xv6/ide.c

// Simple PIO-based (non-DMA) IDE driver code.

#include "types.h"
#include "defs.h"
#include "param.h"
#include "memlayout.h"
#include "mmu.h"
#include "proc.h"
#include "x86.h"
#include "traps.h"
#include "spinlock.h"
#include "sleeplock.h"
#include "fs.h"
#include "buf.h"

#define SECTOR_SIZE   512
#define IDE_BSY       0x80
#define IDE_DRDY      0x40
#define IDE_DF        0x20
#define IDE_ERR       0x01

#define IDE_CMD_READ  0x20
#define IDE_CMD_WRITE 0x30
#define IDE_CMD_RDMUL 0xc4
#define IDE_CMD_WRMUL 0xc5

// idequeue points to the buf now being read/written to the disk.
// idequeue->qnext points to the next buf to be processed.
// You must hold idelock while manipulating queue.

static struct spinlock idelock;
static struct buf *idequeue;

static int havedisk1;
static void idestart(struct buf*);

// Wait for IDE disk to become ready.
static int idewait(int checkerr) {
    int r;

    while (((r = inb(0x1f7)) & (IDE_BSY | IDE_DRDY)) != IDE_DRDY) {
        ;
    }
    if (checkerr && (r & (IDE_DF | IDE_ERR)) != 0) {
        return -1;
    }
    return 0;
}

void ideinit(void) {
    int i;

    initlock(&idelock, "ide");
    ioapicenable(IRQ_IDE, ncpu - 1);
    idewait(0);

    // Check if disk 1 is present
    outb(0x1f6, 0xe0 | (1 << 4));
    for (i = 0; i < 1000; i++) {
        if (inb(0x1f7) != 0) {
            havedisk1 = 1;
            break;
        }
    }

    // Switch back to disk 0.
    outb(0x1f6, 0xe0 | (0 << 4));
}

// Start the request for b.  Caller must hold idelock.
static void idestart(struct buf *b) {
    if (b == 0) {
        panic("idestart");
    }
    if (b->blockno >= FSSIZE) {
        panic("incorrect blockno");
    }
    int sector_per_block =  BSIZE / SECTOR_SIZE;
    int sector = b->blockno * sector_per_block;
    int read_cmd = (sector_per_block == 1) ? IDE_CMD_READ :  IDE_CMD_RDMUL;
    int write_cmd = (sector_per_block == 1) ? IDE_CMD_WRITE : IDE_CMD_WRMUL;

    if (sector_per_block > 7) {
        panic("idestart");
    }

    idewait(0);
    outb(0x3f6, 0);  // generate interrupt
    outb(0x1f2, sector_per_block);  // number of sectors
    outb(0x1f3, sector & 0xff);
    outb(0x1f4, (sector >> 8) & 0xff);
    outb(0x1f5, (sector >> 16) & 0xff);
    outb(0x1f6, 0xe0 | ((b->dev & 1) << 4) | ((sector >> 24) & 0x0f));
    if (b->flags & B_DIRTY) {
        outb(0x1f7, write_cmd);
        outsl(0x1f0, b->data, BSIZE / 4);
    }
    else {
        outb(0x1f7, read_cmd);
    }
}

// Interrupt handler.
void ideintr(void) {
    struct buf *b;

    // First queued buffer is the active request.
    acquire(&idelock);

    if ((b = idequeue) == 0) {
        release(&idelock);
        return;
    }
    idequeue = b->qnext;

    // Read data if needed.
    if (!(b->flags & B_DIRTY) && idewait(1) >= 0) {
        insl(0x1f0, b->data, BSIZE / 4);
    }

    // Wake process waiting for this buf.
    b->flags |= B_VALID;
    b->flags &= ~B_DIRTY;
    wakeup(b);

    // Start disk on next buf in queue.
    if (idequeue != 0) {
        idestart(idequeue);
    }

    release(&idelock);
}


// Sync buf with disk.
// If B_DIRTY is set, write buf to disk, clear B_DIRTY, set B_VALID.
// Else if B_VALID is not set, read buf from disk, set B_VALID.
void iderw(struct buf *b) {
    struct buf **pp;

    if (!holdingsleep(&b->lock)) {
        panic("iderw: buf not locked");
    }
    if ((b->flags & (B_VALID | B_DIRTY)) == B_VALID) {
        panic("iderw: nothing to do");
    }
    if (b->dev != 0 && !havedisk1) {
        panic("iderw: ide disk 1 not present");
    }

    acquire(&idelock);  //DOC:acquire-lock

    // Append b to idequeue.
    b->qnext = 0;
    for (pp = &idequeue; *pp; pp = &(*pp)->qnext) { //DOC:insert-queue
        ;
    }
    *pp = b;

    // Start disk if necessary.
    if (idequeue == b) {
        idestart(b);
    }

    // Wait for request to finish.
    while ((b->flags & (B_VALID | B_DIRTY)) != B_VALID) {
        sleep(b, &idelock);
    }

    release(&idelock);
}