/* * linux/arch/arm/kernel/fiq.c * * Copyright (C) 1998 Russell King * Copyright (C) 1998, 1999 Phil Blundell * * FIQ support written by Philip Blundell , 1998. * * FIQ support re-written by Russell King to be more generic * * FIQ handler in C supoprt written by Andy Green * * We now properly support a method by which the FIQ handlers can * be stacked onto the vector. We still do not support sharing * the FIQ vector itself. * * Operation is as follows: * 1. Owner A claims FIQ: * - default_fiq relinquishes control. * 2. Owner A: * - inserts code. * - sets any registers, * - enables FIQ. * 3. Owner B claims FIQ: * - if owner A has a relinquish function. * - disable FIQs. * - saves any registers. * - returns zero. * 4. Owner B: * - inserts code. * - sets any registers, * - enables FIQ. * 5. Owner B releases FIQ: * - Owner A is asked to reacquire FIQ: * - inserts code. * - restores saved registers. * - enables FIQ. * 6. Goto 3 */ #include #include #include #include #include #include #include #include #include static unsigned long no_fiq_insn; /* Default reacquire function * - we always relinquish FIQ control * - we always reacquire FIQ control */ static int fiq_def_op(void *ref, int relinquish) { if (!relinquish) set_fiq_handler(&no_fiq_insn, sizeof(no_fiq_insn)); return 0; } static struct fiq_handler default_owner = { .name = "default", .fiq_op = fiq_def_op, }; static struct fiq_handler *current_fiq = &default_owner; int show_fiq_list(struct seq_file *p, void *v) { if (current_fiq != &default_owner) seq_printf(p, "FIQ: %s\n", current_fiq->name); return 0; } void set_fiq_handler(void *start, unsigned int length) { memcpy((void *)0xffff001c, start, length); flush_icache_range(0xffff001c, 0xffff001c + length); if (!vectors_high()) flush_icache_range(0x1c, 0x1c + length); } /* * Taking an interrupt in FIQ mode is death, so both these functions * disable irqs for the duration. Note - these functions are almost * entirely coded in assembly. */ void __attribute__((naked)) set_fiq_regs(struct pt_regs *regs) { register unsigned long tmp; asm volatile ( "mov ip, sp\n\ stmfd sp!, {fp, ip, lr, pc}\n\ sub fp, ip, #4\n\ mrs %0, cpsr\n\ msr cpsr_c, %2 @ select FIQ mode\n\ mov r0, r0\n\ ldmia %1, {r8 - r14}\n\ msr cpsr_c, %0 @ return to SVC mode\n\ mov r0, r0\n\ ldmfd sp, {fp, sp, pc}" : "=&r" (tmp) : "r" (®s->ARM_r8), "I" (PSR_I_BIT | PSR_F_BIT | FIQ_MODE)); } void __attribute__((naked)) get_fiq_regs(struct pt_regs *regs) { register unsigned long tmp; asm volatile ( "mov ip, sp\n\ stmfd sp!, {fp, ip, lr, pc}\n\ sub fp, ip, #4\n\ mrs %0, cpsr\n\ msr cpsr_c, %2 @ select FIQ mode\n\ mov r0, r0\n\ stmia %1, {r8 - r14}\n\ msr cpsr_c, %0 @ return to SVC mode\n\ mov r0, r0\n\ ldmfd sp, {fp, sp, pc}" : "=&r" (tmp) : "r" (®s->ARM_r8), "I" (PSR_I_BIT | PSR_F_BIT | FIQ_MODE)); } /* -------- FIQ handler in C --------- * * Major Caveats for using this * --------------------------- * * * * 1) it CANNOT touch any vmalloc()'d memory, only memory * that was kmalloc()'d. Static allocations in the monolithic kernel * are kmalloc()'d so they are okay. You can touch memory-mapped IO, but * the pointer for it has to have been stored in kmalloc'd memory. The * reason for this is simple: every now and then Linux turns off interrupts * and reorders the paging tables. If a FIQ happens during this time, the * virtual memory space can be partly or entirely disordered or missing. * * 2) Because vmalloc() is used when a module is inserted, THIS FIQ * ISR HAS TO BE IN THE MONOLITHIC KERNEL, not a module. But the way * it is set up, you can all to enable and disable it from your module * and intercommunicate with it through struct fiq_ipc * fiq_ipc which you can define in * asm/archfiq_ipc_type.h. The reason is the same as above, a * FIQ could happen while even the ISR is not present in virtual memory * space due to pagetables being changed at the time. * * 3) You can't call any Linux API code except simple macros * - understand that FIQ can come in at any time, no matter what * state of undress the kernel may privately be in, thinking it * locked the door by turning off interrupts... FIQ is an * unstoppable monster force (which is its value) * - they are not vmalloc()'d memory safe * - they might do crazy stuff like sleep: FIQ pisses fire and * is not interested in 'sleep' that the weak seem to need * - calling APIs from FIQ can re-enter un-renterable things * - summary: you cannot interoperate with linux APIs directly in the FIQ ISR * * If you follow these rules, it is fantastic, an extremely powerful, solid, * genuine hard realtime feature. */ static void (*current_fiq_c_isr)(void); #define FIQ_C_ISR_STACK_SIZE 256 static void __attribute__((naked)) __jump_to_isr(void) { asm __volatile__ ("mov pc, r8"); } static void __attribute__((naked)) __actual_isr(void) { asm __volatile__ ( "stmdb sp!, {r0-r12, lr};" "mov fp, sp;" ); current_fiq_c_isr(); asm __volatile__ ( "ldmia sp!, {r0-r12, lr};" "subs pc, lr, #4;" ); } void set_fiq_c_handler(void (*isr)(void)) { struct pt_regs regs; memset(®s, 0, sizeof(regs)); regs.ARM_r8 = (unsigned long) __actual_isr; regs.ARM_sp = 0xffff001c + FIQ_C_ISR_STACK_SIZE; set_fiq_handler(__jump_to_isr, 4); current_fiq_c_isr = isr; set_fiq_regs(®s); } /* -------- FIQ handler in C ---------*/ int claim_fiq(struct fiq_handler *f) { int ret = 0; if (current_fiq) { ret = -EBUSY; if (current_fiq->fiq_op != NULL) ret = current_fiq->fiq_op(current_fiq->dev_id, 1); } if (!ret) { f->next = current_fiq; current_fiq = f; } return ret; } void release_fiq(struct fiq_handler *f) { if (current_fiq != f) { printk(KERN_ERR "%s FIQ trying to release %s FIQ\n", f->name, current_fiq->name); dump_stack(); return; } do current_fiq = current_fiq->next; while (current_fiq->fiq_op(current_fiq->dev_id, 0)); } void enable_fiq(int fiq) { enable_irq(fiq + FIQ_START); } void disable_fiq(int fiq) { disable_irq(fiq + FIQ_START); } EXPORT_SYMBOL(set_fiq_handler); EXPORT_SYMBOL(set_fiq_regs); EXPORT_SYMBOL(get_fiq_regs); EXPORT_SYMBOL(claim_fiq); EXPORT_SYMBOL(release_fiq); EXPORT_SYMBOL(enable_fiq); EXPORT_SYMBOL(disable_fiq); void __init init_FIQ(void) { no_fiq_insn = *(unsigned long *)0xffff001c; }