/* * Copyright (c) 2014 Wind River Systems, Inc. * * SPDX-License-Identifier: Apache-2.0 */ /** * @file * @brief Handling of transitions to-and-from fast IRQs (FIRQ) * * This module implements the code for handling entry to and exit from Fast IRQs. * * See isr_wrapper.S for details. */ #include #include #include #include #include #include GTEXT(_firq_enter) GTEXT(_firq_exit) /** * * @brief Work to be done before handing control to a FIRQ ISR * * The processor switches to a second register bank so registers from the * current bank do not have to be preserved yet. The only issue is the LP_START/ * LP_COUNT/LP_END registers, which are not banked. These can be saved * in available callee saved registers. * * If all FIRQ ISRs are programmed such that there are no use of the LP * registers (ie. no LPcc instruction), and CONFIG_ARC_STACK_CHECKING is * not set, then the kernel can be configured to not save and restore them. * * When entering a FIRQ, interrupts might as well be locked: the processor is * running at its highest priority, and cannot be interrupted by any other * interrupt. An exception, however, can be taken. * * Assumption by _isr_demux: r3 is untouched by _firq_enter. * * @return N/A */ SECTION_FUNC(TEXT, _firq_enter) /* * ATTENTION: * If CONFIG_RGF_NUM_BANKS>1, firq uses a 2nd register bank so GPRs do * not need to be saved. * If CONFIG_RGF_NUM_BANKS==1, firq must use the stack to save registers. * This has already been done by _isr_wrapper. */ #ifdef CONFIG_ARC_STACK_CHECKING #ifdef CONFIG_ARC_SECURE_FIRMWARE lr r2, [_ARC_V2_SEC_STAT] bclr r2, r2, _ARC_V2_SEC_STAT_SSC_BIT sflag r2 #else /* disable stack checking */ lr r2, [_ARC_V2_STATUS32] bclr r2, r2, _ARC_V2_STATUS32_SC_BIT kflag r2 #endif #endif #if CONFIG_RGF_NUM_BANKS != 1 /* * Save LP_START/LP_COUNT/LP_END because called handler might use. * Save these in callee saved registers to avoid using memory. * These will be saved by the compiler if it needs to spill them. */ mov r23,lp_count lr r24, [_ARC_V2_LP_START] lr r25, [_ARC_V2_LP_END] #endif /* check whether irq stack is used */ _check_and_inc_int_nest_counter r0, r1 bne.d firq_nest mov_s r0, sp _get_curr_cpu_irq_stack sp #if CONFIG_RGF_NUM_BANKS != 1 b firq_nest_1 firq_nest: /* * because firq and rirq share the same interrupt stack, * switch back to original register bank to get correct sp. * to get better firq latency, an approach is to prepare * separate interrupt stack for firq and do not do thread * switch in firq. */ lr r1, [_ARC_V2_STATUS32] and r1, r1, ~_ARC_V2_STATUS32_RB(7) kflag r1 /* here use _ARC_V2_USER_SP and ilink to exchange sp * save original value of _ARC_V2_USER_SP and ilink into * the stack of interrupted context first, then restore them later */ push ilink PUSHAX ilink, _ARC_V2_USER_SP /* sp here is the sp of interrupted context */ sr sp, [_ARC_V2_USER_SP] /* here, bank 0 sp must go back to the value before push and * PUSHAX as we will switch to bank1, the pop and POPAX later will * change bank1's sp, not bank0's sp */ add sp, sp, 8 /* switch back to banked reg, only ilink can be used */ lr ilink, [_ARC_V2_STATUS32] or ilink, ilink, _ARC_V2_STATUS32_RB(1) kflag ilink lr sp, [_ARC_V2_USER_SP] POPAX ilink, _ARC_V2_USER_SP pop ilink firq_nest_1: #else firq_nest: #endif push_s r0 j @_isr_demux /** * * @brief Work to be done exiting a FIRQ * * @return N/A */ SECTION_FUNC(TEXT, _firq_exit) #if