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2008-06-02 Joel Sherrill <joel.sherrill@oarcorp.com>

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* user/bsp.t, user/init.t: Rework initialization and BSP chapters to
	account for changes to initialization framework.
This commit is contained in:
Joel Sherrill
2008-06-02 16:07:42 +00:00
parent 89ae273da7
commit a73e356164
3 changed files with 271 additions and 182 deletions
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5
doc/ChangeLog
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@@ -1,3 +1,8 @@
2008-06-02 Joel Sherrill <joel.sherrill@oarcorp.com>
* user/bsp.t, user/init.t: Rework initialization and BSP chapters to
account for changes to initialization framework.
2008-05-22 Joel Sherrill <joel.sherrill@OARcorp.com>
* user/conf.t: Add baseline interface for Watchdog Driver.

156
doc/user/bsp.t
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@@ -33,20 +33,9 @@ initialization code are highly processor and target dependent,
the logical functionality of these actions are similar across a
variety of processors and target platforms.
Normally, the application's initialization is
performed at two separate times: before the call to
@code{@value{DIRPREFIX}initialize_executive}
(reset application initialization) and
after @code{@value{DIRPREFIX}initialize_executive}
in the user's initialization tasks
(local and global application initialization). The order of the
startup procedure is as follows:
@enumerate
@item Reset application initialization.
@item Call to @code{@value{DIRPREFIX}initialize_executive}
@item Local and global application initialization.
@end enumerate
Normally, the BSP and some of the application initialization is
intertwined in the RTEMS initialization sequence controlled by
the shared function @code{boot_card()}.
The reset application initialization code is executed
first when the processor is reset. All of the hardware must be
@@ -57,49 +46,45 @@ application. Some of the hardware components may be initialized
in this code as well as any application initialization that does
not involve calls to RTEMS directives.
The processor's Interrupt Vector Table which will be
used by the application may need to be set to the required value
by the reset application initialization code. Because
interrupts are enabled automatically by RTEMS as part of the
@code{@value{DIRPREFIX}initialize_executive} directive,
the Interrupt Vector Table MUST
be set before this directive is invoked to ensure correct
interrupt vectoring. The processor's Interrupt Vector Table
must be accessible by RTEMS as it will be modified by the
@code{@value{DIRPREFIX}interrupt_catch} directive.
On some CPUs, RTEMS installs it's
own Interrupt Vector Table as part of initialization and thus
these requirements are met automatically. The reset code which
is executed before the call to @code{@value{DIRPREFIX}initialize_executive}
has the following requirements:
The processor's Interrupt Vector Table which will be used by the
application may need to be set to the required value by the reset
application initialization code. Because interrupts are enabled
automatically by RTEMS as part of the context switch to the first task,
the Interrupt Vector Table MUST be set before this directive is invoked
to ensure correct interrupt vectoring. The processor's Interrupt Vector
Table must be accessible by RTEMS as it will be modified by the when
installing user Interrupt Service Routines (ISRs) On some CPUs, RTEMS
installs it's own Interrupt Vector Table as part of initialization and
thus these requirements are met automatically. The reset code which is
executed before the call to any RTEMS initialization routines has the
following requirements:
@itemize @bullet
@item Must not make any RTEMS directive calls.
@item Must not make any blocking RTEMS directive calls.
@item If the processor supports multiple privilege levels,
must leave the processor in the most privileged, or supervisory,
state.
@item If the processor supports multiple privilege levels, must leave
the processor in the most privileged, or supervisory, state.
@item Must allocate a stack of at least @code{@value{RPREFIX}MINIMUM_STACK_SIZE}
bytes and initialize the stack pointer for the
@code{@value{DIRPREFIX}initialize_executive} directive.
bytes and initialize the stack pointer for the initialization process.
@item Must initialize the processor's Interrupt Vector Table.
@item Must disable all maskable interrupts.
