arch/sh/boards/mach-dreamcast/irq.c

   1 /*
   2  * arch/sh/boards/dreamcast/irq.c
   3  *
   4  * Holly IRQ support for the Sega Dreamcast.
   5  *
   6  * Copyright (c) 2001, 2002 M. R. Brown <mrbrown@0xd6.org>
   7  *
   8  * This file is part of the LinuxDC project (www.linuxdc.org)
   9  * Released under the terms of the GNU GPL v2.0
  10  */
  11
  12 #include <linux/irq.h>
  13 #include <linux/io.h>
  14 #include <asm/irq.h>
  15 #include <mach/sysasic.h>
  16
  17 /*
  18  * Dreamcast System ASIC Hardware Events -
  19  *
  20  * The Dreamcast's System ASIC (a.k.a. Holly) is responsible for receiving
  21  * hardware events from system peripherals and triggering an SH7750 IRQ.
  22  * Hardware events can trigger IRQs 13, 11, or 9 depending on which bits are
  23  * set in the Event Mask Registers (EMRs).  When a hardware event is
  24  * triggered, its corresponding bit in the Event Status Registers (ESRs)
  25  * is set, and that bit should be rewritten to the ESR to acknowledge that
  26  * event.
  27  *
  28  * There are three 32-bit ESRs located at 0xa05f6900 - 0xa05f6908.  Event
  29  * types can be found in arch/sh/include/mach-dreamcast/mach/sysasic.h.
  30  * There are three groups of EMRs that parallel the ESRs.  Each EMR group
  31  * corresponds to an IRQ, so 0xa05f6910 - 0xa05f6918 triggers IRQ 13,
  32  * 0xa05f6920 - 0xa05f6928 triggers IRQ 11, and 0xa05f6930 - 0xa05f6938
  33  * triggers IRQ 9.
  34  *
  35  * In the kernel, these events are mapped to virtual IRQs so that drivers can
  36  * respond to them as they would a normal interrupt.  In order to keep this
  37  * mapping simple, the events are mapped as:
  38  *
  39  * 6900/6910 - Events  0-31, IRQ 13
  40  * 6904/6924 - Events 32-63, IRQ 11
  41  * 6908/6938 - Events 64-95, IRQ  9
  42  *
  43  */
  44
  45 #define ESR_BASE 0x005f6900    /* Base event status register */
  46 #define EMR_BASE 0x005f6910    /* Base event mask register */
  47
  48 /*
  49  * Helps us determine the EMR group that this event belongs to: 0 = 0x6910,
  50  * 1 = 0x6920, 2 = 0x6930; also determine the event offset.
  51  */
  52 #define LEVEL(event) (((event) - HW_EVENT_IRQ_BASE) / 32)
  53
  54 /* Return the hardware event's bit positon within the EMR/ESR */
  55 #define EVENT_BIT(event) (((event) - HW_EVENT_IRQ_BASE) & 31)
  56
  57 /*
  58  * For each of these *_irq routines, the IRQ passed in is the virtual IRQ
  59  * (logically mapped to the corresponding bit for the hardware event).
  60  */
  61
  62 /* Disable the hardware event by masking its bit in its EMR */
  63 static inline void disable_systemasic_irq(unsigned int irq)
  64 {
  65         __u32 emr = EMR_BASE + (LEVEL(irq) << 4) + (LEVEL(irq) << 2);
  66         __u32 mask;
  67
  68         mask = inl(emr);
  69         mask &= ~(1 << EVENT_BIT(irq));
  70         outl(mask, emr);
  71 }
  72
  73 /* Enable the hardware event by setting its bit in its EMR */
  74 static inline void enable_systemasic_irq(unsigned int irq)
  75 {
  76         __u32 emr = EMR_BASE + (LEVEL(irq) << 4) + (LEVEL(irq) << 2);
  77         __u32 mask;
  78
  79         mask = inl(emr);
  80         mask |= (1 << EVENT_BIT(irq));
  81         outl(mask, emr);
  82 }
  83
  84 /* Acknowledge a hardware event by writing its bit back to its ESR */
  85 static void mask_ack_systemasic_irq(unsigned int irq)
  86 {
  87         __u32 esr = ESR_BASE + (LEVEL(irq) << 2);
  88         disable_systemasic_irq(irq);
  89         outl((1 << EVENT_BIT(irq)), esr);
  90 }
  91
  92 struct irq_chip systemasic_int = {
  93         .name           = "System ASIC",
  94         .mask           = disable_systemasic_irq,
  95         .mask_ack       = mask_ack_systemasic_irq,
  96         .unmask         = enable_systemasic_irq,
  97 };
  98
  99 /*
 100  * Map the hardware event indicated by the processor IRQ to a virtual IRQ.
 101  */
 102 int systemasic_irq_demux(int irq)
 103 {
 104         __u32 emr, esr, status, level;
 105         __u32 j, bit;
 106
 107         switch (irq) {
 108         case 13:
 109                 level = 0;
 110                 break;
 111         case 11:
 112                 level = 1;
 113                 break;
 114         case  9:
 115                 level = 2;
 116                 break;
 117         default:
 118                 return irq;
 119         }
 120         emr = EMR_BASE + (level << 4) + (level << 2);
 121         esr = ESR_BASE + (level << 2);
 122
 123         /* Mask the ESR to filter any spurious, unwanted interrupts */
 124         status = inl(esr);
 125         status &= inl(emr);
 126
 127         /* Now scan and find the first set bit as the event to map */
 128         for (bit = 1, j = 0; j < 32; bit <<= 1, j++) {
 129                 if (status & bit) {
 130                         irq = HW_EVENT_IRQ_BASE + j + (level << 5);
 131                         return irq;
 132                 }
 133         }
 134
 135         /* Not reached */
 136         return irq;
 137 }