Date: Sun, 12 Dec 1999 13:06:57 +0900 From: Seigo Tanimura <tanimura@r.dl.itc.u-tokyo.ac.jp> To: current@freebsd.org, gandalf@vilnya.demon.co.uk Cc: Seigo Tanimura <tanimura@r.dl.itc.u-tokyo.ac.jp> Subject: Re: The secondary buffer in pcm channel for DSPs with small DMA buffers Message-ID: <14419.8033.52078.72159A@silver.carrots.uucp.r.dl.itc.u-tokyo.ac.jp> In-Reply-To: In your message of "Sat, 11 Dec 1999 18:55:38 %2B0900" <14418.8090.86742.72159A@silver.carrots.uucp.r.dl.itc.u-tokyo.ac.jp> References: <14418.8090.86742.72159A@silver.carrots.uucp.r.dl.itc.u-tokyo.ac.jp>
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[-- Attachment #1 --]
On Sat, 11 Dec 1999 18:55:38 +0900,
Seigo Tanimura <tanimura@r.dl.itc.u-tokyo.ac.jp> said:
Seigo> My CS4614 has got only 4KB of the DMA buffer, frequently failing to
Seigo> play pcm blocks continuously. The following patch adds the secondary
Seigo> pcm channel buffers with the size independent from that of a DSP. The
Seigo> patch works quite well with mpg123 and x11amp. For those who has the
Seigo> similar problem could you please try that?
A few fixes and updates have been added, including recovery from DMA
underflow. The value returned from chn_getptr() in chn_checkunderflow()
may get a lag when we get back to chn_write(), which is likely to
cause noise.
Consider a DMA buffer capable to hold 10 samples, as shown below.
DMA buffer 0123456789
Sample ----------
Buffer Pointer R---------
F---------
Playing Point P---------
Since a DMA keeps running even after underflow occurs, P may advance,
leaving F.
DMA buffer 0123456789
Sample ----------
Buffer Pointer R---------
F---------
Playing Point --P-------
If we fill the buffer with new samples in this situation, play begins
from somewhere in the middle of the samples. In the case shown below,
the sample c is the first one to be played. The sample a and b are
played after j, causing noise.
DMA buffer 0123456789
Sample abcdefghij
Buffer Pointer R---------
F---------
Playing Point --P------- --> cdefghijab
In order to avoid the lag, we can advance F upon underflow. A quarter
of the DMA buffer size would be fair.
DMA buffer 0123456789
Sample --abcdefgh
Buffer Pointer R---------
--F-------
Playing Point --P------- --> abcdefgh
With the following patch, x11amp and mpg123 play with no noise even
under an extremely heavy load of more than 50 :)
[-- Attachment #2 --]
Index: channel.c
===================================================================
RCS file: /home/ncvs/src/sys/dev/sound/pcm/channel.c,v
retrieving revision 1.9
diff -u -r1.9 channel.c
--- channel.c 1999/12/05 19:09:12 1.9
+++ channel.c 1999/12/12 03:46:41
@@ -131,9 +131,8 @@
}
/*
- * chn_dmadone() updates pointers and wakes up any process sleeping
- * or waiting on a select().
- * Must be called at spltty().
+ * chn_dmadone() updates pointers and wakes up any process waiting
+ * on a select(). Must be called at spltty().
*/
static void
chn_dmadone(pcm_channel *c)
@@ -142,12 +141,25 @@
chn_dmaupdate(c);
if (ISA_DMA(b)) chn_isadmabounce(c); /* sync bounce buffer */
- wakeup(b);
b->int_count++;
if (b->sel.si_pid && chn_polltrigger(c)) selwakeup(&b->sel);
}
/*
+ * chn_dmawakeup() wakes up any process sleeping. Separated from
+ * chn_dma_done() so that wakeup occurs only when feed from a
+ * secondary buffer to a DMA buffer takes place. Must be called
+ * at spltty().