@item If the processor supports a separate interrupt stack,
must allocate the interrupt stack and initialize the interrupt
stack pointer.
@item If the processor supports a separate interrupt stack, must allocate
the interrupt stack and initialize the interrupt stack pointer.
@end itemize
The @code{@value{DIRPREFIX}initialize_executive} directive does not return to
the initialization code, but causes the highest priority
initialization task to begin execution. Initialization tasks
are used to perform both local and global application
initialization which is dependent on RTEMS facilities. The user
initialization task facility is typically used to create the
application's set of tasks.
At the end of the initialization sequence, RTEMS does not return to the
BSP initialization code, but instead context switches to the highest
priority task to begin application execution. This task is typically
a User Initialization Task which is responsible for performing both
local and global application initialization which is dependent on RTEMS
facilities. It is also responsible for initializing any higher level
RTEMS services the application uses such as networking and blocking
device drivers.
@subsection Interrupt Stack Requirements
@@ -121,38 +106,36 @@ stack usage must account for the following requirements:
@item Application subroutine calls
@end itemize
The size of the interrupt stack must be greater than
or equal to the constant @code{@value{RPREFIX}MINIMUM_STACK_SIZE}.
The size of the interrupt stack must be greater than or equal to the
constant @code{@value{RPREFIX}MINIMUM_STACK_SIZE}.
@subsection Processors with a Separate Interrupt Stack
Some processors support a separate stack for
interrupts. When an interrupt is vectored and the interrupt is
not nested, the processor will automatically switch from the
current stack to the interrupt stack. The size of this stack is
based solely on the worst-case stack usage by interrupt service
routines.
Some processors support a separate stack for interrupts. When an
interrupt is vectored and the interrupt is not nested, the processor
will automatically switch from the current stack to the interrupt stack.
The size of this stack is based solely on the worst-case stack usage by
interrupt service routines.
The dedicated interrupt stack for the entire
application is supplied and initialized by the reset and
initialization code of the user's board support package. Since
all ISRs use this stack, the stack size must take into account
the worst case stack usage by any combination of nested ISRs.
The dedicated interrupt stack for the entire application on some
architectures is supplied and initialized by the reset and initialization
code of the user's Board Support Package. Whether allocated and
initialized by the BSP or RTEMS, since all ISRs use this stack, the
stack size must take into account the worst case stack usage by any
combination of nested ISRs.
@subsection Processors without a Separate Interrupt Stack
@subsection Processors Without a Separate Interrupt Stack
Some processors do not support a separate stack for
interrupts. In this case, without special assistance every
task's stack must include enough space to handle the task's
worst-case stack usage as well as the worst-case interrupt stack
usage. This is necessary because the worst-case interrupt
nesting could occur while any task is executing.
Some processors do not support a separate stack for interrupts. In this
case, without special assistance every task's stack must include
enough space to handle the task's worst-case stack usage as well as
the worst-case interrupt stack usage. This is necessary because the
worst-case interrupt nesting could occur while any task is executing.
On many processors without dedicated hardware managed
interrupt stacks, RTEMS manages a dedicated interrupt stack in
software. If this capability is supported on a CPU, then it is
logically equivalent to the processor supporting a separate
interrupt stack in hardware.
On many processors without dedicated hardware managed interrupt stacks,
RTEMS manages a dedicated interrupt stack in software. If this capability
is supported on a CPU, then it is logically equivalent to the processor
supporting a separate interrupt stack in hardware.
@section Device Drivers
@@ -178,23 +161,20 @@ the application is to utilize timeslicing, the clock manager, the
timer manager, the rate monotonic manager, or the timeout option on blocking
directives.
