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Implement asynchronous operation delays between seek/head/read/write
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Also implement the pre- and post-write delays required by many floppy
drive specs.

Refs keirf/greaseweazle#491
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@keirf
keirf committed Sep 23, 2024
1 parent 2b1c541 commit d45f424
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Showing 2 changed files with 85 additions and 8 deletions.
2 changes: 2 additions & 0 deletions inc/cdc_acm_protocol.h
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Original file line number Diff line number Diff line change
Expand Up @@ -226,6 +226,8 @@ struct packed gw_delay {
uint16_t seek_settle; /* msec */
uint16_t motor_delay; /* msec */
uint16_t watchdog; /* msec */
uint16_t pre_write; /* min. usec since previous head change */
uint16_t post_write; /* min. usec to next write/step/head-change */
};

/* CMD_SWITCH_FW_MODE */
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91 changes: 83 additions & 8 deletions src/floppy.c
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Original file line number Diff line number Diff line change
Expand Up @@ -24,8 +24,17 @@
#define sample_us(x) ((x) * SAMPLE_MHZ)
#define time_from_samples(x) udiv64((uint64_t)(x) * TIME_MHZ, SAMPLE_MHZ)

#define write_pin(pin, level) \
gpio_write_pin(gpio_##pin, pin_##pin, level ? O_TRUE : O_FALSE)
/* Track and modify states of output pins. */
static struct {
bool_t dir;
bool_t step;
bool_t wgate;
bool_t head;
} pins;
#define read_pin(pin) pins.pin
#define write_pin(pin, level) ({ \
gpio_write_pin(gpio_##pin, pin_##pin, level ? O_TRUE : O_FALSE); \
pins.pin = level; })

static int bus_type = -1;
static int unit_nr = -1;
Expand All @@ -42,7 +51,9 @@ static const struct gw_delay factory_delay_params = {
.step_delay = 10000,
.seek_settle = 15,
.motor_delay = 750,
.watchdog = 10000
.watchdog = 10000,
.pre_write = 100,
.post_write = 1000
};

extern uint8_t u_buf[];
Expand Down Expand Up @@ -125,6 +136,43 @@ static enum {
static uint32_t u_cons, u_prod;
#define U_MASK(x) ((x)&(U_BUF_SZ-1))

static struct {
struct timer timer;
unsigned int mask;
#define DELAY_read (1u<<0)
#define DELAY_write (1u<<1)
#define DELAY_seek (1u<<2)
#define DELAY_head (1u<<3)
} op_delay;
static void op_delay_timer(void *unused);

/* Delay specified operation(s) by specified number of microseconds. */
static void op_delay_async(unsigned int mask, unsigned int usec)
{
time_t deadline;

/* Very long delays fall back to synchronous wait. */
if (usec > 1000000u) {
delay_us(usec);
return;
}

deadline = time_now() + time_us(usec);
timer_cancel(&op_delay.timer);
if ((op_delay.mask != 0) &&
(time_diff(op_delay.timer.deadline, deadline) < 0))
deadline = op_delay.timer.deadline;
op_delay.mask |= mask;
timer_set(&op_delay.timer, deadline);
}

/* Wait for specified operation(s) to be permitted. */
static void op_delay_wait(unsigned int mask)
{
while (op_delay.mask & mask)
cpu_relax();
}

static void drive_deselect(void)
{
int pin = -1;
Expand Down Expand Up @@ -407,6 +455,8 @@ static uint8_t floppy_seek(int cyl)
return ACK_NO_UNIT;
u = &unit[unit_nr];

op_delay_wait(DELAY_seek);

if (!u->initialised) {
uint8_t rc = floppy_seek_initialise(u);
if (rc != ACK_OKAY)
Expand All @@ -433,7 +483,8 @@ static uint8_t floppy_seek(int cyl)

flippy_trk0_sensor_enable();

delay_ms(delay_params.seek_settle);
op_delay_async(DELAY_read | DELAY_write | DELAY_seek,
delay_params.seek_settle * 1000u);
u->cyl = cyl;

return ACK_OKAY;
Expand Down Expand Up @@ -468,8 +519,12 @@ static uint8_t floppy_noclick_step(void)
static void floppy_flux_end(void)
{
/* Turn off write pins. */
write_pin(wgate, FALSE);
configure_pin(wdata, GPO_bus);
if (read_pin(wgate)) {
write_pin(wgate, FALSE);
configure_pin(wdata, GPO_bus);
op_delay_async(DELAY_write | DELAY_seek | DELAY_head,
delay_params.post_write);
}

/* Turn off timers. */
tim_rdata->ccer = 0;
Expand Down Expand Up @@ -589,6 +644,9 @@ void floppy_init(void)
IRQx_set_prio(irq_index, INDEX_IRQ_PRI);
IRQx_enable(irq_index);

op_delay.mask = 0;
timer_init(&op_delay.timer, op_delay_timer, NULL);

delay_params = factory_delay_params;

_set_bus_type(BUS_NONE);
Expand Down Expand Up @@ -722,6 +780,8 @@ static void rdata_encode_flux(void)

static uint8_t floppy_read_prep(const struct gw_read_flux *rf)
{
op_delay_wait(DELAY_read);

/* Prepare Timer & DMA. */
dma_rdata.mar = (uint32_t)(unsigned long)dma.buf;
dma_rdata.ndtr = ARRAY_SIZE(dma.buf);
Expand Down Expand Up @@ -1097,6 +1157,8 @@ static void floppy_write_wait_data(void)
&& !write_finished)
return;

op_delay_wait(DELAY_write);

floppy_state = ST_write_flux_wait_index;
flux_op.start = time_now();

Expand Down Expand Up @@ -1215,6 +1277,8 @@ static void floppy_write_drain(void)

static uint8_t floppy_erase_prep(const struct gw_erase_flux *ef)
{
op_delay_wait(DELAY_write);

if (get_wrprot() == LOW)
return ACK_WRPROT;

Expand All @@ -1232,7 +1296,7 @@ static void floppy_erase(void)
if (time_since(flux_op.end) < 0)
return;

write_pin(wgate, FALSE);
floppy_flux_end();

/* ACK with Status byte. */
u_buf[0] = flux_op.status;
Expand Down Expand Up @@ -1496,7 +1560,11 @@ static void process_command(void)
uint8_t head = u_buf[2];
if ((len != 3) || (head > 1))
goto bad_command;
write_pin(head, head);
if (read_pin(head) != head) {
op_delay_wait(DELAY_head);
write_pin(head, head);
op_delay_async(DELAY_write, delay_params.pre_write);
}
break;
}
case CMD_SET_PARAMS: {
Expand Down Expand Up @@ -1785,6 +1853,13 @@ static void index_timer(void *unused)
timer_set(&index.timer, now + INDEX_TIMER_PERIOD);
}

static void op_delay_timer(void *unused)
{
while (time_diff(time_now(), op_delay.timer.deadline) > 0)
cpu_relax();
op_delay.mask = 0;
}

/*
* Local variables:
* mode: C
Expand Down

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