[Qemu-devel] [RFC PATCH] ati-vga: Implement dummy VBlank IRQ

[BALATON Zoltan <balaton@eik.bme.hu>]

The MacOS driver exits if the card does not have an interrupt. If we
set PCI_INTERRUPT_PIN to 1 then it enables VBlank interrupts and it
boots but the mouse poniter can not be moved. This patch implements a
dummy VBlank interrupt by a timer triggered at 60 Hz to test if it
helps. Unfortunately it doesn't: MacOS with this patch hangs during
boot just polling interrupts and acknowledging them so maybe it needs
something else or there may be some other problem with this
implementation.

This is posted for comments and to let others experiment with it but
probably should not be committed upstream yet.

Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
---
 hw/display/ati.c      | 41 +++++++++++++++++++++++++++++++++++++++++
 hw/display/ati_dbg.c  |  1 +
 hw/display/ati_int.h  |  4 ++++
 hw/display/ati_regs.h |  1 +
 4 files changed, 47 insertions(+)

diff --git a/hw/display/ati.c b/hw/display/ati.c
index a365e2455d..e06cbf3e91 100644
--- a/hw/display/ati.c
+++ b/hw/display/ati.c
@@ -243,6 +243,21 @@ static uint64_t ati_i2c(bitbang_i2c_interface *i2c, uint64_t data, int base)
     return data;
 }
 
+static void ati_vga_update_irq(ATIVGAState *s)
+{
+    pci_set_irq(&s->dev, s->regs.gen_int_status & 1);
+}
+
+static void ati_vga_vblank_irq(void *opaque)
+{
+    ATIVGAState *s = opaque;
+
+    timer_mod(&s->vblank_timer, qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) +
+              NANOSECONDS_PER_SECOND / 60);
+    s->regs.gen_int_status |= 1;
+    ati_vga_update_irq(s);
+}
+
 static inline uint64_t ati_reg_read_offs(uint32_t reg, int offs,
                                          unsigned int size)
 {
@@ -283,6 +298,12 @@ static uint64_t ati_mm_read(void *opaque, hwaddr addr, unsigned int size)
                                 addr - (BIOS_0_SCRATCH + i * 4), size);
         break;
     }
+    case GEN_INT_CNTL:
+        val = s->regs.gen_int_cntl;
+        break;
+    case GEN_INT_STATUS:
+        val = s->regs.gen_int_status;
+        break;
     case CRTC_GEN_CNTL ... CRTC_GEN_CNTL + 3:
         val = ati_reg_read_offs(s->regs.crtc_gen_cntl,
                                 addr - CRTC_GEN_CNTL, size);
@@ -512,6 +533,19 @@ static void ati_mm_write(void *opaque, hwaddr addr,
                            addr - (BIOS_0_SCRATCH + i * 4), data, size);
         break;
     }
+    case GEN_INT_CNTL:
+        s->regs.gen_int_cntl = data;
+        if (data & 1) {
+            ati_vga_vblank_irq(s);
+        } else {
+            timer_del(&s->vblank_timer);
+        }
+        break;
+    case GEN_INT_STATUS:
+        data &= (s->dev_id == PCI_DEVICE_ID_ATI_RAGE128_PF ?
+                 0x000f040fUL : 0xfc080effUL);
+        s->regs.gen_int_status &= ~data;
+        break;
     case CRTC_GEN_CNTL ... CRTC_GEN_CNTL + 3:
     {
         uint32_t val = s->regs.crtc_gen_cntl;
@@ -902,12 +936,18 @@ static void ati_vga_realize(PCIDevice *dev, Error **errp)
     pci_register_bar(dev, 0, PCI_BASE_ADDRESS_MEM_PREFETCH, &vga->vram);
     pci_register_bar(dev, 1, PCI_BASE_ADDRESS_SPACE_IO, &s->io);
     pci_register_bar(dev, 2, PCI_BASE_ADDRESS_SPACE_MEMORY, &s->mm);
+
+    /* most interrupts are not yet emulated but MacOS needs at least VBlank */
+    dev->config[PCI_INTERRUPT_PIN] = 1;
+    timer_init_ns(&s->vblank_timer, QEMU_CLOCK_VIRTUAL, ati_vga_vblank_irq, s);
 }
 
 static void ati_vga_reset(DeviceState *dev)
 {
     ATIVGAState *s = ATI_VGA(dev);
 
+    timer_del(&s->vblank_timer);
+
     /* reset vga */
     vga_common_reset(&s->vga);
     s->mode = VGA_MODE;
@@ -917,6 +957,7 @@ static void ati_vga_exit(PCIDevice *dev)
 {
     ATIVGAState *s = ATI_VGA(dev);
 
+    timer_del(&s->vblank_timer);
     graphic_console_close(s->vga.con);
 }
 
diff --git a/hw/display/ati_dbg.c b/hw/display/ati_dbg.c
index 7e59c41ac2..0ebbd36f14 100644
--- a/hw/display/ati_dbg.c
+++ b/hw/display/ati_dbg.c
@@ -16,6 +16,7 @@ static struct ati_regdesc ati_reg_names[] = {
     {"BUS_CNTL", 0x0030},
     {"BUS_CNTL1", 0x0034},
     {"GEN_INT_CNTL", 0x0040},
+    {"GEN_INT_STATUS", 0x0044},
     {"CRTC_GEN_CNTL", 0x0050},
     {"CRTC_EXT_CNTL", 0x0054},
     {"DAC_CNTL", 0x0058},
diff --git a/hw/display/ati_int.h b/hw/display/ati_int.h
index 5b4d3be1e6..2a16708e4f 100644
--- a/hw/display/ati_int.h
+++ b/hw/display/ati_int.h
@@ -9,6 +9,7 @@
 #ifndef ATI_INT_H
 #define ATI_INT_H
 
+#include "qemu/timer.h"
 #include "hw/pci/pci.h"
 #include "hw/i2c/bitbang_i2c.h"
 #include "vga_int.h"
@@ -33,6 +34,8 @@
 typedef struct ATIVGARegs {
     uint32_t mm_index;
     uint32_t bios_scratch[8];
+    uint32_t gen_int_cntl;
+    uint32_t gen_int_status;
     uint32_t crtc_gen_cntl;
     uint32_t crtc_ext_cntl;
     uint32_t dac_cntl;
@@ -89,6 +92,7 @@ typedef struct ATIVGAState {
     uint16_t cursor_size;
     uint32_t cursor_offset;
     QEMUCursor *cursor;
+    QEMUTimer vblank_timer;
     bitbang_i2c_interface bbi2c;
     MemoryRegion io;
     MemoryRegion mm;
diff --git a/hw/display/ati_regs.h b/hw/display/ati_regs.h
index 02046e97c2..2b6f949bd4 100644
--- a/hw/display/ati_regs.h
+++ b/hw/display/ati_regs.h
@@ -34,6 +34,7 @@
 #define BUS_CNTL                                0x0030
 #define BUS_CNTL1                               0x0034
 #define GEN_INT_CNTL                            0x0040
+#define GEN_INT_STATUS                          0x0044
 #define CRTC_GEN_CNTL                           0x0050
 #define CRTC_EXT_CNTL                           0x0054
 #define DAC_CNTL                                0x0058
-- 
2.13.7