Initial import

1 files changed, 156 insertions, 0 deletions

diff --git a/arch/sh/boards/mach-dreamcast/irq.c b/arch/sh/boards/mach-dreamcast/irq.c
new file mode 100644
index 000000000..2789647ab
--- /dev/null
+++ b/arch/sh/boards/mach-dreamcast/irq.c
@@ -0,0 +1,156 @@
+/*
+ * 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 <linux/irq.h>
+#include <linux/export.h>
+#include <linux/err.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 position 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(struct irq_data *data)
+{
+	unsigned int irq = data->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(struct irq_data *data)
+{
+	unsigned int irq = data->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(struct irq_data *data)
+{
+	unsigned int irq = data->irq;
+	__u32 esr = ESR_BASE + (LEVEL(irq) << 2);
+	disable_systemasic_irq(data);
+	outl((1 << EVENT_BIT(irq)), esr);
+}
+
+struct irq_chip systemasic_int = {
+	.name		= "System ASIC",
+	.irq_mask	= disable_systemasic_irq,
+	.irq_mask_ack	= mask_ack_systemasic_irq,
+	.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;
+}
+
+void systemasic_irq_init(void)
+{
+	int irq_base, i;
+
+	irq_base = irq_alloc_descs(HW_EVENT_IRQ_BASE, HW_EVENT_IRQ_BASE,
+				   HW_EVENT_IRQ_MAX - HW_EVENT_IRQ_BASE, -1);
+	if (IS_ERR_VALUE(irq_base)) {
+		pr_err("%s: failed hooking irqs\n", __func__);
+		return;
+	}
+
+	for (i = HW_EVENT_IRQ_BASE; i < HW_EVENT_IRQ_MAX; i++)
+		irq_set_chip_and_handler(i, &systemasic_int, handle_level_irq);
+}