+ */
+static void
+chn_dmawakeup(pcm_channel *c)
+{
+ snd_dbuf *b = &c->buffer;
+
+ wakeup(b);
+}
+
+/*
* chn_dmaupdate() tracks the status of a dma transfer,
* updating pointers. It must be called at spltty().
*
@@ -181,8 +193,9 @@
}
/*
- * Check channel for underflow occured, reset DMA buffer in case of
- * underflow. It must be called at spltty().
+ * Check channel for underflow occured. Reset DMA buffer in case of
+ * underflow, so that new data can go into the buffer. It must be
+ * called at spltty().
*/
static void
chn_checkunderflow(pcm_channel *c)
@@ -191,9 +204,19 @@
if (b->underflow) {
DEB(printf("Clear underflow condition\n"));
- b->rp = b->fp = chn_getptr(c);
- b->rl = 0;
- b->fl = b->bufsize;
+ /*
+ * The DMA keeps running even after underflow occurs.
+ * Hence the value returned by chn_getptr() here soon
+ * gets a lag when we get back to chn_write(). Although
+ * there are no easy and precise methods to figure out
+ * the lag, a quarter of b->bufsize would be a fair
+ * choice, provided that a DMA interrupt generates upon
+ * each transfer of a half b->bufsize.
+ */
+ b->rp = chn_getptr(c);
+ b->fp = (b->rp + b->bufsize / 4) % b->bufsize;
+ b->rl = b->bufsize / 4;
+ b->fl = b->bufsize - b->rl;
b->underflow=0;
} else {
chn_dmaupdate(c);
@@ -201,6 +224,70 @@
}
/*
+ * Feeds new data to the write dma buffer. Can be called in the bottom half.
+ * Hence must be called at spltty.
+ */
+static int
+chn_wrfeed(pcm_channel *c)
+{
+ snd_dbuf *b = &c->buffer;
+ snd_dbuf *bs = &c->buffer2nd;
+ int a, l, lacc;
+
+ /* ensure we always have a whole number of samples */
+ a = (1 << c->align) - 1;
+ lacc = 0;
+ /* Don't allow write unaligned data */
+ while (bs->rl > a && b->fl > a) {
+ /* ensure we always have a whole number of samples */
+ l = min(min(bs->rl, bs->bufsize - bs->rp), min(b->fl, b->bufsize - b->fp)) & ~a;
+ if (l == 0)
+ return lacc;
+ /* Move the samples, update the markers and pointers. */
+ bcopy(bs->buf + bs->rp, b->buf + b->fp, l);
+ bs->fl += l;
+ bs->rl -= l;
+ bs->rp = (bs->rp + l) % bs->bufsize;
+ b->rl += l;
+ b->fl -= l;
+ b->fp = (b->fp + l) % b->bufsize;
+ /* Accumulate the total bytes of the moved samples. */
+ lacc += l;
+ }
+
+ return lacc;
+}
+
+/* Feeds new data to the secondary write buffer. */
+static int
+chn_wrfeed2nd(pcm_channel *c, struct uio *buf)
+{
+ snd_dbuf *bs = &c->buffer2nd;
+ int l, w, wacc;
+
+ /* ensure we always have a whole number of samples */
+ wacc = 0;
+ while (buf->uio_resid > 0 && bs->fl > 0) {
+ /*
+ * The size of the data to move here does not have to be
+ * aligned. We take care of it upon moving the data to a
+ * DMA buffer.
+ */
+ l = min(bs->fl, bs->bufsize - bs->fp);
+ /* Move the samples, update the markers and pointers. */
+ w = c->feeder->feed(c->feeder, c, bs->buf + bs->fp, l, buf);
+ if (w == 0) panic("no feed");
+ bs->rl += w;
+ bs->fl -= w;
+ bs->fp = (bs->fp + w) % bs->bufsize;
+ /* Accumulate the total bytes of the moved samples. */
+ wacc += w;
+ }
+
+ return wacc;
+}
+
+/*
* Write interrupt routine. Can be called from other places (e.g.