The clock tick is usually provided as an interrupt
from a counter/timer or a real-time clock device. When a
counter/timer is used to provide the clock tick, the device is
typically programmed to operate in continuous mode. This mode
selection causes the device to automatically reload the initial
count and continue the countdown without programmer
intervention. This reduces the overhead required to manipulate
the counter/timer in the clock tick ISR and increases the
accuracy of tick occurrences. The initial count can be based on
the microseconds_per_tick field in the RTEMS Configuration
Table. An alternate approach is to set the initial count for a
fixed time period (such as one millisecond) and have the ISR
invoke @code{@value{DIRPREFIX}clock_tick}
on the microseconds_per_tick boundaries.
Obviously, this can induce some error if the configured
microseconds_per_tick is not evenly divisible by the chosen
clock interrupt quantum.
The clock tick is usually provided as an interrupt from a counter/timer
or a real-time clock device. When a counter/timer is used to provide the
clock tick, the device is typically programmed to operate in continuous
mode. This mode selection causes the device to automatically reload the
initial count and continue the countdown without programmer intervention.
This reduces the overhead required to manipulate the counter/timer in
the clock tick ISR and increases the accuracy of tick occurrences.
The initial count can be based on the microseconds_per_tick field
in the RTEMS Configuration Table. An alternate approach is to set
the initial count for a fixed time period (such as one millisecond)
and have the ISR invoke @code{@value{DIRPREFIX}clock_tick} on the
configured @code{microseconds_per_tick} boundaries. Obviously, this
can induce some error if the configured @code{microseconds_per_tick}
is not evenly divisible by the chosen clock interrupt quantum.
It is important to note that the interval between
clock ticks directly impacts the granularity of RTEMS timing
@@ -235,7 +215,7 @@ switch extension would save and restore the context of the
device.
For more information on user extensions, refer to the
User Extensions chapter.
@ref{User Extensions Manager} chapter.
@section Multiprocessor Communications Interface (MPCI)

292
doc/user/init.t
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@@ -10,17 +10,19 @@
@section Introduction
The initialization manager is responsible for
The Initialization Manager is responsible for
initiating and shutting down RTEMS. Initiating RTEMS involves
creating and starting all configured initialization tasks, and
for invoking the initialization routine for each user-supplied
device driver. In a multiprocessor configuration, this manager
also initializes the interprocessor communications layer. The
directives provided by the initialization manager are:
directives provided by the Initialization Manager are:
@itemize @bullet
@item @code{@value{DIRPREFIX}initialize_executive_early} - Initialize RTEMS and do NOT Start Multitasking
@item @code{@value{DIRPREFIX}initialize_executive_late} - Complete Initialization and Start Multitasking
@item @code{@value{DIRPREFIX}initialize_data_structures} - Initialize RTEMS Data Structures
@item @code{@value{DIRPREFIX}initialize_before_drivers} - Perform Initialization Before Device Drivers
@item @code{@value{DIRPREFIX}initialize_device_drivers} - Initialize Device Drivers
@item @code{@value{DIRPREFIX}initialize_start_multitasking} - Complete Initialization and Start Multitasking
@item @code{@value{DIRPREFIX}shutdown_executive} - Shutdown RTEMS
@end itemize
@@ -53,41 +55,40 @@ This transformation typically involves changing priority and
execution mode. RTEMS does not automatically delete the
initialization tasks.
@subsection The System Initialization Task
@subsection System Initialization
The System Initialization Task is responsible for
initializing all device drivers. As a result, this task has a
higher priority than all other tasks to ensure that no
application tasks executes until all device drivers are
initialized. After device initialization in a single processor
system, this task will delete itself.
System Initialization begins with board reset and continues
through RTEMS initialization, initialization of all device
drivers, and eventually a context switch to the first user
task. Remember, that interrupts are disabled during
initialization and the @i{initialization thread} is not
a task in any sense and the user should be very careful
during initialzation.
The System Initialization Task must have enough stack
space to successfully execute the initialization routines for
The BSP must ensure that the there is enough stack
space reserved for the initialization "thread" to
successfully execute the initialization routines for
all device drivers and, in multiprocessor configurations, the
Multiprocessor Communications Interface Layer initialization
routine. The CPU Configuration Table contains a field which
allows the application or BSP to increase the default amount of
stack space allocated for this task.
