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FMC DEL 1ns 4cha - Software
Commit b2b9b111 authored by Alessandro Rubini's avatar Alessandro Rubini
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kernel/fd-zio: implement DCR_NO_FINE 

This old FIXME is now fixed. Unfortunately the calculation involved is
very boring, given the range of values we deal with.

With this in place, we can now generate a 10MHz square wave and
simulate the inputs for a WR grandmaster.
Signed-off-by: Alessandro Rubini's avatarAlessandro Rubini <rubini@gnudd.com>
parent a8085ff0
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Showing with 37 additions and 4 deletions
kernel/fd-zio.c
View file @ b2b9b111
......@@ -425,6 +425,7 @@ void fd_apply_offset(uint32_t *a, int32_t off_pico)
/* Internal output engine */
static void __fd_zio_output(struct fd_dev *fd, int index1_4, uint32_t *attrs)
{
struct timespec delta, width;
int ch = index1_4 - 1;
int mode = attrs[FD_ATTR_OUT_MODE];
int rep = attrs[FD_ATTR_OUT_REP];
......@@ -473,12 +474,44 @@ static void __fd_zio_output(struct fd_dev *fd, int index1_4, uint32_t *attrs)
* For narrowly spaced pulses, we don't have enough time to reload
* the tap number into the corresponding SY89295.
* Therefore, the width/spacing resolution is limited to 4 ns.
* We put the threshold at 200ns ==> coarse == 25
* We put the threshold at 200ns, i.e. when coarse == 25.
*
* Trivially it would be
* if((delta_ps - width_ps) < 200000 || (width_ps < 200000))
* dcr |= FD_DCR_NO_FINE;
*
* Most likely the calculation below fails with negatives, but
* with negative spacing we get no pulses, and fine is irrelevant
*/
delta.tv_sec = attrs[FD_ATTR_OUT_DELTA_L];
delta.tv_nsec = attrs[FD_ATTR_OUT_DELTA_COARSE] * 8;
width.tv_sec = ((uint64_t)(attrs[FD_ATTR_OUT_END_H]) << 32
| attrs[FD_ATTR_OUT_END_L])
- ((uint64_t)(attrs[FD_ATTR_OUT_START_H]) << 32
| attrs[FD_ATTR_OUT_START_L]);
if (attrs[FD_ATTR_OUT_END_COARSE] > attrs[FD_ATTR_OUT_START_COARSE]) {
width.tv_nsec = 8 * attrs[FD_ATTR_OUT_END_COARSE]
- 8 * attrs[FD_ATTR_OUT_START_COARSE];
} else {
width.tv_sec--;
width.tv_nsec = NSEC_PER_SEC
- 8 * attrs[FD_ATTR_OUT_START_COARSE]
+ 8 * attrs[FD_ATTR_OUT_END_COARSE];
}
/* delta = delta - width (i.e.: delta is the low-signal width */
delta.tv_sec -= width.tv_sec;
if (delta.tv_nsec > width.tv_nsec) {
delta.tv_nsec -= width.tv_nsec;
} else {
delta.tv_sec--;
delta.tv_nsec = NSEC_PER_SEC - width.tv_nsec + delta.tv_nsec;
}
/* finally check */
if (width.tv_sec == 0 && width.tv_nsec < 200)
dcr |= FD_DCR_NO_FINE;;
if (delta.tv_sec == 0 && delta.tv_nsec < 200)
dcr |= FD_DCR_NO_FINE;;
/* FIXME: if((delta_ps - width_ps) < 200000 ||
(width_ps < 200000)) dcr = FD_DCR_NO_FINE; */
//dcr |= FD_DCR_NO_FINE;
fd_ch_writel(fd, ch, dcr | FD_DCR_UPDATE, FD_REG_DCR);
fd_ch_writel(fd, ch, dcr | FD_DCR_ENABLE, FD_REG_DCR);
......
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