/*
 *  linux/kernel/floppy.c
 *
 *  (C) 1991  Linus Torvalds
 */

/*
 * 02.12.91 - Changed to static variables to indicate need for reset
 * and recalibrate. This makes some things easier (output_byte reset
 * checking etc), and means less interrupt jumping in case of errors,
 * so the code is hopefully easier to understand.
 */

/*
 * This file is certainly a mess. I've tried my best to get it working,
 * but I don't like programming floppies, and I have only one anyway.
 * Urgel. I should check for more errors, and do more graceful error
 * recovery. Seems there are problems with several drives. I've tried to
 * correct them. No promises. 
 */

/*
 * As with hd.c, all routines within this file can (and will) be called
 * by interrupts, so extreme caution is needed. A hardware interrupt
 * handler may not sleep, or a kernel panic will happen. Thus I cannot
 * call "floppy-on" directly, but have to set a special timer interrupt
 * etc.
 *
 * Also, I'm not certain this works on more than 1 floppy. Bugs may
 * abund.
 */

#include <linux/sched.h>
#include <linux/fs.h>
#include <linux/kernel.h>
#include <linux/fdreg.h>
#include <asm/system.h>
#include <asm/io.h>
#include <asm/segment.h>

#define MAJOR_NR 2
#include "blk.h"

static int recalibrate = 0;
static int reset = 0;
static int seek = 0;

extern unsigned char current_DOR;

#define immoutb_p(val,port) \
__asm__("outb %0,%1\n\tjmp 1f\n1:\tjmp 1f\n1:"::"a" ((char) (val)),"i" (port))

#define TYPE(x) ((x)>>2)
#define DRIVE(x) ((x)&0x03)
/*
 * Note that MAX_ERRORS=8 doesn't imply that we retry every bad read
 * max 8 times - some types of errors increase the errorcount by 2,
 * so we might actually retry only 5-6 times before giving up.
 */
#define MAX_ERRORS 8

/*
 * globals used by 'result()'
 */
#define MAX_REPLIES 7
static unsigned char reply_buffer[MAX_REPLIES];
#define ST0 (reply_buffer[0])
#define ST1 (reply_buffer[1])
#define ST2 (reply_buffer[2])
#define ST3 (reply_buffer[3])

/*
 * This struct defines the different floppy types. Unlike minix
 * linux doesn't have a "search for right type"-type, as the code
 * for that is convoluted and weird. I've got enough problems with
 * this driver as it is.
 *
 * The 'stretch' tells if the tracks need to be boubled for some
 * types (ie 360kB diskette in 1.2MB drive etc). Others should
 * be self-explanatory.
 */
static struct floppy_struct {
        unsigned int size, sect, head, track, stretch;
        unsigned char gap,rate,spec1;
} floppy_type[] = {
        {    0, 0,0, 0,0,0x00,0x00,0x00 },      /* no testing */
        {  720, 9,2,40,0,0x2A,0x02,0xDF },      /* 360kB PC diskettes */
        { 2400,15,2,80,0,0x1B,0x00,0xDF },      /* 1.2 MB AT-diskettes */
        {  720, 9,2,40,1,0x2A,0x02,0xDF },      /* 360kB in 720kB drive */
        { 1440, 9,2,80,0,0x2A,0x02,0xDF },      /* 3.5" 720kB diskette */
        {  720, 9,2,40,1,0x23,0x01,0xDF },      /* 360kB in 1.2MB drive */
        { 1440, 9,2,80,0,0x23,0x01,0xDF },      /* 720kB in 1.2MB drive */
        { 2880,18,2,80,0,0x1B,0x00,0xCF },      /* 1.44MB diskette */
};
/*
 * Rate is 0 for 500kb/s, 2 for 300kbps, 1 for 250kbps
 * Spec1 is 0xSH, where S is stepping rate (F=1ms, E=2ms, D=3ms etc),
 * H is head unload time (1=16ms, 2=32ms, etc)
 *
 * Spec2 is (HLD<<1 | ND), where HLD is head load time (1=2ms, 2=4 ms etc)
 * and ND is set means no DMA. Hardcoded to 6 (HLD=6ms, use DMA).
 */

extern void floppy_interrupt(void);
extern char tmp_floppy_area[1024];

/*
 * These are global variables, as that's the easiest way to give
 * information to interrupts. They are the data used for the current
 * request.
 */
static int cur_spec1 = -1;
static int cur_rate = -1;
static struct floppy_struct * floppy = floppy_type;
static unsigned char current_drive = 0;
static unsigned char sector = 0;
static unsigned char head = 0;
static unsigned char track = 0;
static unsigned char seek_track = 0;
static unsigned char current_track = 255;
static unsigned char command = 0;
unsigned char selected = 0;
struct task_struct * wait_on_floppy_select = NULL;

void floppy_deselect(unsigned int nr)
{
        if (nr != (current_DOR & 3))
                printk("floppy_deselect: drive not selected\n\r");
        selected = 0;
        wake_up(&wait_on_floppy_select);
}

