_clock by default (also TSK_tick )PRD_tick() may be called by any desired user function as wellPRD_tick () launches the PRD_swi whichScans the list of PRD_obj’s Determines if the specified time for the given PRD_obj has elapsed If so, the function associated with the PRD_obj is called All PRD_obj functions must complete within ONE system (PRD) tick Recommended: make PRD_swi highest priority SWI If routines are short and tick is long - no problem Long functions can be broken up with posts of other threads

Setup of PRD via Configuration Tool Creating a PRD right click on PRD mgr select “Insert PRD” type PRD name right click on new PRD select “Properties” indicate desired period (ticks) mode function arguments 15 February 2018 Dr. Veton Këpuska 33

Setup of PRD via Configuration Tool A PRD can directly launch a regular SWI by specifying:function: _SWI_post arg0: _ mySWI allowing control of priority, and meeting requirement for all PRDs to complete before the next PRD tick 15 February 2018 Dr. Veton Këpuska 34

TCONF Setup of PRD Module & Object 15 February 2018 Dr. Veton Këpuska 35 PRD.OBJMEMSEG = prog.get (" myMEM "); where to locate PRD Objects PRD.USECLK = "true"; CLK MOD will feed PRD PRD.MICROSECONDS = 1000.0; uSecs /tick – skip if using CLK var myPrd = PRD.create (“ myPrd "); create a PRD Object myPrd.period = 1024; # of ticks between calls to PRD Obj * myPrd.mode = "continuous"; type – continuous or “one-shot” myPrd.fxn = prog.extern (“_ myFxn "); function PRD Obj will run myPrd.arg0 = 0; user arguments - optional myPrd.arg1 = 0; * Underlying interrupt rate is largest binary number divisible into period value, so for lowest overhead, pick a binary number when possible

One-shot Periodic Functions Allows delayed execution of a function by n system ticksPRD_start () invokes each iteration of the one-shot function PRD_stop ()can be used to abort a one-shot prior to timeout Example of use: software watchdog function 15 February 2018 Dr. Veton Këpuska 36 ... 74 75 76 77 78 79 80 81 ... Low-res clock (incremented by system tick) PRD_start () funcX () 0 1 2 3 4 PRD Object X Period 4 Function funcX() Type 1 shot Arg0 0 Arg1 0

PRD API Review PRD API Description PRD_tick Advance tick counter, dispatch periodic functions PRD_start Arm a periodic function for onetime execution PRD_stop Stop a periodic function from execution PRD_getticks Get the current tick counter 15 February 2018 Dr. Veton Këpuska 37 Tick counter can be manually incremented by the user with PRD_tick () One-shot periodic functions are managed with PRD_start () & PRD_stop () Inspection of tick count is possible with PRD_getticks () Continuous periodic functions are set up via the BIOS configuration tool and are generally not managed at run-time via BIOS API

Scheduler Management API 15 February 2018 Dr. Veton Këpuska 38 3

Scheduler Control API Scheduler Control API is designed to control: HWI & IDL processesSWI processes, andTSKIs it possible to alter the behavior of the BIOS scheduler when the need arises? 15 February 2018 Dr. Veton Këpuska 39

Scheduler Management API Generally, threads are automatically managed by BIOS according to the priorities of each thread Sometimes, however, it is desirable to alter the normal BIOS scheduler operation, for example:When deadlines are approaching a thread can temporarily be given higher priority or even exclusive use of the processor When multiple threads share a resource, priorities can be modified to avoid higher priority threads interrupting critical sections of lower priority threads To implement time slicing amongst equal priority threads (equal threads are normally “FIFO” serviced)To allow TSKS to ‘sleep’ for a time 15 February 2018 Dr. Veton Këpuska 40

Scheduler Management API In these cases, API can be invoked to alter the behavior of the scheduler with respect to HWI, SWI, and TSK as required 15 February 2018 Dr. Veton Këpuska 41

Scheduler Management API 15 February 2018 Dr. Veton Këpuska 42 3

HWI & IDL Scheduler Control What kind of control can I have on how hardware interrupts and the idle thread are scheduled by BIOS ?HWI_disable() Creates a period where no asynchronous events may occur HWI_restore () does not necessarily enable interrupts, but instead asserts to state prior to HWI_disable() 15 February 2018 Dr. Veton Këpuska 43

HWI_disable and HWI_restore API 15 February 2018 Dr. Veton Këpuska 44 Interrupts that come in during the period where HWI_disable() is being executed will be held off until HWI is re-enabled (if a given interrupt occurs more than once in this period, the additional events will be lost) oldCSR = HWI_disable (); // “critical section” ... // scheduler inhibited ... HWI_restore ( oldCSR );

HWI and IDL Scheduler API 15 February 2018 Dr. Veton Këpuska 45 HWI, IDL API Description HWI_enable Globally enable hardware interrupts HWI_disable Globally disable hardware interrupts HWI_restore Restore global interrupt enable state IDL_run Make one pass through idle functions*

