[SeaBIOS] [PATCH v2] pciinit: Enable default VGA device

[Alex Williamson]

As QEMU gains PCI bridge and PCIe root port support, we won't always
find the VGA device on the root bus.  We therefore need to add support
to find and enable a VGA device and the path to it through the VGA
Enable support in the PCI bridge control register.

Signed-off-by: Alex Williamson <alex.williamson at redhat.com>
---
 src/optionroms.c |    2 +-
 src/pciinit.c    |   45 +++++++++++++++++++++++++++++++++++++++++++++
 src/util.h       |    1 +
 3 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/src/optionroms.c b/src/optionroms.c
index caa2151..ac92613 100644
--- a/src/optionroms.c
+++ b/src/optionroms.c
@@ -213,7 +213,7 @@ run_file_roms(const char *prefix, int isvga, u64 *sources)
  ****************************************************************/
 
 // Verify device is a vga device with legacy address decoding enabled.
-static int
+int
 is_pci_vga(struct pci_device *pci)
 {
     if (pci->class != PCI_CLASS_DISPLAY_VGA)
diff --git a/src/pciinit.c b/src/pciinit.c
index ce0a4cc..eb49a76 100644
--- a/src/pciinit.c
+++ b/src/pciinit.c
@@ -316,6 +316,49 @@ static void pci_bios_init_devices(void)
     }
 }
 
+static void pci_enable_default_vga(void)
+{
+    struct pci_device *pci;
+
+    foreachpci(pci) {
+        if (is_pci_vga(pci)) {
+            dprintf(1, "PCI: Using %02x:%02x.%x for primary VGA\n",
+                    pci_bdf_to_bus(pci->bdf), pci_bdf_to_dev(pci->bdf),
+                    pci_bdf_to_fn(pci->bdf));
+            return;
+        }
+    }
+
+    pci = pci_find_class(PCI_CLASS_DISPLAY_VGA);
+    if (!pci) {
+        dprintf(1, "PCI: No VGA devices found\n");
+        return;
+    }
+
+    dprintf(1, "PCI: Enabling %02x:%02x.%x for primary VGA\n",
+            pci_bdf_to_bus(pci->bdf), pci_bdf_to_dev(pci->bdf),
+            pci_bdf_to_fn(pci->bdf));
+
+    u16 cmd = pci_config_readw(pci->bdf, PCI_COMMAND);
+    cmd |= PCI_COMMAND_IO | PCI_COMMAND_MEMORY;
+    pci_config_writew(pci->bdf, PCI_COMMAND, cmd);
+
+    while (pci->parent) {
+        pci = pci->parent;
+
+        dprintf(1, "PCI: Setting VGA enable on bridge %02x:%02x.%x\n",
+                pci_bdf_to_bus(pci->bdf), pci_bdf_to_dev(pci->bdf),
+                pci_bdf_to_fn(pci->bdf));
+
+        u8 ctrl = pci_config_readb(pci->bdf, PCI_BRIDGE_CONTROL);
+        ctrl |= PCI_BRIDGE_CTL_VGA;
+        pci_config_writeb(pci->bdf, PCI_BRIDGE_CONTROL, ctrl);
+
+        u16 cmd = pci_config_readw(pci->bdf, PCI_COMMAND);
+        cmd |= PCI_COMMAND_IO | PCI_COMMAND_MEMORY;
+        pci_config_writew(pci->bdf, PCI_COMMAND, cmd);
+    }
+}
 
 /****************************************************************
  * Platform device initialization
@@ -804,4 +847,6 @@ pci_setup(void)
     pci_bios_init_devices();
 
     free(busses);
+
+    pci_enable_default_vga();
 }
diff --git a/src/util.h b/src/util.h
index 306a8bf..e1df295 100644
--- a/src/util.h
+++ b/src/util.h
@@ -343,6 +343,7 @@ void vgahook_setup(struct pci_device *pci);
 
 // optionroms.c
 void call_bcv(u16 seg, u16 ip);
+int is_pci_vga(struct pci_device *pci);
 void optionrom_setup(void);
 void vgarom_setup(void);
 void s3_resume_vga(void);