amd64: barely boot into kernel code

1 files changed, 151 insertions, 0 deletions

diff --git a/src/kernel/arch/amd64/ata.c b/src/kernel/arch/amd64/ata.c
new file mode 100644
index 0000000..371730e
--- /dev/null
+++ b/src/kernel/arch/amd64/ata.c
@@ -0,0 +1,151 @@
+#include <kernel/arch/amd64/ata.h>
+#include <kernel/arch/amd64/port_io.h>
+#include <kernel/panic.h>
+#include <stdbool.h>
+
+static struct {
+	enum {
+		DEV_UNKNOWN,
+		DEV_PATA,
+		DEV_PATAPI,
+	} type;
+	uint32_t sectors;
+} ata_drives[4];
+
+enum {
+	DATA   = 0,
+	FEAT   = 1,
+	SCNT   = 2,
+	LBAlo  = 3,
+	LBAmid = 4,
+	LBAhi  = 5,
+	DRV    = 6,
+	CMD    = 7,
+	STATUS = 7,
+
+	/* note: the OSDev wiki uses a different base port for the control port
+	 *       however i can just use this offset and stuff will just work tm */
+	CTRL   = 0x206,
+}; // offsets
+
+// get I/O port base for drive
+static uint16_t ata_iobase(int drive) {
+	bool secondary = drive&2;
+	return secondary ? 0x170 : 0x1F0;
+}
+
+static void ata_400ns(void) {
+	uint16_t base = ata_iobase(0); // doesn't matter
+	for (int i = 0; i < 4; i++)
+		port_in8(base + STATUS);
+}
+
+static void ata_driveselect(int drive, int block) {
+	uint8_t v = 0xE0;
+	if (drive&1) // slave?
+		v |= 0x10; // set drive number bit
+	// TODO account for block
+	port_out8(ata_iobase(drive) + DRV, v);
+}
+
+static void ata_softreset(int drive) {
+	uint16_t iobase = ata_iobase(drive);
+	port_out8(iobase + CTRL, 4);
+	port_out8(iobase + CTRL, 0);
+	ata_400ns();
+
+	uint16_t timeout = 10000;
+	while (--timeout) { // TODO separate polling function
+		uint8_t v = port_in8(iobase + STATUS);
+		if (v & 0x80) continue; // still BSY, continue
+		if (v & 0x40) break; // RDY, break
+		// TODO check for ERR
+	}
+}
+
+static void ata_detecttype(int drive) {
+	ata_softreset(drive);
+	ata_driveselect(drive, 0);
+	ata_400ns();
+	switch (port_in8(ata_iobase(drive) + LBAmid)) {
+		case 0:
+			ata_drives[drive].type = DEV_PATA;
+			break;
+		case 0x14:
+			ata_drives[drive].type = DEV_PATAPI;
+			break;
+		default:
+			ata_drives[drive].type = DEV_UNKNOWN;
+			break;
+	}
+}
+
+static bool ata_identify(int drive) {
+	uint16_t iobase = ata_iobase(drive);
+	uint16_t data[256];
+	uint8_t v;
+
+	ata_driveselect(drive, 0);
+	for (int i = 2; i < 6; i++)
+		port_out8(iobase + i, 0);
+	switch (ata_drives[drive].type) {
+		case DEV_PATA:
+			port_out8(iobase + CMD, 0xEC); // IDENTIFY
+			break;
+		case DEV_PATAPI:
+			port_out8(iobase + CMD, 0xA1); // IDENTIFY PACKET DEVICE
+			break;
+		default: panic_invalid_state();
+	}
+
+	v = port_in8(iobase + STATUS);
+	if (v == 0) return false; // nonexistent drive
+	while (port_in8(iobase + STATUS) & 0x80);
+
+	/* pool until bit 3 (DRQ) or 0 (ERR) is set */
+	while (!((v = port_in8(iobase + STATUS) & 0x9)));
+	if (v & 1) return false; /* ERR was set, bail */
+
+	for (int i = 0; i < 256; i++)
+		data[i] = port_in16(iobase);
+	ata_drives[drive].sectors = data[60] | (data[61] << 16);
+	return true;
+}
+
+void ata_init(void) {
+	for (int i = 0; i < 4; i++) {
+		ata_detecttype(i);
+		if (ata_drives[i].type == DEV_PATA)
+			ata_identify(i);
+	}
+}
+
+bool ata_available(int drive) {
+	return ata_drives[drive].type != DEV_UNKNOWN;
+}
+
+int ata_read(int drive, uint32_t lba, void *buf) {
+	assert(ata_drives[drive].type == DEV_PATA);
+	int iobase = ata_iobase(drive);
+
+	ata_driveselect(drive, lba);
+	port_out8(iobase + FEAT, 0); // supposedly pointless
+	port_out8(iobase + SCNT, 1); // sector count
+	port_out8(iobase + LBAlo, lba);
+	port_out8(iobase + LBAmid, lba >> 8);
+	port_out8(iobase + LBAhi, lba >> 16);
+	port_out8(iobase + CMD, 0x20); // READ SECTORS
+
+	for (;;) { // TODO separate polling function
+		uint8_t v = port_in8(iobase + STATUS);
+		if (v & 0x80) continue; // still BSY, continue
+		if (v & 0x40) break; // RDY, break
+		// TODO check for ERR
+	}
+
+	uint16_t *b = buf;
+	for (int i = 0; i < 256; i++)
+		b[i] = port_in16(iobase);
+
+	return 512;
+}