* to start a paused transfer), but with interrupts disabled.
*/
@@ -222,7 +309,18 @@
* needed when doing stereo and 16-bit.
*/
if (c->flags & CHN_F_MAPPED) start = c->flags & CHN_F_TRIGGERED;
- else start = (b->rl >= DMA_ALIGN_THRESHOLD && !(c->flags & CHN_F_ABORTING));
+ else {
+ /*
+ * Fill up the DMA buffer. This may result in making new
+ * free space in the secondary buffer, thus we can wake up
+ * the top half if feed occurs.
+ */
+ if (chn_wrfeed(c) > 0) {
+ chn_dmawakeup(c);
+ while(chn_wrfeed(c) > 0);
+ }
+ start = (b->rl >= DMA_ALIGN_THRESHOLD && !(c->flags & CHN_F_ABORTING));
+ }
if (start) {
int l;
chn_dmaupdate(c);
@@ -237,13 +335,13 @@
/* Start DMA operation */
b->dl = c->blocksize ; /* record new transfer size */
chn_trigger(c, PCMTRIG_START);
- } else if (b->dl != l) {
+ }
+ if (b->dl != l)
/*
* we are near to underflow condition, so to prevent
- * audio 'clicks' clear next 1.5*dl bytes
+ * audio 'clicks' clear next b->fl bytes
*/
- chn_clearbuf(c, (b->dl*3)/2);
- }
+ chn_clearbuf(c, b->fl);
} else {
/* cannot start a new dma transfer */
DEB(printf("cannot start wr-dma flags 0x%08x rp %d rl %d\n",
@@ -274,10 +372,9 @@
int
chn_write(pcm_channel *c, struct uio *buf)
{
- int a, l, w, timeout, ret = 0, rc;
+ int ret = 0, timeout;
long s;
snd_dbuf *b = &c->buffer;
- int threshold, maxthreshold, minthreshold;
if (c->flags & CHN_F_WRITING) {
/* This shouldn't happen and is actually silly
@@ -286,57 +383,39 @@
tsleep(&s, PZERO, "pcmwrW", hz);
return EBUSY;
}
- a = (1 << c->align) - 1;
- maxthreshold = (b->dl / 4 + a) & ~a;
- minthreshold = a;
c->flags |= CHN_F_WRITING;
+ /*
+ * Fill up the secondary and DMA buffer.
+ * chn_wrfeed*() takes care of the alignment.
+ */
s = spltty();
+ /* Check for underflow before writing into the buffers. */
chn_checkunderflow(c);
- splx(s);
- while ((buf->uio_resid + c->smegcnt) > minthreshold ) { /* Don't allow write unaligned data */
- threshold = min((buf->uio_resid + c->smegcnt), maxthreshold);
- if (b->fl < threshold) {
- if (c->flags & CHN_F_NBIO) {
- ret = -1;
- break;
- }
- timeout = (buf->uio_resid >= b->dl)? hz : 1;
- rc = tsleep(b, PRIBIO | PCATCH, "pcmwr", timeout);
- if (rc == 0 || rc == EWOULDBLOCK) {
- s = spltty();
- chn_checkunderflow(c);
- splx(s);
- if (b->fl < minthreshold) continue; /* write only alligned chunk of data */
- } else {
-#if 0
- if (ret == EINTR) chn_abort(c);
-#endif
- ret = rc;
- break;
- }
- }
- /* ensure we always have a whole number of samples */
- l = min(b->fl, b->bufsize - b->fp) & ~a;
- if (l == 0) continue;
- w = c->feeder->feed(c->feeder, c, b->buf + b->fp, l, buf);