In multiprocessor configurations, the System
Initialization Task does not delete itself after initializing
the device drivers. Instead it transforms itself into the
Multiprocessing Server which initializes the Multiprocessor
Communications Interface Layer, verifies multiprocessor system
consistency, and processes all requests from remote nodes.
routine.
@subsection The Idle Task
The Idle Task is the lowest priority task in a system
and executes only when no other task is ready to execute. This
task consists of an infinite loop and will be preempted when any
other task is made ready to execute.
default implementation of this task consists of an infinite
loop. RTEMS allows the Idle Task body to be replaced by a CPU
specific implementation, a BSP specific implementation or an
application specific implementation.
The Idle Task is preemptible and @b{WILL} be preempted when
any other task is made ready to execute. This characteristic is
critical to the overall behavior of any application.
@subsection Initialization Manager Failure
The @code{@value{DIRPREFIX}ifatal_error_occurred} directive will be called
from @code{@value{DIRPREFIX}initialize_executive}
The @code{@value{DIRPREFIX}fatal_error_occurred} directive will
be invoked from @code{@value{DIRPREFIX}initialize_executive}
for any of the following reasons:
@itemize @bullet
@@ -118,42 +119,72 @@ initialization sequence.
@item If any of the user initialization tasks cannot be
created or started successfully.
@end itemize
A discussion of RTEMS actions when a fatal error occurs
may be found @ref{Fatal Error Manager Announcing a Fatal Error}.
@section Operations
@subsection Initializing RTEMS
The Initializatiton Manager directives are called by the
board support package framework as part of its initialization
sequence. RTEMS assumes that the board support package
The Initialization Manager directives are called by the
Board Support Package framework as part of its initialization
sequence. RTEMS assumes that the Board Support Package
successfully completed its initialization activities. These
directives initialize RTEMS by performing the following actions:
@itemize @bullet
@item Initializing internal RTEMS variables;
@item Allocating system resources;
@item Creating and starting the System Initialization Task;
@item Creating and starting the Idle Task;
@item Initialize all device drivers;
@item Creating and starting the user initialization task(s); and
@item Initiating multitasking.
@end itemize
This directive MUST be called before any other RTEMS
directives. The effect of calling any RTEMS directives before
@code{@value{DIRPREFIX}initialize_executive_early}
is unpredictable. Many of RTEMS actions
during initialization are based upon the contents of the
Configuration Table. For more information regarding the format
and contents of this table, please refer to the chapter
Configuring a System.
The initialization directives MUST be called in the proper
sequence before any blocking directives may be used. The services
in this manager should be invoked just once per application
and in precisely the following order:
@itemize @bullet
@item @code{@value{DIRPREFIX}initialize_data_structures}
@item @code{@value{DIRPREFIX}initialize_before_drivers}
@item @code{@value{DIRPREFIX}initialize_device_drivers}
@item @code{@value{DIRPREFIX}initialize_start_multitasking}
@end itemize
It is recommended that the Board Support Package use the
provided framework which will invoke these services as
part of the executing the function @code{boot_card} in the
file @code{c/src/lib/libbsp/shared/bootcard.c}. This
framework will also assist in allocating memory to the
RTEMS Workspace and C Program Heap and initializing the
C Library.
The effect of calling any blocking RTEMS directives before
@code{@value{DIRPREFIX}initialize_start_multitasking}
is unpredictable but guaranteed to be bad. Afer the
directive @code{@value{DIRPREFIX}initialize_data_structures}
is invoked, it is permissible to allocate RTEMS objects and
perform non-blocking operations. But the user should be
distinctly aware that multitasking is not available yet
and they are @b{NOT} executing in a task context.
