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/****************************************************************************
* arch/mips/src/mips32/up_initialstate.c
*
* Copyright (C) 2011 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 <sys/types.h>
#include <stdint.h>
#include <string.h>
#include <nuttx/arch.h>
#include <arch/irq.h>
#include <arch/mips32/cp0.h>
#include "up_internal.h"
#include "up_arch.h"
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/****************************************************************************
* Private Data
****************************************************************************/
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: up_initial_state
*
* Description:
* A new thread is being started and a new TCB
* has been created. This function is called to initialize
* the processor specific portions of the new TCB.
*
* This function must setup the intial architecture registers
* and/or stack so that execution will begin at tcb->start
* on the next context switch.
*
****************************************************************************/
void up_initial_state(struct tcb_s *tcb)
{
struct xcptcontext *xcp = &tcb->xcp;
uint32_t regval;
/* Initialize the initial exception register context structure */
memset(xcp, 0, sizeof(struct xcptcontext));
/* Save the initial stack pointer. Hmmm.. the stack is set to the very
* beginning of the stack region. Some functions may want to store data on
* the caller's stack and it might be good to reserve some space. However,
* only the start function would do that and we have control over that one
*/
xcp->regs[REG_SP] = (uint32_t)tcb->adj_stack_ptr;
/* Save the task entry point */
xcp->regs[REG_EPC] = (uint32_t)tcb->start;
/* If this task is running PIC, then set the PIC base register to the
* address of the allocated D-Space region.
*/
#ifdef CONFIG_PIC
# warning "Missing logic"
#endif
/* Set privileged- or unprivileged-mode, depending on how NuttX is
* configured and what kind of thread is being started.
*
* If the kernel build is not selected, then all threads run in
* privileged thread mode.
*/
#ifdef CONFIG_NUTTX_KERNEL
# warning "Missing logic"
#endif
/* Set the initial value of the status register. It will be the same
* as the current status register with some changes:
*
* 1. Make sure the IE is set
* 2. Clear the BEV bit (This bit should already be clear)
* 3. Clear the UM bit so that the new task executes in kernel mode
* (This bit should already be clear)
* 4. Set the interrupt mask bits (depending on configuration)
* 5. Set the EXL bit (This will not be set)
*
* The EXL bit is set because this new STATUS register will be
* instantiated in kernel mode inside of an interrupt handler. EXL
* will be automatically cleared by the eret instruction.
*/
regval = cp0_getstatus();
#ifdef CONFIG_SUPPRESS_INTERRUPTS
regval &= ~(CP0_STATUS_IM_ALL | CP0_STATUS_BEV | CP0_STATUS_UM);
regval |= (CP0_STATUS_IE | CP0_STATUS_EXL | CP0_STATUS_IM_SWINTS);
#else
regval &= ~(CP0_STATUS_BEV | CP0_STATUS_UM);
regval |= (CP0_STATUS_IE | CP0_STATUS_EXL | CP0_STATUS_IM_ALL);
#endif
xcp->regs[REG_STATUS] = regval;
}
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