[PATCH v2 1/3] via-ide: Fix legacy mode emulation

[BALATON Zoltan]

The initial value for BARs were set in reset method for emulating
legacy mode at start but this does not work because PCI code resets
BARs after calling device reset method. Remove this ineffective
default to avoid confusion.

Instead move setting the BARs to a callback on writing the PCI config
regsiter that sets legacy mode (which firmwares needing this mode seem
to do) and fix their values to program it to use legacy port numbers
in this case. This does not fully emulate what the data sheet says
(which is not very clear on this) but it implements enogh to allow
both modes as used by firmwares of machines we emulate.

Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
---
 hw/ide/via.c | 41 ++++++++++++++++++++++++++++++++++++-----
 1 file changed, 36 insertions(+), 5 deletions(-)

diff --git a/hw/ide/via.c b/hw/ide/via.c
index fff23803a6..43e8af8d69 100644
--- a/hw/ide/via.c
+++ b/hw/ide/via.c
@@ -132,11 +132,6 @@ static void via_ide_reset(DeviceState *dev)
     pci_set_word(pci_conf + PCI_STATUS, PCI_STATUS_FAST_BACK |
                  PCI_STATUS_DEVSEL_MEDIUM);
 
-    pci_set_long(pci_conf + PCI_BASE_ADDRESS_0, 0x000001f0);
-    pci_set_long(pci_conf + PCI_BASE_ADDRESS_1, 0x000003f4);
-    pci_set_long(pci_conf + PCI_BASE_ADDRESS_2, 0x00000170);
-    pci_set_long(pci_conf + PCI_BASE_ADDRESS_3, 0x00000374);
-    pci_set_long(pci_conf + PCI_BASE_ADDRESS_4, 0x0000cc01); /* BMIBA: 20-23h 
*/
     pci_set_long(pci_conf + PCI_INTERRUPT_LINE, 0x0000010e);
 
     /* IDE chip enable, IDE configuration 1/2, IDE FIFO Configuration*/
@@ -159,6 +154,41 @@ static void via_ide_reset(DeviceState *dev)
     pci_set_long(pci_conf + 0xc0, 0x00020001);
 }
 
+static void via_ide_cfg_write(PCIDevice *pd, uint32_t addr,
+                              uint32_t val, int len)
+{
+    pci_default_write_config(pd, addr, val, len);
+    /*
+     * Bits 0 and 2 of the PCI programming interface register select between
+     * legacy and native mode for the two IDE channels. We don't emulate this
+     * because we cannot easily switch between ISA and PCI in QEMU so instead
+     * when guest selects legacy mode we set the PCI BARs to legacy ports which
+     * works the same. We also don't care about setting each channel separately
+     * as no guest is known to do or need that. We only do this when BARs are
+     * unset when writing this register as logs from real hardware show that
+     * setting legacy mode after BARs were set it will still use ports set by
+     * BARs not ISA ports (e.g. pegasos2 Linux does this after firmware set
+     * native mode and programmed BARs and calls it non-100% native mode).
+     * But if 0x8a is written righr after reset without setting BARs then we
+     * want legacy ports (this is done by the AmigaOne firmware).
+     */
+    if (addr == PCI_CLASS_PROG && val == 0x8a &&
+        pci_get_long(pd->config + PCI_BASE_ADDRESS_0) ==
+        PCI_BASE_ADDRESS_SPACE_IO) {
+        pci_set_long(pd->config + PCI_BASE_ADDRESS_0, 0x1f0
+                     | PCI_BASE_ADDRESS_SPACE_IO);
+        pci_set_long(pd->config + PCI_BASE_ADDRESS_1, 0x3f6
+                     | PCI_BASE_ADDRESS_SPACE_IO);
+        pci_set_long(pd->config + PCI_BASE_ADDRESS_2, 0x170
+                     | PCI_BASE_ADDRESS_SPACE_IO);
+        pci_set_long(pd->config + PCI_BASE_ADDRESS_3, 0x376
+                     | PCI_BASE_ADDRESS_SPACE_IO);
+        /* BMIBA: 20-23h */
+        pci_set_long(pd->config + PCI_BASE_ADDRESS_4, 0xcc00
+                     | PCI_BASE_ADDRESS_SPACE_IO);
+    }
+}
+
 static void via_ide_realize(PCIDevice *dev, Error **errp)
 {
     PCIIDEState *d = PCI_IDE(dev);
@@ -221,6 +251,7 @@ static void via_ide_class_init(ObjectClass *klass, void 
*data)
     /* Reason: only works as function of VIA southbridge */
     dc->user_creatable = false;
 
+    k->config_write = via_ide_cfg_write;
     k->realize = via_ide_realize;
     k->exit = via_ide_exitfn;
     k->vendor_id = PCI_VENDOR_ID_VIA;
-- 
2.30.9