;********************************************************************************************************
;                                               uC/CPU
;                                    CPU CONFIGURATION & PORT LAYER
;
;                    Copyright 2004-2020 Silicon Laboratories Inc. www.silabs.com
;
;                                 SPDX-License-Identifier: APACHE-2.0
;
;               This software is subject to an open source license and is distributed by
;                Silicon Laboratories Inc. pursuant to the terms of the Apache License,
;                    Version 2.0 available at www.apache.org/licenses/LICENSE-2.0.
;
;********************************************************************************************************

;********************************************************************************************************
;
;                                            CPU PORT FILE
;
;                                               ARMv7-M
;                                           ARM C Compiler
;
; Filename : cpu_a.asm
; Version  : v1.32.00
;********************************************************************************************************
; Note(s)  : This port supports the ARM Cortex-M3, Cortex-M4 and Cortex-M7 architectures.
;********************************************************************************************************


;********************************************************************************************************
;                                           PUBLIC FUNCTIONS
;********************************************************************************************************

        EXPORT  CPU_IntDis
        EXPORT  CPU_IntEn

        EXPORT  CPU_SR_Save
        EXPORT  CPU_SR_Restore

        EXPORT  CPU_WaitForInt
        EXPORT  CPU_WaitForExcept


        EXPORT  CPU_CntLeadZeros
        EXPORT  CPU_CntTrailZeros
        EXPORT  CPU_RevBits


;********************************************************************************************************
;                                      CODE GENERATION DIRECTIVES
;********************************************************************************************************

        AREA |.text|, CODE, READONLY, ALIGN=2
        THUMB
        REQUIRE8
        PRESERVE8

;********************************************************************************************************
;                                    DISABLE and ENABLE INTERRUPTS
;
; Description : Disable/Enable interrupts.
;
; Prototypes  : void  CPU_IntDis(void);
;               void  CPU_IntEn (void);
;********************************************************************************************************

CPU_IntDis
        CPSID   I
        BX      LR


CPU_IntEn
        CPSIE   I
        BX      LR


;********************************************************************************************************
;                                      CRITICAL SECTION FUNCTIONS
;
; Description : Disable/Enable Kernel aware interrupts by preserving the state of BASEPRI.  Generally speaking,
;               the state of the BASEPRI interrupt exception processing is stored in the local variable
;               'cpu_sr' & Kernel Aware interrupts are then disabled ('cpu_sr' is allocated in all functions
;               that need to disable Kernel aware interrupts). The previous BASEPRI interrupt state is restored
;               by copying 'cpu_sr' into the BASEPRI register.
;
; Prototypes  : CPU_SR  CPU_SR_Save   (CPU_SR  new_basepri);
;               void    CPU_SR_Restore(CPU_SR  cpu_sr);
;
; Note(s)     : (1) These functions are used in general like this :
;
;                       void  Task (void  *p_arg)
;                       {
;                           CPU_SR_ALLOC();                     /* Allocate storage for CPU status register */
;                               :
;                               :
;                           CPU_CRITICAL_ENTER();               /* cpu_sr = CPU_SR_Save();                  */
;                               :
;                               :
;                           CPU_CRITICAL_EXIT();                /* CPU_SR_Restore(cpu_sr);                  */
;                               :
;                       }
;
;               (2) Increasing priority using a write to BASEPRI does not take effect immediately.
;                   (a) IMPLICATION  This erratum means that the instruction after an MSR to boost BASEPRI
;                       might incorrectly be preempted by an insufficient high priority exception.
;
;                   (b) WORKAROUND  The MSR to boost BASEPRI can be replaced by the following code sequence:
;
;                       CPSID i
;                       MSR to BASEPRI
;                       DSB
;                       ISB
;                       CPSIE i
;********************************************************************************************************

CPU_SR_Save
        CPSID   I                               ; Cortex-M7 errata notice. See Note #2
        PUSH   {R1}
        MRS     R1, BASEPRI
        MSR     BASEPRI, R0
        DSB
        ISB
        MOV     R0, R1
        POP    {R1}
        CPSIE   I
        BX      LR


CPU_SR_Restore
        CPSID   I                               ; Cortex-M7 errata notice. See Note #2
        MSR     BASEPRI, R0
        DSB
        ISB
        CPSIE   I
        BX      LR


;********************************************************************************************************
;                                         WAIT FOR INTERRUPT
;
; Description : Enters sleep state, which will be exited when an interrupt is received.
;
; Prototypes  : void  CPU_WaitForInt (void)
;
; Argument(s) : none.
;********************************************************************************************************

CPU_WaitForInt
        WFI                                     ; Wait for interrupt
        BX      LR


;********************************************************************************************************
;                                         WAIT FOR EXCEPTION
;
; Description : Enters sleep state, which will be exited when an exception is received.
;
; Prototypes  : void  CPU_WaitForExcept (void)
;
; Argument(s) : none.
;********************************************************************************************************

CPU_WaitForExcept
        WFE                                     ; Wait for exception
        BX      LR


