Linux中斷體系結構
1.中斷處理體系結構
Linux內核將所有中斷統一編號,使用一個irq_desc結構數組來描述這些中斷。
數組聲明在/linux/kernel/irq/handle.c中,其中#define NR_IRQS 128,定義在/linux/include/asm/irq.h中
1 /* 2 * Linux has a controller-independent interrupt architecture. 3 * Every controller has a ‘controller-template‘, that is used 4 * by the main code to do the right thing. Each driver-visibleirq_desc結構的數據類型在/linuxinclude/linux/irq.h中定義,5 * interrupt source is transparently wired to the appropriate 6 * controller. Thus drivers need not be aware of the 7 * interrupt-controller. 8 * 9 * The code is designed to be easily extended with new/different 10 * interrupt controllers, without having to do assembly magic or 11 * having to touch the generic code.12 * 13 * Controller mappings for all interrupt sources: 14 */ 15 struct irq_desc irq_desc[NR_IRQS] __cacheline_aligned_in_smp = { 16 [0 ... NR_IRQS-1] = { 17 .status = IRQ_DISABLED, 18 .chip = &no_irq_chip, 19 .handle_irq = handle_bad_irq, 20 .depth = 1, 21 .lock= __SPIN_LOCK_UNLOCKED(irq_desc->lock), 22 #ifdef CONFIG_SMP 23 .affinity = CPU_MASK_ALL 24 #endif 25 } 26 };
1 struct irq_desc { 2 irq_flow_handler_t handle_irq; 3 struct irq_chip *chip; 4 struct msi_desc *msi_desc; 5 void *handler_data; 6 void *chip_data; 7 struct irqaction *action; /* IRQ action list */ 8 unsigned int status; /* IRQ status */ 9 10 unsigned int depth; /* nested irq disables */ 11 unsigned int wake_depth; /* nested wake enables */ 12 unsigned int irq_count; /* For detecting broken IRQs */ 13 unsigned int irqs_unhandled; 14 spinlock_t lock; 15 #ifdef CONFIG_SMP 16 cpumask_t affinity; 17 unsigned int cpu; 18 #endif 19 #if defined(CONFIG_GENERIC_PENDING_IRQ) || defined(CONFIG_IRQBALANCE) 20 cpumask_t pending_mask; 21 #endif 22 #ifdef CONFIG_PROC_FS 23 struct proc_dir_entry *dir; 24 #endif 25 const char *name; 26 } ____cacheline_internodealigned_in_smp;
handle_irq是這個或這組中斷的處理函數入口。發生中斷時,總入口函數asm_do_IRQ將根據中斷號調用相應irq_desc數組項中handle_irq.
typedef void fastcall (*irq_flow_handler_t)(unsigned int irq, struct irq_desc *desc);
handle_irq使用chip結構中的函數清除、屏蔽或者重新使能中斷,還要調用用戶在action鏈表中註冊的中斷處理函數。irq_chip結構類型也是在include/linux/irq.h中定義,其中的成員大多用於操作底層硬件,比如設置寄存器以屏蔽中斷,使能中斷,清除中斷等。註意這裏的成員name會出現在/proc/interrupts中。
struct irq_chip { const char *name; unsigned int (*startup)(unsigned int irq); void (*shutdown)(unsigned int irq); void (*enable)(unsigned int irq); void (*disable)(unsigned int irq); void (*ack)(unsigned int irq); void (*mask)(unsigned int irq); void (*mask_ack)(unsigned int irq); void (*unmask)(unsigned int irq); void (*eoi)(unsigned int irq); void (*end)(unsigned int irq); void (*set_affinity)(unsigned int irq, cpumask_t dest); int (*retrigger)(unsigned int irq); int (*set_type)(unsigned int irq, unsigned int flow_type); int (*set_wake)(unsigned int irq, unsigned int on); /* Currently used only by UML, might disappear one day.*/ #ifdef CONFIG_IRQ_RELEASE_METHOD void (*release)(unsigned int irq, void *dev_id); #endif /* * For compatibility, ->typename is copied into ->name. * Will disappear. */ const char *typename; };
irq_desc結構中的irqaction結構類型在include/linux/iterrupt.h中定義。用戶註冊的每個中斷處理函數用一個irqaction結構來表示,一個中斷比如共享中斷可以有多個處理函數,它們的irqaction結構鏈接成一個鏈表,以action為表頭。irqation結構在linux/include/linux/interrupt.h中定義如下:
typedef irqreturn_t (*irq_handler_t)(int, void *); struct irqaction { irq_handler_t handler; unsigned long flags; cpumask_t mask; const char *name; void *dev_id; struct irqaction *next; int irq; struct proc_dir_entry *dir; };
irq_desc結構數組、它的成員“struct irq_chip *chip” "struct irqaction *action",這3種數據結構構成了中斷處理體系的框架。下圖中描述了Linxu中斷處理體系結構的關系圖:
中斷處理流程如下(1)發生中斷時,CPU執行異常向量vector_irq的代碼
(2)在vector_irq裏面,最終會調用中斷處理的總入口函數asm_do_IRQ
(3)asm_do_IRQ根據中斷號調用irq_desc數組項中的handle_irq。
(4)handle_irq會使用chip成員中的函數來設置硬件,比如清除中斷、禁止中斷、重新使能中斷等
(5)handle_irq逐個調用用戶在aciton鏈表中註冊的處理函數
中斷體系結構的初始化就是構造這些數據結構,比如irq_desc數組項中的handle_irq、chip等成員;用戶註冊中斷時就是構造action鏈表;用戶卸載中斷時就是從action鏈表中去除不需要的項。 2.中斷處理體系結構的初始化 init_IRQ函數被用來初始化中斷處理體系結構,代碼在arch/arm/kernel/irq.c中
void __init init_IRQ(void) { int irq; for (irq = 0; irq < NR_IRQS; irq++) irq_desc[irq].status |= IRQ_NOREQUEST | IRQ_NOPROBE; #ifdef CONFIG_SMP bad_irq_desc.affinity = CPU_MASK_ALL; bad_irq_desc.cpu = smp_processor_id(); #endif init_arch_irq(); }
下面簡單分析下init_arch_irq();的獲取過程及調用順序
1 /* 2 init_arch_irq()的由來 3 定義一個空函數指針void (*init_arch_irq)(void) __initdata = NULL; 4 */ 5 asmlinkage void __init start_kernel(void) 6 -->setup_arch(&command_line); 7 -->init_arch_irq = mdesc->init_irq; 8 -->init_IRQ(); 9 -->init_arch_irq()//即mdesc->init_irq=s3c24xx_init_irq
上述machine_desc結構在/linux/arch/arm/mach-s3c2410/mach-bast.c如下宏中獲得,後面會分析machine_desc結構。
MACHINE_START(BAST, "Simtec-BAST") //Maintainer: Ben Dooks <[email protected]> .phys_io = S3C2410_PA_UART, .io_pg_offst = (((u32)S3C24XX_VA_UART) >> 18) & 0xfffc, .boot_params = S3C2410_SDRAM_PA + 0x100, .map_io = bast_map_io, .init_irq = s3c24xx_init_irq, .init_machine = bast_init, .timer = &s3c24xx_timer, MACHINE_END
對於S3C2440開發板,這個函數就是s3c24xx_init_irq,移植machine_desc結構中的init_irq成員就指向這個函數s3c24xx_init_irq函數在arch/arm/plat-s3c24xx/irq.c中定義,它為所有中斷設置了芯片相關的數據結構(irq_desc[irq].chip),設置了處理函數入口(irq_desc[irq].handle_irq)。
Linux中斷體系結構