/*
 * floppy-change is never called from an interrupt, so we can relax a bit
 * here, sleep etc. Note that floppy-on tries to set current_DOR to point
 * to the desired drive, but it will probably not survive the sleep if
 * several floppies are used at the same time: thus the loop.
 */
int floppy_change(unsigned int nr)
{
repeat:
        floppy_on(nr);
        while ((current_DOR & 3) != nr && selected)
                interruptible_sleep_on(&wait_on_floppy_select);
        if ((current_DOR & 3) != nr)
                goto repeat;
        if (inb(FD_DIR) & 0x80) {
                floppy_off(nr);
                return 1;
        }
        floppy_off(nr);
        return 0;
}

#define copy_buffer(from,to) \
__asm__("cld ; rep ; movsl" \
        ::"c" (BLOCK_SIZE/4),"S" ((long)(from)),"D" ((long)(to)) \
        :"cx","di","si")

static void setup_DMA(void)
{
        long addr = (long) CURRENT->buffer;

        cli();
        if (addr >= 0x100000) {
                addr = (long) tmp_floppy_area;
                if (command == FD_WRITE)
                        copy_buffer(CURRENT->buffer,tmp_floppy_area);
        }
/* mask DMA 2 */
        immoutb_p(4|2,10);
/* output command byte. I don't know why, but everyone (minix, */
/* sanches & canton) output this twice, first to 12 then to 11 */
        __asm__("outb %%al,$12\n\tjmp 1f\n1:\tjmp 1f\n1:\t"
        "outb %%al,$11\n\tjmp 1f\n1:\tjmp 1f\n1:"::
        "a" ((char) ((command == FD_READ)?DMA_READ:DMA_WRITE)));
/* 8 low bits of addr */
        immoutb_p(addr,4);
        addr >>= 8;
/* bits 8-15 of addr */
        immoutb_p(addr,4);
        addr >>= 8;
/* bits 16-19 of addr */
        immoutb_p(addr,0x81);
/* low 8 bits of count-1 (1024-1=0x3ff) */
        immoutb_p(0xff,5);
/* high 8 bits of count-1 */
        immoutb_p(3,5);
/* activate DMA 2 */
        immoutb_p(0|2,10);
        sti();
}

static void output_byte(char byte)
{
        int counter;
        unsigned char status;

        if (reset)
                return;
        for(counter = 0 ; counter < 10000 ; counter++) {
                status = inb_p(FD_STATUS) & (STATUS_READY | STATUS_DIR);
                if (status == STATUS_READY) {
                        outb(byte,FD_DATA);
                        return;
                }
        }
        reset = 1;
        printk("Unable to send byte to FDC\n\r");
}

static int result(void)
{
        int i = 0, counter, status;

        if (reset)
                return -1;
        for (counter = 0 ; counter < 10000 ; counter++) {
                status = inb_p(FD_STATUS)&(STATUS_DIR|STATUS_READY|STATUS_BUSY);
                if (status == STATUS_READY)
                        return i;
                if (status == (STATUS_DIR|STATUS_READY|STATUS_BUSY)) {
                        if (i >= MAX_REPLIES)
                                break;
                        reply_buffer[i++] = inb_p(FD_DATA);
                }
        }
        reset = 1;
        printk("Getstatus times out\n\r");
        return -1;
}

static void bad_flp_intr(void)
{
        CURRENT->errors++;
        if (CURRENT->errors > MAX_ERRORS) {
                floppy_deselect(current_drive);
                end_request(0);
        }
        if (CURRENT->errors > MAX_ERRORS/2)
                reset = 1;
        else
                recalibrate = 1;
}       

/*
 * Ok, this interrupt is called after a DMA read/write has succeeded,
 * so we check the results, and copy any buffers.
 */
static void rw_interrupt(void)
{
        if (result() != 7 || (ST0 & 0xf8) || (ST1 & 0xbf) || (ST2 & 0x73)) {
                if (ST1 & 0x02) {
                        printk("Drive %d is write protected\n\r",current_drive);
                        floppy_deselect(current_drive);
                        end_request(0);
                } else
                        bad_flp_intr();
                do_fd_request();
                return;
        }
        if (command == FD_READ && (unsigned long)(CURRENT->buffer) >= 0x100000)
                copy_buffer(tmp_floppy_area,CURRENT->buffer);
        floppy_deselect(current_drive);
        end_request(1);
        do_fd_request();
}

inline void setup_rw_floppy(void)
{
        setup_DMA();
        do_floppy = rw_interrupt;
        output_byte(command);
        output_byte(head<<2 | current_drive);
        output_byte(track);
        output_byte(head);
        output_byte(sector);
        output_byte(2);         /* sector size = 512 */
        output_byte(floppy->sect);
        output_byte(floppy->gap);
        output_byte(0xFF);      /* sector size (0xff when n!=0 ?) */
        if (reset)
                do_fd_request();
}