;********************************************************************************************************
;                                         CPU_CntLeadZeros()
;                                        COUNT LEADING ZEROS
;
; Description : Counts the number of contiguous, most-significant, leading zero bits before the
;                   first binary one bit in a data value.
;
; Prototype   : CPU_DATA  CPU_CntLeadZeros(CPU_DATA  val);
;
; Argument(s) : val         Data value to count leading zero bits.
;
; Return(s)   : Number of contiguous, most-significant, leading zero bits in 'val'.
;
; Note(s)     : (1) (a) Supports 32-bit data value size as configured by 'CPU_DATA' (see 'cpu.h
;                       CPU WORD CONFIGURATION  Note #1').
;
;                   (b) For 32-bit values :
;
;                             b31  b30  b29  ...  b04  b03  b02  b01  b00    # Leading Zeros
;                             ---  ---  ---       ---  ---  ---  ---  ---    ---------------
;                              1    x    x         x    x    x    x    x            0
;                              0    1    x         x    x    x    x    x            1
;                              0    0    1         x    x    x    x    x            2
;                              :    :    :         :    :    :    :    :            :
;                              :    :    :         :    :    :    :    :            :
;                              0    0    0         1    x    x    x    x           27
;                              0    0    0         0    1    x    x    x           28
;                              0    0    0         0    0    1    x    x           29
;                              0    0    0         0    0    0    1    x           30
;                              0    0    0         0    0    0    0    1           31
;                              0    0    0         0    0    0    0    0           32
;
;
;               (2) MUST be defined in 'cpu_a.asm' (or 'cpu_c.c') if CPU_CFG_LEAD_ZEROS_ASM_PRESENT is
;                   #define'd in 'cpu_cfg.h' or 'cpu.h'.
;********************************************************************************************************

CPU_CntLeadZeros
        CLZ     R0, R0                          ; Count leading zeros
        BX      LR


;********************************************************************************************************
;                                         CPU_CntTrailZeros()
;                                        COUNT TRAILING ZEROS
;
; Description : Counts the number of contiguous, least-significant, trailing zero bits before the
;                   first binary one bit in a data value.
;
; Prototype   : CPU_DATA  CPU_CntTrailZeros(CPU_DATA  val);
;
; Argument(s) : val         Data value to count trailing zero bits.
;
; Return(s)   : Number of contiguous, least-significant, trailing zero bits in 'val'.
;
; Note(s)     : (1) (a) Supports 32-bit data value size as configured by 'CPU_DATA' (see 'cpu.h
;                       CPU WORD CONFIGURATION  Note #1').
;
;                   (b) For 32-bit values :
;
;                             b31  b30  b29  b28  b27  ...  b02  b01  b00    # Trailing Zeros
;                             ---  ---  ---  ---  ---       ---  ---  ---    ----------------
;                              x    x    x    x    x         x    x    1            0
;                              x    x    x    x    x         x    1    0            1
;                              x    x    x    x    x         1    0    0            2
;                              :    :    :    :    :         :    :    :            :
;                              :    :    :    :    :         :    :    :            :
;                              x    x    x    x    1         0    0    0           27
;                              x    x    x    1    0         0    0    0           28
;                              x    x    1    0    0         0    0    0           29
;                              x    1    0    0    0         0    0    0           30
;                              1    0    0    0    0         0    0    0           31
;                              0    0    0    0    0         0    0    0           32
;
;
;               (2) MUST be defined in 'cpu_a.asm' (or 'cpu_c.c') if CPU_CFG_TRAIL_ZEROS_ASM_PRESENT is
;                   #define'd in 'cpu_cfg.h' or 'cpu.h'.
;********************************************************************************************************

CPU_CntTrailZeros
        RBIT    R0, R0                          ; Reverse bits
        CLZ     R0, R0                          ; Count trailing zeros
        BX      LR


;********************************************************************************************************
;                                            CPU_RevBits()
;                                            REVERSE BITS
;
; Description : Reverses the bits in a data value.
;
; Prototypes  : CPU_DATA  CPU_RevBits(CPU_DATA  val);
;
; Argument(s) : val         Data value to reverse bits.
;
; Return(s)   : Value with all bits in 'val' reversed (see Note #1).
;
; Note(s)     : (1) The final, reversed data value for 'val' is such that :
;
;                       'val's final bit  0       =  'val's original bit  N
;                       'val's final bit  1       =  'val's original bit (N - 1)
;                       'val's final bit  2       =  'val's original bit (N - 2)
;
;                               ...                           ...
;
;                       'val's final bit (N - 2)  =  'val's original bit  2
;                       'val's final bit (N - 1)  =  'val's original bit  1
;                       'val's final bit  N       =  'val's original bit  0
;********************************************************************************************************

CPU_RevBits
        RBIT    R0, R0                          ; Reverse bits
        BX      LR


;********************************************************************************************************
;                                     CPU ASSEMBLY PORT FILE END
;********************************************************************************************************

        END