- KASSERT(w, ("chn_write: no feed"));
- s = spltty();
- b->rl += w;
- b->fl -= w;
- b->fp = (b->fp + w) % b->bufsize;
- splx(s);
- DEB(if(1) printf("write %d bytes fp %d rl %d\n",w ,b->fp, b->rl));
- if (!b->dl) chn_stintr(c);
- }
- if ((ret == 0) && (buf->uio_resid > 0)) {
- s = spltty();
- l = buf->uio_resid;
- KASSERT( (c->smegcnt + l) < SMEGBUFSZ, ("resid overflow %d", l));
- uiomove(c->smegbuf + c->smegcnt, l, buf);
- c->smegcnt += l;
- splx(s);
- }
+ while (chn_wrfeed2nd(c, buf) > 0 || chn_wrfeed(c) > 0);
+ /* Start playing if not yet. */
+ if (b->rl && !b->dl) chn_wrintr(c);
+ if (!(c->flags & CHN_F_NBIO)) {
+ /* Wait until all samples are played in blocking mode. */
+ while (buf->uio_resid > 0) {
+ splx(s);
+ /* Wait for new free space to write new pcm samples. */
+ timeout = (buf->uio_resid >= b->dl)? hz / 20 : 1;
+ ret = tsleep(b, PRIBIO | PCATCH, "pcmwr", timeout);
+ s = spltty();
+#if notdef
+ if (ret == EINTR) chn_abort(c);
+#endif /* notdef */
+ if (ret == EINTR || ret == ERESTART) break;
+ /* Check for underflow before writing into the buffers. */
+ chn_checkunderflow(c);
+ /* Fill up the buffers with new pcm data. */
+ while (chn_wrfeed2nd(c, buf) > 0 || chn_wrfeed(c) > 0);
+ /* Start playing if necessary. */
+ if (b->rl && !b->dl) chn_wrintr(c);
+ }
+ }
c->flags &= ~CHN_F_WRITING;
+ splx(s);
return (ret > 0)? ret : 0;
}
@@ -370,6 +449,65 @@
*/
+/*
+ * Feed new data from the read buffer. Can be called in the bottom half.
+ * Hence must be called at spltty.
+ */
+static int
+chn_rdfeed(pcm_channel *c)
+{
+ snd_dbuf *b = &c->buffer;
+ snd_dbuf *bs = &c->buffer2nd;
+ int l, lacc;
+
+ /* ensure we always have a whole number of samples */
+ lacc = 0;
+ while (bs->fl >= DMA_ALIGN_THRESHOLD && b->rl >= DMA_ALIGN_THRESHOLD) {
+ l = min(min(bs->fl, bs->bufsize - bs->fp), min(b->rl, b->bufsize - b->rp)) & DMA_ALIGN_MASK;
+ /* Move the samples, update the markers and pointers. */
+ bcopy(b->buf + b->rp, bs->buf + bs->fp, l);
+ bs->fl -= l;
+ bs->rl += l;
+ bs->fp = (bs->fp + l) % bs->bufsize;
+ b->rl -= l;
+ b->fl += l;
+ b->rp = (b->rp + l) % b->bufsize;
+ /* Accumulate the total bytes of the moved samples. */
+ lacc += l;
+ }
+
+ return lacc;
+}
+
+/* Feeds new data from the secondary read buffer. */
+static int
+chn_rdfeed2nd(pcm_channel *c, struct uio *buf)
+{
+ snd_dbuf *bs = &c->buffer2nd;
+ int l, w, wacc;
+
+ /* ensure we always have a whole number of samples */
+ wacc = 0;
+ while (buf->uio_resid > 0 && bs->rl > 0) {
+ /*
+ * The size of the data to move here does not have to be
+ * aligned. We take care of it upon moving the data to a
+ * DMA buffer.
