/**************************************************************************
* up_restorecontext.c
*
* Copyright (C) 2007, 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 <nuttx/irq.h>
#include "up_internal.h"
/**************************************************************************
* Private Definitions
**************************************************************************/
/**************************************************************************
* Private Types
**************************************************************************/
/**************************************************************************
* Private Function Prototypes
**************************************************************************/
/**************************************************************************
* Global Variables
**************************************************************************/
/**************************************************************************
* Private Variables
**************************************************************************/
/**************************************************************************
* Private Functions
**************************************************************************/
/**************************************************************************
* Public Functions
**************************************************************************/
/**************************************************************************
* Name: up_restoreregisters
*
* Description:
* Restore the saved registers from the context save area. This function
* is called from up_restorecontext (below) and also from interrupt
* handling logic.
*
* Note that this function does not restore:
* a, dptr, ie - these are saved in the stack area
* sp - this can be inferred from g_irqtos or struct xcptontext.nbytes.
*
* Inputs:
* context - the context register array from which to restore the
* register values
*
* Return:
* None
*
**************************************************************************/
void up_restoreregisters(FAR uint8_t *regs) _naked
{
_asm
movx a, @dptr
mov b, a
inc dptr
movx a, @dptr
mov r2, a
inc dptr
movx a, @dptr
mov r3, a
inc dptr
movx a, @dptr
mov r4, a
inc dptr
movx a, @dptr
mov r5, a
inc dptr
movx a, @dptr
mov r6, a
inc dptr
movx a, @dptr
mov r7, a
inc dptr
movx a, @dptr
mov r0, a
inc dptr
movx a, @dptr
mov r1, a
inc dptr
movx a, @dptr
mov psw, a
inc dptr
movx a, @dptr
mov _bp, a
ret
_endasm;
}
/**************************************************************************
* Name: up_restorecontext
*
* Description:
* Restore the stack specified in the context structure and return to
* that context
*
* Inputs:
* context - Holds the stack content of the context to return to
*
* Return:
* This function does not return.
*
**************************************************************************/
void up_restorecontext(FAR struct xcptcontext *context) __naked
{
_asm
ar2 = 0x02
ar3 = 0x03
ar4 = 0x04
ar5 = 0x05
ar6 = 0x06
ar7 = 0x07
ar0 = 0x00
ar1 = 0x01
/* Dump the contents of the saved frame before it is copied back
* to memory/registers.
*/
#ifdef CONFIG_SWITCH_FRAME_DUMP
push dpl
push dph
lcall _up_dumpframe
pop dph
pop dpl
#endif
/* Interrupts should be disabled for the following. up_popcontext() will
* set the new interrupt state correctly.
*/
clr ea
/* The following logic will copy the stack from the
* context save structure into IRAM. We cannot use
* the stack in anyway during this copy. Instead,
* we will use registers as follows:
*
* R0 - Holds the working 8-bit IRAM pointer
* R1 - Not used
* R2-3 - Holds the working 16-bit XRAM pointer
* R4 - Holds the working byte count
* R5 - Holds the new stack pointer
* R6-7 - Saved context pointer
*/
/* Fetch r4 = context->nbytes */
movx a, @dptr
mov r4, a
/* Save the new stack pointer in r5 */
add a, #(STACK_BASE-1)
mov r5, a
/* Save r2-3 and r6-r7 = &context->stack */
inc dptr
mov r2, dpl
mov r3, dph
mov r6, dpl
mov r7, dph
/* Set r0 = stack base address */
mov r0, #STACK_BASE
/* Top of the copy loop -- we cannot use the stack
* again until we finish the copy and set the new
* stack pointer (saved in r5)
*/
00001$:
mov a, r4 /* a = bytes left to transfer */
dec r4 /* (for next time through the loop) */
jz 00002$ /* Jump if a = 0 (done) */
/* Fetch the next byte from context->stack */
mov dpl, r2
mov dph, r3
movx a, @dptr
/* Increment the XRAM pointer */
inc dptr
mov r2, dpl
mov r3, dph
/* Save the next byte into IRAM */
mov @r0, a
/* Increment the IRAM pointer */
inc r0
sjmp 00001$
00002$:
/* Set the new stack pointer and recover the
* context->stack pointer.
*/
mov sp, r5
mov dpl, r6
mov dph, r7
/* Dump the stack contents after they have
* been restored to IRAM
*/
#ifdef CONFIG_SWITCH_FRAME_DUMP
push dpl
push dph
lcall _up_dumpstack
pop dph
pop dpl
#endif
/* Get the pointer to the register save area */
mov a, #STACK_SIZE
add a, dpl
mov dpl, a
clr a
addc a, dph
mov dph, a
/* Restore registers from the register save area */
lcall _up_restoreregisters
/* Restore registers from the new stack */
pop dph
pop dpl
/* Restore the interrupt state per the stored IE value */
pop acc
jb acc.7,00003$
clr ie.7
sjmp 00004$
00003$:
setb ie.7
00004$:
pop acc
ret
_endasm;
}
