Add PCI initialization in QEMU stdvga

Signed-off-by: Harry Chen <i@harrychen.xyz>

kernel/src/arch/mipsel/board/malta/mod.rs

@@ -31,7 +31,7 @@ pub fn init_serial_early() {
 /// Initialize other board drivers
 pub fn init_driver() {
     // TODO: add possibly more drivers
-    vga::init(0x92050000, 800, 600);
+    vga::init(0xb8000000, 0x92050000, 800, 600);
 }
 
 pub fn probe_fb_info(_width: u32, _height: u32, _depth: u32) -> fb::FramebufferResult {

kernel/src/drivers/gpu/qemu_stdvga.rs

@@ -14,8 +14,40 @@ const VBE_DISPI_INDEX_ENABLE: u16 = 0x04;
 const VGA_AR_PAS: u8 =  0x20;
 const VBE_DISPI_ENABLED: u16 = 0x01;
 
-pub fn init(vga_base: usize, x_res: u16, y_res: u16) {
+const PCIR_COMMAND: u8 = 0x04;
+const PCIM_CMD_PORTEN: u16 = 0x0001;
+const PCIM_CMD_MEMEN: u16 = 0x0002;
 
+
+fn pci_read_config(pci_base: usize, bus: u8, slot: u8, func: u8, offset: u8) -> u16 {
+    // enable access mechanism
+    let data = 0xF0 | (func << 1);
+    write(pci_base + 0xcf8, data);
+    write(pci_base + 0xcfa, bus);
+    // calculate port address
+    let addr: u16 = (0xC000 | ((slot as u16) << 8) | (offset as u16)) & 0xFFFC;
+    // do the actual work
+    read(pci_base + addr as usize)
+}
+
+fn pci_write_config(pci_base: usize, bus: u8, slot: u8, func: u8, offset: u8, value: u16) {
+    // enable access mechanism
+    let data = 0xF0 | (func << 1);
+    write(pci_base + 0xcf8, data);
+    write(pci_base + 0xcfa, bus);
+    // calculate port address
+    let addr: u16 = (0xC000 | ((slot as u16) << 8) | (offset as u16)) & 0xFFFC;
+    // do the actual work
+    write(pci_base + addr as usize, value);
+}
+
+pub fn init(pci_base: usize, vga_base: usize, x_res: u16, y_res: u16) {
+
+    // enable PCI MMIO
+    let pci_state = pci_read_config(pci_base, 0x00, 0x12, 0x00, PCIR_COMMAND);
+    pci_write_config(pci_base, 0x00, 0x12, 0x00, PCIR_COMMAND, pci_state | PCIM_CMD_PORTEN | PCIM_CMD_MEMEN);
+
+    // vga operations
     let vga_write_io = |offset: u16, value: u8| {
         write(vga_base + VGA_MMIO_OFFSET + (offset as usize), value);
     };
@@ -38,4 +70,6 @@ pub fn init(vga_base: usize, x_res: u16, y_res: u16) {
     let vbe_enable = vga_read_vbe(VBE_DISPI_INDEX_ENABLE) | VBE_DISPI_ENABLED;
     vga_write_vbe(VBE_DISPI_INDEX_ENABLE, vbe_enable);
 
-}
+    println!("QEMU STDVGA driver initialized @ {:x}", vga_base);
+
+}