xv6/ide.c
rtm 902b13f5d6 simplify ide queuing
nits in comments
2007-08-24 19:32:36 +00:00

157 lines
3.2 KiB
C

// Simple PIO-based (non-DMA) IDE driver code.
#include "types.h"
#include "param.h"
#include "mmu.h"
#include "proc.h"
#include "defs.h"
#include "x86.h"
#include "traps.h"
#include "spinlock.h"
#include "buf.h"
#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
// IDE request queue.
// ide_queue points to the buf now being read/written to the disk.
// ide_queue->qnext points to the next buf to be processed.
// Must hold ide_lock while manipulating queue.
static struct spinlock ide_lock;
static struct buf *ide_queue;
static int disk_1_present;
static int ide_probe_disk1(void);
static void ide_start_request();
//PAGEBREAK: 10
// Wait for IDE disk to become ready.
static int
ide_wait_ready(int check_error)
{
int r;
while(((r = inb(0x1F7)) & (IDE_BSY|IDE_DRDY)) != IDE_DRDY)
;
if(check_error && (r & (IDE_DF|IDE_ERR)) != 0)
return -1;
return 0;
}
void
ide_init(void)
{
initlock(&ide_lock, "ide");
irq_enable(IRQ_IDE);
ioapic_enable(IRQ_IDE, ncpu - 1);
ide_wait_ready(0);
disk_1_present = ide_probe_disk1();
}
// Probe to see if disk 1 exists (we assume disk 0 exists).
static int
ide_probe_disk1(void)
{
int r, x;
// wait for Device 0 to be ready
ide_wait_ready(0);
// switch to Device 1
outb(0x1F6, 0xE0 | (1<<4));
// check for Device 1 to be ready for a while
for(x = 0; x < 1000 && (r = inb(0x1F7)) == 0; x++)
;
// switch back to Device 0
outb(0x1F6, 0xE0 | (0<<4));
return x < 1000;
}
// Interrupt handler - wake up the request that just finished.
void
ide_intr(void)
{
acquire(&ide_lock);
if(ide_queue){
//cprintf("intr %x\n", ide_queue);
if((ide_queue->flags & B_WRITE) == 0)
if(ide_wait_ready(1) >= 0)
insl(0x1F0, ide_queue->data, 512/4);
ide_queue->done = 1;
wakeup(ide_queue);
ide_queue = ide_queue->qnext;
ide_start_request();
} else {
cprintf("stray ide interrupt\n");
}
release(&ide_lock);
}
// Start the next request in the queue.
// Caller must hold ide_lock.
static void
ide_start_request (void)
{
if(ide_queue){
ide_wait_ready(0);
//cprintf("start %x\n", ide_queue);
outb(0x3f6, 0); // generate interrupt
outb(0x1F2, 1); // number of sectors
outb(0x1F3, ide_queue->sector & 0xFF);
outb(0x1F4, (ide_queue->sector >> 8) & 0xFF);
outb(0x1F5, (ide_queue->sector >> 16) & 0xFF);
outb(0x1F6, 0xE0 |
((ide_queue->dev & 1)<<4) |
((ide_queue->sector>>24)&0x0F));
if(ide_queue->flags & B_WRITE){
outb(0x1F7, IDE_CMD_WRITE);
outsl(0x1F0, ide_queue->data, 512/4);
} else {
outb(0x1F7, IDE_CMD_READ);
}
}
}
//PAGEBREAK: 30
// Queue up a disk operation and wait for it to finish.
// b must have B_BUSY set.
void
ide_rw(struct buf *b)
{
struct buf **pp;
if((b->dev & 0xff) && !disk_1_present)
panic("ide disk 1 not present");
acquire(&ide_lock);
b->done = 0;
b->qnext = 0;
// cprintf("enqueue %x %x\n", b, ide_queue);
// append b to ide_queue
pp = &ide_queue;
while(*pp)
pp = &(*pp)->qnext;
*pp = b;
if(ide_queue == b)
ide_start_request();
while(!b->done)
sleep(b, &ide_lock);
release(&ide_lock);
}