From 33cd2d43a18851aafdcb6bbdeebab679d8ab1c86 Mon Sep 17 00:00:00 2001 From: Joel Sherrill Date: Wed, 6 Oct 1999 19:36:28 +0000 Subject: New manual. First version to CVS. Just starting to see if it builds. --- doc/porting/cpuinit.t | 85 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 85 insertions(+) create mode 100644 doc/porting/cpuinit.t (limited to 'doc/porting/cpuinit.t') diff --git a/doc/porting/cpuinit.t b/doc/porting/cpuinit.t new file mode 100644 index 0000000000..49d9956249 --- /dev/null +++ b/doc/porting/cpuinit.t @@ -0,0 +1,85 @@ +@chapter CPU Initialization + +This section describes the general CPU and system initialization sequence +as it pertains to the CPU dependent code. + +@section Introduction + +XXX general startup sequence description rewritten to make it more +applicable to CPU depdent code in executive + +@section CPU Dependent Configuration Table + +The CPU Dependent Configuration Table contains information which tailors +the behavior of RTEMS base Some of the fields in this table are required +to be present in all ports of RTEMS. These fields appear at the beginning +of the data structure. Fields past this point may be CPU family and CPU +model dependent. For example, a port may add a field to specify the +default value for an interrupt mask register on the CPU. This table is +initialized by the Board Support Package and passed to the +rtems_initialize_executive or rtems_initialize_executive_early directive. + +@example +typedef struct @{ + void (*pretasking_hook)( void ); + void (*predriver_hook)( void ); + void (*postdriver_hook)( void ); + void (*idle_task)( void ); + boolean do_zero_of_workspace; + unsigned32 idle_task_stack_size; + unsigned32 interrupt_stack_size; + unsigned32 extra_mpci_receive_server_stack; + void * (*stack_allocate_hook)( unsigned32 ); + void (*stack_free_hook)( void* ); + /* end of fields required on all CPUs */ + + unsigned32 some_other_cpu_dependent_info; +@} rtems_cpu_table; +@end example + +XXX copy the descriptions of the fields from another CPU supplement + +@section Initializing the CPU + +The _CPU_Initialize routine performs processor dependent initialization. + +@example +void _CPU_Initialize( + rtems_cpu_table *cpu_table, + void (*thread_dispatch) /* may be ignored */ +) +@end example + +The thread_dispatch argument is the address of the entry point for the +routine called at the end of an ISR once it has been decided a context +switch is necessary. On some compilation systems it is difficult to call +a high-level language routine from assembly. Providing the address of the +_Thread_ISR_Dispatch routine allows the porter an easy way to obtain this +critical address and thus provides an easy way to work around this +limitation on these systems. + +If you encounter this problem save the entry point in a CPU dependent +variable as shown below: + +@example +_CPU_Thread_dispatch_pointer = thread_dispatch; +@end example + + +During the initialization of the context for tasks with floating point, +the CPU dependent code is responsible for initializing the floating point +context. If there is not an easy way to initialize the FP context during +Context_Initialize, then it is usually easier to save an "uninitialized" +FP context here and copy it to the task's during Context_Initialize. If +this technique is used to initialize the FP contexts, then it is important +to ensure that the state of the floating point unit is in a coherent, +initialized state. + +Finally, this routine is responsible for copying the application's CPU +Table into a locally accessible and modifiable area. This is shown below: + +@example +_CPU_Table = *cpu_table; +@end example + + -- cgit v1.2.3