+ */
+ l = min(bs->rl, bs->bufsize - bs->rp);
+ /* Move the samples, update the markers and pointers. */
+ w = c->feeder->feed(c->feeder, c, bs->buf + bs->rp, l, buf);
+ if (w == 0) panic("no feed");
+ bs->fl += w;
+ bs->rl -= w;
+ bs->rp = (bs->rp + w) % bs->bufsize;
+ /* Accumulate the total bytes of the moved samples. */
+ wacc += w;
+ }
+
+ return wacc;
+}
+
/* read interrupt routine. Must be called with interrupts blocked. */
static void
chn_rdintr(pcm_channel *c)
@@ -383,7 +521,18 @@
b->dl, b->rp, b->rl, b->fp, b->fl));
/* Restart if have enough free space to absorb overruns */
if (c->flags & CHN_F_MAPPED) start = c->flags & CHN_F_TRIGGERED;
- else start = (b->fl > 0x200 && !(c->flags & CHN_F_ABORTING));
+ else {
+ /*
+ * Suck up the DMA buffer. This may result in making new
+ * captured data in the secondary buffer, thus we can wake
+ * up the top half if feed occurs.
+ */
+ if (chn_rdfeed(c) > 0) {
+ chn_dmawakeup(c);
+ while (chn_rdfeed(c) > 0);
+ }
+ start = (b->fl > 0x200 && !(c->flags & CHN_F_ABORTING));
+ }
if (start) {
int l = min(b->fl - 0x100, c->blocksize);
if (c->flags & CHN_F_MAPPED) l = c->blocksize;
@@ -431,7 +580,7 @@
int
chn_read(pcm_channel *c, struct uio *buf)
{
- int w, l, timeout, limit, ret = 0;
+ int ret = 0, timeout, limit;
long s;
snd_dbuf *b = &c->buffer;
@@ -441,33 +590,32 @@
return (EBUSY);
}
- if (!b->rl & !b->dl) chn_stintr(c);
+ s = spltty();
c->flags |= CHN_F_READING;
limit = buf->uio_resid - c->blocksize;
if (limit < 0) limit = 0;
- while (buf->uio_resid > limit) {
- s = spltty();
- chn_dmaupdate(c);
- splx(s);
- if (b->rl < DMA_ALIGN_THRESHOLD) {
- if (c->flags & CHN_F_NBIO) break;
- timeout = (buf->uio_resid - limit >= b->dl)? hz : 1;
- ret = tsleep(b, PRIBIO | PCATCH, "pcmrd", timeout);
+ /* Start capturing if not yet. */
+ if (!b->rl & !b->dl) chn_rdintr(c);
+ /* Suck up the DMA and secondary buffers. */
+ while (chn_rdfeed(c) > 0 || chn_rdfeed2nd(c, buf) > 0);
+ if (!(c->flags & CHN_F_NBIO)) {
+ /* Wait until all samples are captured. */
+ while (buf->uio_resid > 0) {
+ splx(s);
+ /* Wait for new pcm samples. */
+ timeout = (buf->uio_resid - limit >= b->dl)? hz / 20 : 1;
+ ret = tsleep(b, PRIBIO | PCATCH, "pcmrd", timeout);
+ s = spltty();
if (ret == EINTR) chn_abort(c);
if (ret == EINTR || ret == ERESTART) break;
- ret = 0;
- continue;
+ /* Start capturing if necessary. */
+ if (!b->rl & !b->dl) chn_rdintr(c);
+ /* Suck up the DMA and secondary buffers. */
+ while (chn_rdfeed(c) > 0 || chn_rdfeed2nd(c, buf) > 0);
}
- /* ensure we always have a whole number of samples */
- l = min(b->rl, b->bufsize - b->rp) & DMA_ALIGN_MASK;
- w = c->feeder->feed(c->feeder, c, b->buf + b->rp, l, buf);
- s = spltty();
- b->rl -= w;
- b->fl += w;
- b->rp = (b->rp + w) % b->bufsize;
- splx(s);
}
