forked from Imagelibrary/rtems
66c50e281a
* cpu_supplement/arm.t, cpu_supplement/i386.t, cpu_supplement/m68k.t, cpu_supplement/mips.t, cpu_supplement/powerpc.t, cpu_supplement/sh.t, cpu_supplement/sparc.t, cpu_supplement/tic4x.t, porting/cpuinit.t, user/conf.t, user/init.t: Move interrupt_stack_size field from CPU Table to Configuration Table. Eliminate CPU Table from all ports. Delete references to CPU Table in all forms.
53 lines
1.7 KiB
Perl
53 lines
1.7 KiB
Perl
@c
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@c COPYRIGHT (c) 1988-2002.
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@c On-Line Applications Research Corporation (OAR).
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@c All rights reserved.
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@c
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@c $Id$
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@c
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@chapter CPU Initialization
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This section describes the general CPU and system initialization sequence
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as it pertains to the CPU dependent code.
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@section Introduction
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XXX general startup sequence description rewritten to make it more
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applicable to CPU depdent code in executive
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@section Initializing the CPU
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The _CPU_Initialize routine performs processor dependent initialization.
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@example
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void _CPU_Initialize(
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void (*thread_dispatch) /* may be ignored */
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)
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@end example
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The thread_dispatch argument is the address of the entry point for the
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routine called at the end of an ISR once it has been decided a context
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switch is necessary. On some compilation systems it is difficult to call
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a high-level language routine from assembly. Providing the address of the
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_Thread_ISR_Dispatch routine allows the porter an easy way to obtain this
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critical address and thus provides an easy way to work around this
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limitation on these systems.
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If you encounter this problem save the entry point in a CPU dependent
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variable as shown below:
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@example
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_CPU_Thread_dispatch_pointer = thread_dispatch;
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@end example
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During the initialization of the context for tasks with floating point,
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the CPU dependent code is responsible for initializing the floating point
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context. If there is not an easy way to initialize the FP context during
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Context_Initialize, then it is usually easier to save an "uninitialized"
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FP context here and copy it to the task's during Context_Initialize. If
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this technique is used to initialize the FP contexts, then it is important
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to ensure that the state of the floating point unit is in a coherent,
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initialized state.
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