Many of RTEMS actions during initialization are based upon
the contents of the Configuration Table. For more information
regarding the format and contents of this table, please refer
to the chapter @ref{Configuring a System}.
The final step in the initialization sequence is the
initiation of multitasking. When the scheduler and dispatcher
are enabled, the highest priority, ready task will be dispatched
to run. Control will not be returned to the board support
package after multitasking is enabled until
@code{@value{DIRPREFIX}shutdown_executive_late}
the directive is called.
to run. Control will not be returned to the Board Support
Package after multitasking is enabled until the
@code{@value{DIRPREFIX}shutdown_executive} directive is called.
This directive is called as a side-effect of POSIX calls
including @code{exit}.
@subsection Shutting Down RTEMS
@@ -161,26 +192,26 @@ The @code{@value{DIRPREFIX}shutdown_executive} directive is invoked by the
application to end multitasking and return control to the board
support package. The board support package resumes execution at
the code immediately following the invocation of the
@code{@value{DIRPREFIX}initialize_executive} directive.
@code{@value{DIRPREFIX}initialize_start_multitasking} directive.
@section Directives
This section details the initialization manager's
This section details the Initialization Manager's
directives. A subsection is dedicated to each of this manager's
directives and describes the calling sequence, related
constants, usage, and status codes.
@page
@subsection INITIALIZE_EXECUTIVE_EARLY - Initialize RTEMS and do NOT Start Multitasking
@subsection INITIALIZE_DATA_STRUCTURES - Initialize RTEMS Data Structures
@cindex initialize RTEMS
@cindex initialize RTEMS data structures
@subheading CALLING SEQUENCE:
@ifset is-C
@findex rtems_initialize_executive_early
@findex rtems_initialize_data_structures
@example
rtems_interrupt_level rtems_initialize_executive_early(
void rtems_initialize_data_structures(
rtems_configuration_table *configuration_table
);
@end example
@@ -198,42 +229,36 @@ NONE
@subheading DESCRIPTION:
This directive is called when the board support
package has completed its initialization to allow RTEMS to
initialize the application environment based upon the
information in the Configuration Table, CPU Dependent
Information Table, User Initialization Tasks Table, Device
Driver Table, User Extension Table, Multiprocessor Configuration
Table, and the Multiprocessor Communications Interface (MPCI)
Table. This directive returns to the caller after completing
the basic RTEMS initialization but before multitasking is
initiated. The interrupt level in place when the directive is
invoked is returned to the caller. This interrupt level should
be the same one passed to
@code{@value{DIRPREFIX}initialize_executive_late}.
This directive is called when the Board Support
Package has completed its basic initialization and
allows RTEMS to initialize the application environment based upon the
information in the Configuration Table, User Initialization
Tasks Table, Device Driver Table, User Extension Table,
Multiprocessor Configuration Table, and the Multiprocessor
Communications Interface (MPCI) Table. This directive returns
to the caller after completing the basic RTEMS initialization.
@subheading NOTES:
The application must use only one of the two
initialization sequences:
@code{@value{DIRPREFIX}initialize_executive} or
@code{@value{DIRPREFIX}initialize_executive_early} and
@code{@value{DIRPREFIX}initialize_executive_late}.
The Initialization Manager directives must be used in the
proper sequence and invokved only once in the life of an application.
This directive must be invoked with interrupts disabled.
Interrupts should be disabled as early as possible in
the initialization sequence and remain disabled until
the first context switch.
@page
@subsection INITIALIZE_EXECUTIVE_LATE - Complete Initialization and Start Multitasking
@subsection INITIALIZE_BEFORE_DRIVERS - Perform Initialization Before Device Drivers
@cindex initialize RTEMS
@cindex start multitasking
@cindex initialize RTEMS before device drivers
@subheading CALLING SEQUENCE:
@ifset is-C
@findex rtems_initialize_executive_late
@findex rtems_initialize_before_drivers
@example
void rtems_initialize_executive_late(
rtems_interrupt_level bsp_level
);
void rtems_initialize_before_drivers(void);
@end example
@end ifset
@@ -249,21 +274,108 @@ NONE
@subheading DESCRIPTION:
This directive is called after the
@code{@value{DIRPREFIX}initialize_executive_early}
directive has been called to complete
the RTEMS initialization sequence and initiate multitasking.
