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/*
* arch/sh/boards/dreamcast/irq.c
*
* Holly IRQ support for the Sega Dreamcast.
*
* Copyright (c) 2001, 2002 M. R. Brown <mrbrown@0xd6.org>
*
* This file is part of the LinuxDC project (www.linuxdc.org)
* Released under the terms of the GNU GPL v2.0
*/
#include <linux/irq.h>
#include <linux/io.h>
#include <asm/irq.h>
#include <mach/sysasic.h>
/*
* Dreamcast System ASIC Hardware Events -
*
* The Dreamcast's System ASIC (a.k.a. Holly) is responsible for receiving
* hardware events from system peripherals and triggering an SH7750 IRQ.
* Hardware events can trigger IRQs 13, 11, or 9 depending on which bits are
* set in the Event Mask Registers (EMRs). When a hardware event is
* triggered, its corresponding bit in the Event Status Registers (ESRs)
* is set, and that bit should be rewritten to the ESR to acknowledge that
* event.
*
* There are three 32-bit ESRs located at 0xa05f6900 - 0xa05f6908. Event
* types can be found in arch/sh/include/mach-dreamcast/mach/sysasic.h.
* There are three groups of EMRs that parallel the ESRs. Each EMR group
* corresponds to an IRQ, so 0xa05f6910 - 0xa05f6918 triggers IRQ 13,
* 0xa05f6920 - 0xa05f6928 triggers IRQ 11, and 0xa05f6930 - 0xa05f6938
* triggers IRQ 9.
*
* In the kernel, these events are mapped to virtual IRQs so that drivers can
* respond to them as they would a normal interrupt. In order to keep this
* mapping simple, the events are mapped as:
*
* 6900/6910 - Events 0-31, IRQ 13
* 6904/6924 - Events 32-63, IRQ 11
* 6908/6938 - Events 64-95, IRQ 9
*
*/
#define ESR_BASE 0x005f6900 /* Base event status register */
#define EMR_BASE 0x005f6910 /* Base event mask register */
/*
* Helps us determine the EMR group that this event belongs to: 0 = 0x6910,
* 1 = 0x6920, 2 = 0x6930; also determine the event offset.
*/
#define LEVEL(event) (((event) - HW_EVENT_IRQ_BASE) / 32)
/* Return the hardware event's bit positon within the EMR/ESR */
#define EVENT_BIT(event) (((event) - HW_EVENT_IRQ_BASE) & 31)
/*
* For each of these *_irq routines, the IRQ passed in is the virtual IRQ
* (logically mapped to the corresponding bit for the hardware event).
*/
/* Disable the hardware event by masking its bit in its EMR */
static inline void disable_systemasic_irq(unsigned int irq)
{
__u32 emr = EMR_BASE + (LEVEL(irq) << 4) + (LEVEL(irq) << 2);
__u32 mask;
mask = inl(emr);
mask &= ~(1 << EVENT_BIT(irq));
outl(mask, emr);
}
/* Enable the hardware event by setting its bit in its EMR */
static inline void enable_systemasic_irq(unsigned int irq)
{
__u32 emr = EMR_BASE + (LEVEL(irq) << 4) + (LEVEL(irq) << 2);
__u32 mask;
mask = inl(emr);
mask |= (1 << EVENT_BIT(irq));
outl(mask, emr);
}
/* Acknowledge a hardware event by writing its bit back to its ESR */
static void mask_ack_systemasic_irq(unsigned int irq)
{
__u32 esr = ESR_BASE + (LEVEL(irq) << 2);
disable_systemasic_irq(irq);
outl((1 << EVENT_BIT(irq)), esr);
}
struct irq_chip systemasic_int = {
.name = "System ASIC",
.mask = disable_systemasic_irq,
.mask_ack = mask_ack_systemasic_irq,
.unmask = enable_systemasic_irq,
};
/*
* Map the hardware event indicated by the processor IRQ to a virtual IRQ.
*/
int systemasic_irq_demux(int irq)
{
__u32 emr, esr, status, level;
__u32 j, bit;
switch (irq) {
case 13:
level = 0;
break;
case 11:
level = 1;
break;
case 9:
level = 2;
break;
default:
return irq;
}
emr = EMR_BASE + (level << 4) + (level << 2);
esr = ESR_BASE + (level << 2);
/* Mask the ESR to filter any spurious, unwanted interrupts */
status = inl(esr);
status &= inl(emr);
/* Now scan and find the first set bit as the event to map */
for (bit = 1, j = 0; j < 32; bit <<= 1, j++) {
if (status & bit) {
irq = HW_EVENT_IRQ_BASE + j + (level << 5);
return irq;
}
}
/* Not reached */
return irq;
}
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