1 files changed, 160 insertions, 0 deletions

diff --git a/arch/sh/boards/dreamcast/irq.c b/arch/sh/boards/dreamcast/irq.c
new file mode 100644
index 000000000000..b10a6b11c034
--- /dev/null
+++ b/arch/sh/boards/dreamcast/irq.c
@@ -0,0 +1,160 @@
+/*
+ * 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 <asm/io.h>
+#include <asm/irq.h>
+#include <asm/dreamcast/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, it's 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 0xa05f8900 - 0xa05f6908.  Event
+   types can be found in include/asm-sh/dc_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)
+{
+        unsigned long flags;
+        __u32 emr = EMR_BASE + (LEVEL(irq) << 4) + (LEVEL(irq) << 2);
+        __u32 mask;
+
+        local_irq_save(flags);
+        mask = inl(emr);
+        mask &= ~(1 << EVENT_BIT(irq));
+        outl(mask, emr);
+        local_irq_restore(flags);
+}
+
+/* Enable the hardware event by setting its bit in its EMR */
+static inline void enable_systemasic_irq(unsigned int irq)
+{
+        unsigned long flags;
+        __u32 emr = EMR_BASE + (LEVEL(irq) << 4) + (LEVEL(irq) << 2);
+        __u32 mask;
+
+        local_irq_save(flags);
+        mask = inl(emr);
+        mask |= (1 << EVENT_BIT(irq));
+        outl(mask, emr);
+        local_irq_restore(flags);
+}
+
+/* Acknowledge a hardware event by writing its bit back to its ESR */
+static void ack_systemasic_irq(unsigned int irq)
+{
+        __u32 esr = ESR_BASE + (LEVEL(irq) << 2);
+        disable_systemasic_irq(irq);
+        outl((1 << EVENT_BIT(irq)), esr);
+}
+
+/* After a IRQ has been ack'd and responded to, it needs to be renabled */
+static void end_systemasic_irq(unsigned int irq)
+{
+        if (!(irq_desc[irq].status & (IRQ_DISABLED|IRQ_INPROGRESS)))
+                enable_systemasic_irq(irq);
+}
+
+static unsigned int startup_systemasic_irq(unsigned int irq)
+{
+        enable_systemasic_irq(irq);
+
+        return 0;
+}
+
+static void shutdown_systemasic_irq(unsigned int irq)
+{
+        disable_systemasic_irq(irq);
+}
+
+struct hw_interrupt_type systemasic_int = {
+        .typename       = "System ASIC",
+        .startup        = startup_systemasic_irq,
+        .shutdown       = shutdown_systemasic_irq,
+        .enable         = enable_systemasic_irq,
+        .disable        = disable_systemasic_irq,
+        .ack            = ack_systemasic_irq,
+        .end            = end_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 interrtupts */
+        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;
+}