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ABB semaphore protection overhaul The ABB semaphone protection logic that came with TCS211 from TI was broken in several ways: * Some semaphore-protected functions were called from Application_Initialize() context. NU_Obtain_Semaphore() called with NU_SUSPEND fails with NU_INVALID_SUSPEND in this context, but the return value wasn't checked, and NU_Release_Semaphore() would be called unconditionally at the end. The latter call would increment the semaphore count past 1, making the semaphore no longer binary and thus no longer effective for resource protection. The fix is to check the return value from NU_Obtain_Semaphore() and skip the NU_Release_Semaphore() call if the semaphore wasn't properly obtained. * Some SPI hardware manipulation was being done before entering the semaphore- protected critical section. The fix is to reorder the code: first obtain the semaphore, then do everything else. * In the corner case of L1/DSP recovery, l1_abb_power_on() would call some non-semaphore-protected ABB & SPI init functions. The fix is to skip those calls in the case of recovery. * A few additional corner cases existed, all of which are fixed by making ABB semaphore protection 100% consistent for all ABB functions and code paths. There is still one remaining problem of priority inversion: suppose a low- priority task calls an ABB function, and some medium-priority task just happens to preempt right in the middle of that semaphore-protected ABB operation. Then the high-priority SPI task is locked out for a non-deterministic time until that medium-priority task finishes its work and goes back to sleep. This priority inversion problem remains outstanding for now.
author Mychaela Falconia <falcon@freecalypso.org>
date Mon, 26 Apr 2021 20:55:25 +0000
parents 35f7a1dc9f7d
children
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;********************************************************************************
;*** File           : mmss.pdf
;*** Creation       : Wed Mar 11 09:58:23 CST 2009
;*** XSLT Processor : Apache Software Foundation / http://xml.apache.org/xalan-j / supports XSLT-Ver: 1
;*** Copyright      : (c) Texas Instruments AG, Berlin Germany 2002
;********************************************************************************
;*** Document Type  : Service Access Point Specification
;*** Document Name  : mmss
;*** Document No.   : 6147.105.97.102
;*** Document Date  : 2002-07-19
;*** Document Status: BEING_PROCESSED
;*** Document Author: HM
;********************************************************************************



PRAGMA 	SRC_FILE_TIME 	"Thu Nov 29 09:47:24 2007"
PRAGMA 	LAST_MODIFIED 	"2002-07-19"
PRAGMA 	ID_AND_VERSION 	"6147.105.97.102"



CONST 	MAX_SDU_LEN 	1 	; maximum service data unit length



VALTAB 	VAL_ti
VAL 	0 - 6 	"ms originated transaction"
VAL 	8 - 14 	"ms originated transaction"
VAL 	7 	TI_RES_MO 	"reserved"
VAL 	15 	TI_RES_MT 	"reserved"




VAR 	cause 	"MM cause" 	S


VAR 	l_buf 	"length in bits" 	S


VAR 	o_buf 	"offset in bits" 	S


VAR 	buf 	"bit buffer" 	B


VAR 	ti 	"transaction identifier" 	B

VAL 	@p_mmss - VAL_ti@ 	

VAR 	d1 	"dummy, not used" 	B


VAR 	d2 	"dummy, not used" 	B





COMP 	sdu 	 "Service Data Unit"
{
 	l_buf 	 ; length in bits
 	o_buf 	 ; offset in bits
 	buf 	[MAX_SDU_LEN] 	 ; bit buffer
}






; MMSS_ESTABLISH_REQ 	0x80000008
; MMSS_RELEASE_REQ 	0x80010008
; MMSS_DATA_REQ 	0x80020008
; MMSS_DATA_IND 	0x80004008
; MMSS_ERROR_IND 	0x80014008
; MMSS_ESTABLISH_CNF 	0x80024008
; MMSS_ESTABLISH_IND 	0x80034008
; MMSS_RELEASE_IND 	0x80044008



PRIM 	MMSS_ESTABLISH_REQ 	0x80000008
{
 	ti 	 ; transaction identifier
}






PRIM 	MMSS_RELEASE_REQ 	0x80010008
{
 	ti 	 ; transaction identifier
}






PRIM 	MMSS_DATA_REQ 	0x80020008
{
 	d1 	 ; dummy
 	d2 	 ; dummy
 	sdu 	 ; service data unit
}






PRIM 	MMSS_DATA_IND 	0x80004008
{
 	d1 	 ; dummy
 	d2 	 ; dummy
 	sdu 	 ; service data unit
}






PRIM 	MMSS_ERROR_IND 	0x80014008
{
 	ti 	 ; transaction identifier
 	cause 	 ; error cause
}






PRIM 	MMSS_ESTABLISH_CNF 	0x80024008
{
 	ti 	 ; transaction identifier
}






PRIM 	MMSS_ESTABLISH_IND 	0x80034008
{
 	d1 	 ; dummy
 	d2 	 ; dummy
 	sdu 	 ; service data unit
}






PRIM 	MMSS_RELEASE_IND 	0x80044008
{
 	ti 	 ; transaction identifier
 	cause 	 ; release cause
}