Interrupt Management Intrinsic Faster than the BIOS API They are not commonly used Not callable by HWI or SWI 15 February 2018 Dr. Veton Këpuska 46 Unsigned int _ disable_interrupts (); Unsigned int _ enable_interrupts (); Void _ restore_interrupts (unsigned int );

Scheduler Management API 15 February 2018 Dr. Veton Këpuska 47 3

SWI Scheduling What kind of control can I have on how software interrupts are scheduled by BIOS? Similar to HWI_disable /HWI_restore SWI_disable – All interrupts that come in during the period where SWI_disable is being executed will be held off until SWI is re-enabled. Concludes with SWI_enable (not “ SWI_restore ”) Acts on SWI scheduling only – HWI continue unchanged Nestable - number of levels managed by BIOS 15 February 2018 Dr. Veton Këpuska 48

Disabling & Enabling Software Interrupts 15 February 2018 Dr. Veton Këpuska 49 SWI_disable (); // “critical section” ... // SWI scheduler inhibited ... SWI_enable ();

Temporary Elevation of SWI Priority SWI_raisepri() can be used to raise the SWI priority.SWI_raisepri() cannot lower priority (actually disables lower priority levels) Priority returns to the original value when the SWI exits Original Priority (“origPrio”) should be a local variable Priority values are bit positions, not integer numbers( eg: priority 7 would be ...0100 0000 b)To elevate a SWI above one (or several other) SWI, use in conjunction with SWI_getpri , as per the example below: 15 February 2018 Dr. Veton Këpuska 50

Temporary Elevation of SWI Priority Example of using SWI_getpri(): 15 February 2018 Dr. Veton Këpuska 51 origPrio = SWI_raisepri (1<<7); // critical section ... // lower prio SWIs inhibited ... SWI_restorepri ( origPrio ); For Priority level “X” select 1<<X as the argument to raisepri origPrio = SWI_raisepri ( SWI_getpri (& swiX )| SWI_getpri (& swiY )); // critical section ... // SWI scheduler inhibited ... SWI_restorepri ( origPrio );

SWI Scheduler API 15 February 2018 Dr. Veton Këpuska 52 SWI API Description SWI_disable Disable software interrupts SWI_enable Enable software interrupts SWI_getpri Return an SWI’s priority mask SWI_raisepri Temporarily raise an SWI’s priority SWI_restorepri Restore an SWI’s priority to object value SWI_self Return address of SWI’s object

Scheduler Management API 15 February 2018 Dr. Veton Këpuska 53 3

TSK Scheduling and Control What kind of control can I have on how tasks are scheduled by BIOS? TSK_disable and TSK_enable Similar to SWI_disable / SWI_enable Acts on TSK scheduling only – SWI & HWI continue unchanged Nestable - number of levels managed by BIOS 15 February 2018 Dr. Veton Këpuska 54

Disabling & Enabling Task Scheduling 15 February 2018 Dr. Veton Këpuska 55 TSK_disable (); // “critical section” ... // TSK scheduler inhibited ... TSK_enable ();

Modification of a Task’s Priority TSK_setpri () can raise or lower priority Return argument of TSK_setpri() is previous priority New priority remains until set again or TSK is deleted and re-created TSK priority is an integer value: 1 to 15 (unlike SWI, using binary weighted numbers)To suspend a TSK, set its priority to negative one (-1) Suspended TSK not part of BIOS TSK scheduling queueTSK can be activated at any time (by some other thread) via TSK_setpri () Handy option for statically created TSKs that don’t need to run right away A TSK can be suspended at any time under BIOS, by itself or another thread 15 February 2018 Dr. Veton Këpuska 56

Modification of a Task’s Priority Example 15 February 2018 Dr. Veton Këpuska 57 origPrio = TSK_setpri ( TSK_self (),7); // critical section ... // TSK priority increased or reduced ... TSK_setpri ( TSK_self (), origPrio );

TSK_yield : Time Slicing TSK_yield() instructs the BIOS scheduler to move the current TSK to the end of the priority queueIf another TSK of equal priority is ready, it will then be the active TSKThis API can be invoked at any time by the active TSK or any SWI/HWI If a PRD calls TSK_yield, time slicing amongst equal priority TSKs is achieved 15 February 2018 Dr. Veton Këpuska 58

TSK_yield : Time Slicing 15 February 2018 Dr. Veton Këpuska 59 TSK_D TSK_C TSK_B TSK_A Time Must be Equal Priority! Running Ready

TSK_sleep and TSK_tick TSK_sleep(Uns sleeptime ) Blocks execution of current TSK for n TSK ticks TSK_tick() Similar to PRD_tick for PRD SWIsAdvances the task alarm tick by one count Default - called from PRD_clock (system tick) If ‘ticks’ are events and not time, TSK_tick can be called from any thread TSK_itick () is for use inside ISRs w/o dispatcher 15 February 2018 Dr. Veton Këpuska 60

Task Control Block Model 15 February 2018 Dr. Veton Këpuska 61 READY RUNNING BLOCKED TERMINATED TSK_exit() TSK_sleep () TSK_tick () TSK_yield () BIOS Startup SEM_post() SEM_pend() TSK_setpri()

