Interrupts

IRQs and ISRs for the SH4's CPU. More...

Modules
	Exception Codes
	IRQ exception code values.
	Exception type offsets
	Offsets within exception types.

Files
file	irq.h
	Interrupt and exception handling.

Data Structures
struct	irq_context_t
	Architecture-specific structure for holding the processor state. More...

Macros
#define	REG_BYTE_CNT   256 /* Currently really 228 */
	The number of bytes required to save thread context.
#define	CONTEXT_PC(c)   ((c).pc)
	Fetch the program counter from an irq_context_t.
#define	CONTEXT_FP(c)   ((c).r[14])
	Fetch the frame pointer from an irq_context_t.
#define	CONTEXT_SP(c)   ((c).r[15])
	Fetch the stack pointer from an irq_context_t.
#define	CONTEXT_RET(c)   ((c).r[0])
	Fetch the return value from an irq_context_t.
#define	TIMER_IRQ   EXC_TMU0_TUNI0
	The value of the timer IRQ.

Typedefs
typedef uint32_t	irq_t
	The type of an interrupt identifier.
typedef void(*	irq_handler) (irq_t source, irq_context_t *context, void *data)
	The type of an IRQ handler.

Functions
int	irq_inside_int (void)
	Are we inside an interrupt handler?
void	irq_force_return (void)
	Pretend like we just came in from an interrupt and force a context switch back to the "current" context.
int	irq_set_handler (irq_t source, irq_handler hnd, void *data)
	Set or remove an IRQ handler.
irq_handler	irq_get_handler (irq_t source)
	Get the address of the current handler for the IRQ type.
int	trapa_set_handler (irq_t code, irq_handler hnd, void *data)
	Set or remove a handler for a trapa code.
int	irq_set_global_handler (irq_handler hnd, void *data)
	Set a global exception handler.
irq_handler	irq_get_global_handler (void)
	Get the global exception handler.
void	irq_set_context (irq_context_t *regbank)
	Switch out contexts (for interrupt return).
irq_context_t *	irq_get_context (void)
	Get the current IRQ context.
void	irq_create_context (irq_context_t *context, uint32_t stack_pointer, uint32_t routine, uint32_t *args, int usermode)
	Fill a newly allocated context block for usage with supervisor or user mode.
int	irq_disable (void)
	Disable interrupts.
void	irq_enable (void)
	Enable all interrupts.
void	irq_restore (int v)
	Restore IRQ state.
int	irq_init (void)
	Initialize interrupts.
void	irq_shutdown (void)
	Shutdown interrupts, restoring the state to how it was before irq_init() was called.

Detailed Description

IRQs and ISRs for the SH4's CPU.

Macro Definition Documentation

CONTEXT_FP

#define CONTEXT_FP

(

c

)

((c).r[14])

Fetch the frame pointer from an irq_context_t.

Parameters

c	The context to read from.

Returns

The frame pointer value.

CONTEXT_PC

#define CONTEXT_PC

(

c

)

((c).pc)

Fetch the program counter from an irq_context_t.

Parameters

c	The context to read from.

Returns

The program counter value.

CONTEXT_RET

#define CONTEXT_RET

(

c

)

((c).r[0])

Fetch the return value from an irq_context_t.

Parameters

c	The context to read from.

Returns

The return value.

CONTEXT_SP

#define CONTEXT_SP

(

c

)

((c).r[15])

Fetch the stack pointer from an irq_context_t.

Parameters

c	The context to read from.

Returns

The stack pointer value.

REG_BYTE_CNT

#define REG_BYTE_CNT   256 /* Currently really 228 */

The number of bytes required to save thread context.

This should include all general CPU registers, FP registers, and status regs (even if not all of these are actually used).

On the Dreamcast, we need 228 bytes for all of that, but we round it up to a nicer number for sanity.

TIMER_IRQ

#define TIMER_IRQ   EXC_TMU0_TUNI0

The value of the timer IRQ.

Typedef Documentation

irq_handler

typedef void(* irq_handler) (irq_t source, irq_context_t *context, void *data)

The type of an IRQ handler.

Parameters

source	The IRQ that caused the handler to be called.
context	The CPU's context.

irq_t

typedef uint32_t irq_t

The type of an interrupt identifier.