The interrupt level returned by the
@code{@value{DIRPREFIX}initialize_executive_early}
directive should be in bsp_level and this value is restored as
part of this directive returning to the caller after the
@code{@value{DIRPREFIX}shutdown_executive}
directive is invoked.
This directive is called by the Board Support Package as the
second step in initializing RTEMS. This directive performs
initialization that must occur between basis RTEMS data structure
initialization and device driver initialization. In particular,
in a multiprocessor configuration, this directive will create the
MPCI Server Task. This directive returns to the caller after
completing the basic RTEMS initialization.
@subheading NOTES:
This directive MUST be the second RTEMS directive
called and it DOES NOT RETURN to the caller until the
The Initialization Manager directives must be used in the
proper sequence and invokved only once in the life of an application.
This directive must be invoked with interrupts disabled.
Interrupts should be disabled as early as possible in
the initialization sequence and remain disabled until
the first context switch.
@page
@subsection INITIALIZE_DEVICE_DRIVERS - Initialize Device Drivers
@cindex initialize device drivers
@subheading CALLING SEQUENCE:
@ifset is-C
@findex rtems_initialize_device_drivers
@example
void rtems_initialize_device_drivers(void);
@end example
@end ifset
@ifset is-Ada
@example
NOT SUPPORTED FROM Ada BINDING
@end example
@end ifset
@subheading DIRECTIVE STATUS CODES:
NONE
@subheading DESCRIPTION:
This directive is called by the Board Support Package as the
third step in initializing RTEMS. This directive initializes
all statically configured device drivers and performs all RTEMS
initialization which requires device drivers to be initialized.
In a multiprocessor configuration, this service will initialize
the Multiprocessor Communications Interface (MPCI) and synchronize
with the other nodes in the system.
After this directive is executed, control will be returned to
the Board Support Package framework.
@subheading NOTES:
The Initialization Manager directives must be used in the
proper sequence and invokved only once in the life of an application.
This directive must be invoked with interrupts disabled.
Interrupts should be disabled as early as possible in
the initialization sequence and remain disabled until
the first context switch.
@page
@subsection INITIALIZE_START_MULTITASKING - Complete Initialization and Start Multitasking
@cindex initialize RTEMS
@cindex start multitasking
@subheading CALLING SEQUENCE:
@ifset is-C
@findex rtems_initialize_start_multitasking
@example
void rtems_initialize_start_multitasking(void);
@end example
@end ifset
@ifset is-Ada
@example
NOT SUPPORTED FROM Ada BINDING
@end example
@end ifset
@subheading DIRECTIVE STATUS CODES:
NONE
@subheading DESCRIPTION:
This directive is called after the other Initialization Manager
directives have successfully completed. This directive
initiates multitasking and performs a context switch to
the first user application task and enables interrupts as
a side-effect of that context switch.
@subheading NOTES:
This directive @b{DOES NOT RETURN} to the caller until the
@code{@value{DIRPREFIX}shutdown_executive} is invoked.
This directive causes all nodes in the system to
@@ -271,14 +383,6 @@ verify that certain configuration parameters are the same as
those of the local node. If an inconsistency is detected, then
a fatal error is generated.
The application must use only one of the two
initialization sequences:
@code{@value{DIRPREFIX}initialize_executive} or
@code{@value{DIRPREFIX}initialize_executive_early} and
@code{@value{DIRPREFIX}initialize_executive_late}.
@page
@subsection SHUTDOWN_EXECUTIVE - Shutdown RTEMS