/*
 * This is the routine called after every seek (or recalibrate) interrupt
 * from the floppy controller. Note that the "unexpected interrupt" routine
 * also does a recalibrate, but doesn't come here.
 */
static void seek_interrupt(void)
{
/* sense drive status */
        output_byte(FD_SENSEI);
        if (result() != 2 || (ST0 & 0xF8) != 0x20 || ST1 != seek_track) {
                bad_flp_intr();
                do_fd_request();
                return;
        }
        current_track = ST1;
        setup_rw_floppy();
}

/*
 * This routine is called when everything should be correctly set up
 * for the transfer (ie floppy motor is on and the correct floppy is
 * selected).
 */
static void transfer(void)
{
        if (cur_spec1 != floppy->spec1) {
                cur_spec1 = floppy->spec1;
                output_byte(FD_SPECIFY);
                output_byte(cur_spec1);         /* hut etc */
                output_byte(6);                 /* Head load time =6ms, DMA */
        }
        if (cur_rate != floppy->rate)
                outb_p(cur_rate = floppy->rate,FD_DCR);
        if (reset) {
                do_fd_request();
                return;
        }
        if (!seek) {
                setup_rw_floppy();
                return;
        }
        do_floppy = seek_interrupt;
        if (seek_track) {
                output_byte(FD_SEEK);
                output_byte(head<<2 | current_drive);
                output_byte(seek_track);
        } else {
                output_byte(FD_RECALIBRATE);
                output_byte(head<<2 | current_drive);
        }
        if (reset)
                do_fd_request();
}

/*
 * Special case - used after a unexpected interrupt (or reset)
 */
static void recal_interrupt(void)
{
        output_byte(FD_SENSEI);
        if (result()!=2 || (ST0 & 0xE0) == 0x60)
                reset = 1;
        else
                recalibrate = 0;
        do_fd_request();
}

void unexpected_floppy_interrupt(void)
{
        output_byte(FD_SENSEI);
        if (result()!=2 || (ST0 & 0xE0) == 0x60)
                reset = 1;
        else
                recalibrate = 1;
}

static void recalibrate_floppy(void)
{
        recalibrate = 0;
        current_track = 0;
        do_floppy = recal_interrupt;
        output_byte(FD_RECALIBRATE);
        output_byte(head<<2 | current_drive);
        if (reset)
                do_fd_request();
}

static void reset_interrupt(void)
{
        output_byte(FD_SENSEI);
        (void) result();
        output_byte(FD_SPECIFY);
        output_byte(cur_spec1);         /* hut etc */
        output_byte(6);                 /* Head load time =6ms, DMA */
        do_fd_request();
}

/*
 * reset is done by pulling bit 2 of DOR low for a while.
 */
static void reset_floppy(void)
{
        int i;

        reset = 0;
        cur_spec1 = -1;
        cur_rate = -1;
        recalibrate = 1;
        printk("Reset-floppy called\n\r");
        cli();
        do_floppy = reset_interrupt;
        outb_p(current_DOR & ~0x04,FD_DOR);
        for (i=0 ; i<100 ; i++)
                __asm__("nop");
        outb(current_DOR,FD_DOR);
        sti();
}

static void floppy_on_interrupt(void)
{
/* We cannot do a floppy-select, as that might sleep. We just force it */
        selected = 1;
        if (current_drive != (current_DOR & 3)) {
                current_DOR &= 0xFC;
                current_DOR |= current_drive;
                outb(current_DOR,FD_DOR);
                add_timer(2,&transfer);
        } else
                transfer();
}

void do_fd_request(void)
{
        unsigned int block;

        seek = 0;
        if (reset) {
                reset_floppy();
                return;
        }
        if (recalibrate) {
                recalibrate_floppy();
                return;
        }
        INIT_REQUEST;
        floppy = (MINOR(CURRENT->dev)>>2) + floppy_type;
        if (current_drive != CURRENT_DEV)
                seek = 1;
        current_drive = CURRENT_DEV;
        block = CURRENT->sector;
        if (block+2 > floppy->size) {
                end_request(0);
                goto repeat;
        }
        sector = block % floppy->sect;
        block /= floppy->sect;
        head = block % floppy->head;
        track = block / floppy->head;
        seek_track = track << floppy->stretch;
        if (seek_track != current_track)
                seek = 1;
        sector++;
        if (CURRENT->cmd == READ)
                command = FD_READ;
        else if (CURRENT->cmd == WRITE)
                command = FD_WRITE;
        else
                panic("do_fd_request: unknown command");
        add_timer(ticks_to_floppy_on(current_drive),&floppy_on_interrupt);
}

void floppy_init(void)
{
        blk_dev[MAJOR_NR].request_fn = DEVICE_REQUEST;
        set_trap_gate(0x26,&floppy_interrupt);
        outb(inb_p(0x21)&~0x40,0x21);
}