c->flags &= ~CHN_F_READING;
+ splx(s);
return ret;
}
@@ -534,6 +682,7 @@
chn_resetbuf(pcm_channel *c)
{
snd_dbuf *b = &c->buffer;
+ snd_dbuf *bs = &c->buffer2nd;
c->smegcnt = 0;
c->buffer.sample_size = 1;
@@ -547,6 +696,9 @@
b->prev_int_count = b->int_count = 0;
b->first_poll = 1;
b->underflow=0;
+ bs->rp = bs->fp = 0;
+ bs->dl = bs->rl = 0;
+ bs->fl = bs->bufsize;
}
void
@@ -631,6 +783,7 @@
long s;
int missing = 0;
snd_dbuf *b = &c->buffer;
+ snd_dbuf *bs = &c->buffer2nd;
s = spltty();
if (b->dl) {
@@ -639,7 +792,7 @@
chn_trigger(c, PCMTRIG_ABORT);
chn_dmadone(c);
}
- missing = b->rl;
+ missing = b->rl + bs->rl;
splx(s);
return missing;
}
@@ -708,11 +861,18 @@
int
chn_init(pcm_channel *c, void *devinfo, int dir)
{
+ snd_dbuf *bs = &c->buffer2nd;
+
c->flags = 0;
c->feeder = &feeder_root;
c->buffer.chan = -1;
c->devinfo = c->init(devinfo, &c->buffer, c, dir);
chn_setdir(c, dir);
+ bs->bufsize = CHN_2NDBUFBLKSIZE * CHN_2NDBUFBLKNUM;
+ bs->buf = malloc(bs->bufsize, M_DEVBUF, M_NOWAIT);
+ bzero(bs->buf, bs->bufsize);
+ bs->rl = bs->rp = bs->fp = 0;
+ bs->fl = bs->bufsize;
return 0;
}
Index: channel.h
===================================================================
RCS file: /home/ncvs/src/sys/dev/sound/pcm/channel.h,v
retrieving revision 1.3
diff -u -r1.3 channel.h
--- channel.h 1999/09/28 21:43:34 1.3
+++ channel.h 1999/12/12 03:46:41
@@ -79,3 +79,12 @@
#define CHN_F_RESET (CHN_F_BUSY)
+
+/*
+ * This should be large enough to hold all pcm data between
+ * tsleeps in chn_{read,write} at the highest sample rate.
+ * (which is usually 48kHz * 16bit * stereo = 192000 bytes/sec)
+ */
+#define CHN_2NDBUFBLKSIZE (12 * 1024)
+/* The total number of blocks per secondary buffer. */
+#define CHN_2NDBUFBLKNUM (3)
Index: datatypes.h
===================================================================
RCS file: /home/ncvs/src/sys/dev/sound/pcm/datatypes.h,v
retrieving revision 1.6
diff -u -r1.6 datatypes.h
--- datatypes.h 1999/12/12 02:18:57 1.6
+++ datatypes.h 1999/12/12 03:46:41
@@ -127,6 +127,7 @@
u_int8_t smegbuf[SMEGBUFSZ];
u_int32_t smegcnt;
void *devinfo;
+ snd_dbuf buffer2nd;
};
typedef void (pcm_swap_t)(void *data, int dir);
Index: dsp.c
===================================================================
RCS file: /home/ncvs/src/sys/dev/sound/pcm/dsp.c,v
retrieving revision 1.11
diff -u -r1.11 dsp.c
--- dsp.c 1999/12/12 02:18:57 1.11
+++ dsp.c 1999/12/12 03:46:41
@@ -325,7 +325,7 @@
#define THE_REAL_SNDCTL_DSP_GETBLKSIZE _IOWR('P', 4, int)
case THE_REAL_SNDCTL_DSP_GETBLKSIZE:
case SNDCTL_DSP_GETBLKSIZE:
- *arg_i = wrch? wrch->blocksize : 0; /* XXX rdch? */
+ *arg_i = CHN_2NDBUFBLKSIZE;
break ;
case SNDCTL_DSP_SETBLKSIZE:
--
Seigo Tanimura <tanimura@r.dl.itc.u-tokyo.ac.jp> <tanimura@freebsd.org>
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