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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           : ph.pdf
;*** Creation       : Wed Mar 11 09:58:34 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  : ph
;*** Document No.   : 6147.112.01.100
;*** Document Date  : 2001-10-26
;*** Document Status: APPROVED
;*** Document Author: SBK
;********************************************************************************



PRAGMA 	SRC_FILE_TIME 	"Thu Nov 29 09:50:28 2007"
PRAGMA 	LAST_MODIFIED 	"2001-10-26"
PRAGMA 	ID_AND_VERSION 	"6147.112.01.100"



CONST 	DUMMY_PH 	0 	; Dummy, not used, needed to satisfy tool chain which requires at least one constant definition in a SAP



VALTAB 	VAL_ch_type
VAL 	0 	CH_TYPE_SACCH 	"SACCH"
VAL 	1 	CH_TYPE_SDCCH 	"SDCCH"
VAL 	2 	CH_TYPE_FACCH 	"FACCH Full Rate"
VAL 	3 	 	"reserved"
VAL 	4 	 	"reserved"
VAL 	5 	 	"reserved"
VAL 	6 	 	"reserved"
VAL 	7 	CH_TYPE_FACCH_HR 	"FACCH Half Rate"




VAR 	l2_channel 	"Layer 2 channel-type" 	B

VAL 	@p_mphc - VAL_l2_channel@ 	

VAR 	l_buf 	"length of content in bit" 	S


VAR 	o_buf 	"offset of content in bit" 	S


VAR 	buf 	"buffer content; the actual size of buf is determined and allocated at run-time and not restricted to 1;" 	B


VAR 	dummy 	"dummy not used" 	B





COMP 	sdu 	 "message unit"
{
 	l_buf 	 ; length of content in bit
 	o_buf 	 ; offset of content in bit
 	buf 	[1] 	 ; buffer content; the actual size of buf is determined and allocated at run-time and not restricted to 1;
}






; PH_READY_TO_SEND 	0x4100
; PH_DATA_REQ 	0x0100
; PH_TRACE_IND 	0x4102



PRIM 	PH_READY_TO_SEND 	0x4100
{
 	l2_channel AS ch_type 	 ; channel type
}






PRIM 	PH_DATA_REQ 	0x0100
{
 	l2_channel AS ch_type 	 ; channel type
 	dummy 	 ; dummy not used; reserved
 	sdu 	 ; message unit
}






PRIM 	PH_TRACE_IND 	0x4102
{
 	dummy 	 ; dummy not used; not used
}