Function Documentation

irq_create_context()

void irq_create_context	(	irq_context_t *	context,
		uint32_t	stack_pointer,
		uint32_t	routine,
		uint32_t *	args,
		int	usermode
	)

Fill a newly allocated context block for usage with supervisor or user mode.

The given parameters will be passed to the called routine (up to the architecture maximum). For the Dreamcast, this maximum is 4.

Parameters

context	The IRQ context to fill in.
stack_pointer	The value to set in the stack pointer.
routine	The address of the program counter for the context.
args	Any arguments to set in the registers. This cannot be NULL, and must have enough values to fill in up to the architecture maximum.
usermode	1 to run the routine in user mode, 0 for supervisor.

irq_disable()

int irq_disable

(

void

)

Disable interrupts.

This function will disable interrupts, but will leave exceptions enabled.

Returns

The state of IRQs before calling the function. This can be used to restore this state later on with irq_restore().

Referenced by g2_lock().

irq_enable()

void irq_enable

(

void

)

Enable all interrupts.

This function will enable ALL interrupts, including external ones.

irq_force_return()

void irq_force_return

(

void

)

Pretend like we just came in from an interrupt and force a context switch back to the "current" context.

Warning

Make sure you've called irq_set_context() before doing this!

irq_get_context()

irq_context_t * irq_get_context

(

void

)

Get the current IRQ context.

This will fetch the processor context prior to the exception handling during an IRQ service routine.

Returns

The current IRQ context.

irq_get_global_handler()

irq_handler irq_get_global_handler

(

void

)

Get the global exception handler.

Returns

The global exception handler set with irq_set_global_handler(), or NULL if none is set.

irq_get_handler()

irq_handler irq_get_handler

(

irq_t

source

)

Get the address of the current handler for the IRQ type.

Parameters

source

The IRQ type to look up.

Returns

A pointer to the procedure to handle the exception.

irq_init()

int irq_init

(

void

)

Initialize interrupts.

Return values

0	On success (no error conditions defined).

irq_inside_int()

int irq_inside_int

(

void

)

Are we inside an interrupt handler?

Return values

1	If interrupt handling is in progress.
0	If normal processing is in progress.

irq_restore()

void irq_restore

(

int

v

)

Restore IRQ state.

This function will restore the interrupt state to the value specified. This should correspond to a value returned by irq_disable().

Parameters

v	The IRQ state to restore. This should be a value returned by irq_disable().

Referenced by g2_unlock().

irq_set_context()

void irq_set_context

(

irq_context_t *

regbank

)

Switch out contexts (for interrupt return).

This function will set the processor state that will be restored when the exception returns.

Parameters

regbank

The values of all registers to be restored.

irq_set_global_handler()

int irq_set_global_handler	(	irq_handler	hnd,
		void *	data
	)

Set a global exception handler.

This function sets a global catch-all handler for all exception types.

Note

The specific handler will still be called for the exception if one is set. If not, setting one of these will stop the unhandled exception error.

Parameters

hnd	A pointer to the procedure to handle the exception.
data	A pointer that will be passed along to the callback.

Return values

0	On success (no error conditions defined).

irq_set_handler()

int irq_set_handler	(	irq_t	source,
		irq_handler	hnd,
		void *	data
	)

Set or remove an IRQ handler.

Passing a NULL value for hnd will remove the current handler, if any.

Parameters

source	The IRQ type to set the handler for (see Exception Codes).
hnd	A pointer to a procedure to handle the exception.
data	A pointer that will be passed along to the callback.

Return values

0	On success.
-1	If the source is invalid.

irq_shutdown()

void irq_shutdown

(

void

)

Shutdown interrupts, restoring the state to how it was before irq_init() was called.

trapa_set_handler()

int trapa_set_handler	(	irq_t	code,
		irq_handler	hnd,
		void *	data
	)

Set or remove a handler for a trapa code.

Parameters

code	The value passed to the trapa opcode.
hnd	A pointer to the procedure to handle the trap.
data	A pointer that will be passed along to the callback.

Return values

0	On success.
-1	If the code is invalid (greater than 0xFF).