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/****************************************************************************
* arch/z80/src/z8/z8_saveirqcontext.c
*
* Copyright (C) 2008-2009 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <stdint.h>
#include <arch/irq.h>
#include "chip/switch.h"
#include "up_internal.h"
/****************************************************************************
* Definitions
****************************************************************************/
/****************************************************************************
* Private Data
****************************************************************************/
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: z8_saveirqcontext
*
* Description:
* In order to provide faster interrupt handling, the interrupt logic does
* "lazy" context saving as described below:
*
* (1) At the time of the interrupt, minimum information is saved and the
* register pointer is changed so that the interrupt logic does not
* alter the state of the interrupted task's registers.
* (2) If no context switch occurs during the interrupt processing, then
* the return from interrupt is also simple.
* (3) If a context switch occurs during interrupt processing, then
* (a) The full context of the interrupt task is saved, and
* (b) A full context switch is performed when the interrupt exits
* (see z8_vector.S).
*
* This function implements the full-context switch of bullet 3a.
*
****************************************************************************/
void z8_saveirqcontext(FAR chipreg_t *regs)
{
/* If we have already saved the interrupted task's registers in the TCB,
* then we do not need to do anything.
*/
if (g_z8irqstate.state == Z8_IRQSTATE_ENTRY)
{
/* Calculate the source address based on the saved RP value */
uint16_t rp = g_z8irqstate.regs[Z8_IRQSAVE_RPFLAGS] >> 8;
FAR chipreg_t *src = (FAR uint16_t*)(rp & 0xf0);
FAR chipreg_t *dest = ®s[XCPT_RR0];
/* Copy the interrupted tasks register into the TCB register save area. */
int i;
for (i = 0; i < XCPTCONTEXT_REGS; i++)
{
*dest++ = *src++;
}
/* Since the task was interrupted, we know that interrupts were enabled */
regs[XCPT_IRQCTL] = 0x0080; /* IRQE bit will enable interrupts */
/* The g_z8irqstate.regs pointer is the value of the stack pointer at
* the time that up_doirq() was called. Therefore, we can calculate
* the correct value for the stack pointer on return from interrupt:
*/
regs[XCPT_SP] = ((chipreg_t)g_z8irqstate.regs) + Z8_IRQSAVE_SIZE;
/* Copy the PC, RP, and FLAGS information from the lazy save to the TCB
* register save area.
*/
regs[XCPT_RPFLAGS] = g_z8irqstate.regs[Z8_IRQSAVE_RPFLAGS];
regs[XCPT_PC] = g_z8irqstate.regs[Z8_IRQSAVE_PC];
/* Now update the IRQ save area so that we will know that we have already
* done this.
*/
g_z8irqstate.state = Z8_IRQSTATE_SAVED;
g_z8irqstate.regs = regs;
}
}
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