CONFIG_RGF_NUM_BANKS != 1 /* restore lp_count, lp_start, lp_end from r23-r25 */ mov lp_count,r23 sr r24, [_ARC_V2_LP_START] sr r25, [_ARC_V2_LP_END] #endif _dec_int_nest_counter r0, r1 _check_nest_int_by_irq_act r0, r1 jne _firq_no_switch /* sp is struct k_thread **old of z_arc_switch_in_isr * which is a wrapper of z_get_next_switch_handle. * r0 contains the 1st thread in ready queue. if * it equals _current(r2) ,then do swap, or no swap. */ _get_next_switch_handle /* restore interrupted context' sp */ pop sp cmp r0, r2 bne _firq_switch /* fall to no switch */ .balign 4 _firq_no_switch: /* * Keeping this code block close to those that use it allows using brxx * instruction instead of a pair of cmp and bxx */ #if CONFIG_RGF_NUM_BANKS == 1 _pop_irq_stack_frame #endif rtie .balign 4 _firq_switch: #if CONFIG_RGF_NUM_BANKS != 1 /* * save r0, r2 in irq stack for a while, as they will be changed by register * bank switch */ _get_curr_cpu_irq_stack r1 st r0, [r1, -4] st r2, [r1, -8] /* * We know there is no interrupted interrupt of lower priority at this * point, so when switching back to register bank 0, it will contain the * registers from the interrupted thread. */ #if defined(CONFIG_USERSPACE) /* when USERSPACE is configured, here need to consider the case where firq comes * out in user mode, according to ARCv2 ISA and nsim, the following micro ops * will be executed: * sp<-reg bank1'sp * switch between sp and _ARC_V2_USER_SP * then: * sp is the sp of kernel stack of interrupted thread * _ARC_V2_USER_SP is reg bank1'sp * the sp of user stack of interrupted thread is reg bank0'sp * if firq comes out in kernel mode, the following micro ops will be executed: * sp<-reg bank'sp * so, sw needs to do necessary handling to set up the correct sp */ lr r0, [_ARC_V2_AUX_IRQ_ACT] bbit0 r0, 31, _firq_from_kernel aex sp, [_ARC_V2_USER_SP] lr r0, [_ARC_V2_STATUS32] and r0, r0, ~_ARC_V2_STATUS32_RB(7) kflag r0 aex sp, [_ARC_V2_USER_SP] b _firq_create_irq_stack_frame _firq_from_kernel: #endif /* chose register bank #0 */ lr r0, [_ARC_V2_STATUS32] and r0, r0, ~_ARC_V2_STATUS32_RB(7) kflag r0 _firq_create_irq_stack_frame: /* we're back on the outgoing thread's stack */ _create_irq_stack_frame /* * In a FIRQ, STATUS32 of the outgoing thread is in STATUS32_P0 and the * PC in ILINK: save them in status32/pc respectively. */ lr r0, [_ARC_V2_STATUS32_P0] st_s r0, [sp, ___isf_t_status32_OFFSET] st ilink, [sp, ___isf_t_pc_OFFSET] /* ilink into pc */ /* * load r0, r2 from irq stack */ _get_curr_cpu_irq_stack r1 ld r0, [r1, -4] ld r2, [r1, -8] #endif /* r2 is old thread */ _irq_store_old_thread_callee_regs st _CAUSE_FIRQ, [r2, _thread_offset_to_relinquish_cause] /* mov new thread (r0) to r2 */ mov r2, r0 _load_new_thread_callee_regs breq r3, _CAUSE_RIRQ, _firq_switch_from_rirq nop_s breq r3, _CAUSE_FIRQ, _firq_switch_from_firq nop_s /* fall through */ .balign 4 _firq_switch_from_coop: _set_misc_regs_irq_switch_from_coop /* pc into ilink */ pop_s r0 mov_s ilink, r0 pop_s r0 /* status32 into r0 */ sr r0, [_ARC_V2_STATUS32_P0] rtie .balign 4 _firq_switch_from_rirq: _firq_switch_from_firq: _set_misc_regs_irq_switch_from_irq _pop_irq_stack_frame ld ilink, [sp, -4] /* status32 into ilink */ sr ilink, [_ARC_V2_STATUS32_P0] ld ilink, [sp, -8] /* pc into ilink */ /* LP registers are already restored, just switch back to bank 0 */ rtie