TSK Scheduler API 15 February 2018 Dr. Veton Këpuska 62 TSK API Description TSK_disable Disable DSP/BIOS task scheduler TSK_enable Enable DSP/BIOS task scheduler TSK_self Returns address of task object TSK_getpri Get task priority TSK_setpri Set a tasks execution priority TSK_yield Yield processor to equal priority task TSK_sleep Delay execution of the current task TSK_tick Advance system alarm clock TSK_itick Advance system alarm clock (ISR) TSK_time Return current value of system clock

Module Topics 15 February 2018 Dr. Veton Këpuska 63 3

Questions? 15 February 2018 Dr. Veton Këpuska 64

Module Topics 15 February 2018 Dr. Veton Këpuska 65 3

Lab Adding 2nd threaddummy load LED blinker CLK/PRD API to launch dummy threadUse some sched mgmt API to influence performance 15 February 2018 Dr. Veton Këpuska 66

Lab 7a: Multiple Threads 15 February 2018 Dr. Veton Këpuska 67 CLK – 100mS fxnLoad () read DIP sw’s call asm fn : load (load amt spec’d by sw values) Audio Out (48 KHz) ADC AIC33 Audio In (48 KHz) FIR.c FIR Code DAC AIC33 McBSP DXR udevCodec coeffs.c Coefficient s BIOS provided BIOS\Labs\Algos dioCodec IOM SIO PRD SWI fxnLoad() 3 2 DIP Sw’s: tskProcBuf procBuf while() SIO_reclaim (& sioIn ) for (i =0, i<HIST; i ++) pIn [i-HIST] = pPriorIn [ 2*BUF-HIST ]; if( sw0 == 1 ) FIR(in[ pIn -HIST ],out[ pOu t ]) else { pOut [i]= pIn [i]} C:\ dvsdk _1_01_00_15\ psp _1_00_02_00 McBSP DRR 00 none 10 low 01 hi 11 >100%

Lab 7a: Multiple Threads Begin with Lab 6 solutionAdd Load.c and NopLoop.asm (Algos dir ) to projectIn TCF file: set up CLK rate, create PRD SWI running at 100mSec rate, calling fxnLoadBuild , load, run; test audio w. range of DIP cases 15 February 2018 Dr. Veton Këpuska 68

Lab7b: Multiple Threads - Improved 15 February 2018 Dr. Veton Këpuska 69 CLK – 100mS fxnLoad () read DIP sw’s call asm fn : load (load amt spec’d by sw values) Audio Out (48 KHz) ADC AIC33 Audio In (48 KHz) FIR.c FIR Code DAC AIC33 McBSP DXR udevCodec coeffs.c Coefficient s BIOS provided BIOS\Labs\Algos dioCodec IOM SIO PRD SWI Function: _ SEM_post Arg0: _ mySem 3 2 DIP Sw’s: tskProcBuf procBuf while() SIO_reclaim (& sioIn ) for (i =0, i<HIST; i ++) pIn [i-HIST] = pPriorIn [ 2*BUF-HIST ]; if( sw0 == 1 ) FIR(in[ pIn -HIST ],out[ pOu t ]) else { pOut [i]= pIn [i]} C:\ dvsdk _1_01_00_15\ psp _1_00_02_00 McBSP DRR 00 none 10 low 01 hi 11 >100% TSK t skLoad () SEM_pend ( mySem ) callfxnLoad

Lab7b: Multiple Threads - Improved Have PRD SWI post SEMPut call to fxnLoad in TSK while loop Add SEM pend to TSK while loopCreate SEM for above signallingBuild , load, run; test audio w. range of DIP cases 15 February 2018 Dr. Veton Këpuska 70

Load.c void fxnLoad(void) { short i; unsigned char mask, dips; static Bool blink = 0; EVMDM6437_I2C_read( I2C_GPIO_GROUP_0, &dips, 1 ); if(hw_sw0 == (dips>>4&1)) { sw0 = hw_sw0 = !(dips>>4&1);} if(hw_sw1 == (dips>>5&1)) { sw1 = hw_sw1 = !(dips>>5&1);} if ( ( hw_sw2==(dips>>6&1)) | (hw_sw3== (dips>>7&1)) ){ sw2 = hw_sw2 = !(dips>>6&1); sw3 = hw_sw3 = !(dips>>7&1); } 15 February 2018 Dr. Veton Këpuska 71

Load.c switch(2*sw2+sw3){ case (3) : for (i=0; i< 7; i++){load(5000);} case (2) : for (i=0; i<12; i++){load(5000);} case (1) : load(5500); case (0) : load( 100); } blink^=1; mask = (char)( 0x0F^((1^blink)<<2*sw2+sw3) ); EVMDM6437_I2C_write( I2C_GPIO_GROUP_1, &mask, 1 ); IDL_run (); } 15 February 2018 Dr. Veton Këpuska 72

TI BIOS CLK-PRD END 15 February 2018 73 Dr. Veton Këpuska