[src/trunk]: src/sys/dev/pad Rework of previous.

[nat <nat%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/afc1632441c3
branches:  trunk
changeset: 353888:afc1632441c3
user:      nat <nat%NetBSD.org@localhost>
date:      Sat May 27 10:02:26 2017 +0000

description:
Rework of previous.
Math for BYTESTOSLEEP and TIMENEXTREAD is now correct.

diffstat:

 sys/dev/pad/pad.c    |  37 ++++++++++++++++++++++++++-----------
 sys/dev/pad/padvar.h |   4 +++-
 2 files changed, 29 insertions(+), 12 deletions(-)

diffs (102 lines):

diff -r 9abc8d200985 -r afc1632441c3 sys/dev/pad/pad.c
--- a/sys/dev/pad/pad.c Sat May 27 06:32:12 2017 +0000
+++ b/sys/dev/pad/pad.c Sat May 27 10:02:26 2017 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: pad.c,v 1.28 2017/02/23 23:13:27 nat Exp $ */
+/* $NetBSD: pad.c,v 1.29 2017/05/27 10:02:26 nat Exp $ */
 
 /*-
  * Copyright (c) 2007 Jared D. McNeill <jmcneill%invisible.ca@localhost>
@@ -27,7 +27,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: pad.c,v 1.28 2017/02/23 23:13:27 nat Exp $");
+__KERNEL_RCSID(0, "$NetBSD: pad.c,v 1.29 2017/05/27 10:02:26 nat Exp $");
 
 #include <sys/types.h>
 #include <sys/param.h>
@@ -321,6 +321,8 @@
        }
        
        getmicrotime(&sc->sc_last);
+       sc->sc_bytes_count = 0;
+       sc->sc_remainder = 0;
 
        return 0;
 }
@@ -340,8 +342,9 @@
        return 0;
 }
 
-#define PAD_BYTES_PER_SEC (44100 * sizeof(int16_t) * 2)
-#define TIMENEXTREAD   (PAD_BLKSIZE * 1000 / PAD_BYTES_PER_SEC)
+#define PAD_BYTES_PER_SEC   (44100 * sizeof(int16_t) * 2)
+#define TIMENEXTREAD       (PAD_BLKSIZE * 1000000 / PAD_BYTES_PER_SEC)
+#define BYTESTOSLEEP       (PAD_BLKSIZE)
 
 int
 pad_read(dev_t dev, struct uio *uio, int flags)
@@ -369,18 +372,28 @@
                nowusec = (now.tv_sec * 1000000) + now.tv_usec;
                lastusec = (sc->sc_last.tv_sec * 1000000) +
                     sc->sc_last.tv_usec;
-               if (lastusec + TIMENEXTREAD > nowusec) {
-                       wait_ticks = (hz * ((lastusec + TIMENEXTREAD) -
-                            nowusec)) / 1000000;
+               if (lastusec + TIMENEXTREAD > nowusec &&
+                    sc->sc_bytes_count >= BYTESTOSLEEP) {
+                       sc->sc_remainder +=
+                           ((lastusec + TIMENEXTREAD) - nowusec);
+                       
+                       wait_ticks = (hz * sc->sc_remainder) / 1000000;
                        if (wait_ticks > 0) {
+                               sc->sc_remainder -= wait_ticks * 1000000 / hz;
                                kpause("padwait", TRUE, wait_ticks,
                                    &sc->sc_lock);
                        }
+
+                       sc->sc_bytes_count -= BYTESTOSLEEP;
+                       getmicrotime(&sc->sc_last);
+               } else if (sc->sc_bytes_count >= BYTESTOSLEEP) {
+                       sc->sc_bytes_count -= BYTESTOSLEEP;
+                       getmicrotime(&sc->sc_last);
+               } else if (lastusec + TIMENEXTREAD <= nowusec) {
+                       getmicrotime(&sc->sc_last);
+                       sc->sc_remainder = 0;
                }
-               sc->sc_last.tv_sec =
-                       (lastusec + TIMENEXTREAD) / 1000000;
-               sc->sc_last.tv_usec =
-                       (lastusec + TIMENEXTREAD) % 1000000;
+
                err = pad_get_block(sc, &pb, min(uio->uio_resid, PAD_BLKSIZE));
                if (!err) {
                        mutex_exit(&sc->sc_lock);
@@ -422,6 +435,8 @@
                return EIO;
 
        getmicrotime(&sc->sc_last);
+       sc->sc_remainder = 0;
+
        return 0;
 }
 
diff -r 9abc8d200985 -r afc1632441c3 sys/dev/pad/padvar.h
--- a/sys/dev/pad/padvar.h      Sat May 27 06:32:12 2017 +0000
+++ b/sys/dev/pad/padvar.h      Sat May 27 10:02:26 2017 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: padvar.h,v 1.7 2017/02/23 23:13:27 nat Exp $ */
+/* $NetBSD: padvar.h,v 1.8 2017/05/27 10:02:26 nat Exp $ */
 
 /*-
  * Copyright (c) 2007 Jared D. McNeill <jmcneill%invisible.ca@localhost>
@@ -52,6 +52,8 @@
 
        uint8_t         sc_swvol;
        struct timeval  sc_last;
+       int             sc_bytes_count;
+       uint32_t        sc_remainder;
 } pad_softc_t;
 
 #endif /* !_SYS_DEV_PAD_PADVAR_H */