The Apple SMC is implemented on a H8S/2117 chip. Communication with the chip

becomes much more reliably if we pay attention to the IBF and OBF flags.
This removes the need for excessive delays and retries, making operations
complete in microseconds instead of seconds.

This diff also removes flushing the read buffer after a read operations.  This
doesn't seem to be necessary, but we might need to put that back if the
length of a reply changes for some keys.

ok jung@, deraadt@

1 files changed, 41 insertions, 32 deletions

diff --git a/sys/dev/isa/asmc.c b/sys/dev/isa/asmc.c
index 6a53d2303e8..f04a31a6a83 100644
--- a/sys/dev/isa/asmc.c
+++ b/sys/dev/isa/asmc.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: asmc.c,v 1.21 2015/12/15 20:58:22 jung Exp $	*/
+/*	$OpenBSD: asmc.c,v 1.22 2015/12/22 19:04:42 kettenis Exp $	*/
 /*
  * Copyright (c) 2015 Joerg Jung <jung@openbsd.org>
  *
@@ -44,7 +44,11 @@
 #define ASMC_WRITE	0x11	/* SMC write command */
 #define ASMC_INFO	0x13	/* SMC info/type command */
 
-#define ASMC_RETRY	10
+#define ASMC_OBF	0x01	/* Output buffer full */
+#define ASMC_IBF	0x02	/* Input buffer full */
+#define ASMC_ACCEPT	0x04
+
+#define ASMC_RETRY	3
 #define ASMC_MAXLEN	32	/* SMC maximum data size len */
 #define ASMC_NOTFOUND	0x84	/* SMC status key not found */
 
@@ -385,11 +389,8 @@ asmc_kbdled(void *arg)
 	int r;
 
 	if ((r = asmc_try(sc, ASMC_WRITE, "LKSB", buf, 2)))
-#if 0 /* todo: write error, as no 0x04 wait status, but led is changed */
 		printf("%s: keyboard backlight failed (0x%x)\n",
 		    sc->sc_dev.dv_xname, r);
-#endif
-		;
 }
 
 int
@@ -436,44 +437,57 @@ asmc_status(struct asmc_softc *sc)
 }
 
 static int
-asmc_wait(struct asmc_softc *sc, uint8_t m)
+asmc_write(struct asmc_softc *sc, uint8_t off, uint8_t val)
 {
-	int us;
+	uint8_t str;
+	int i;
 
-	for (us = (2 << 4); us < (2 << 16); us *= 2) { /* wait up to 128 ms */
-		(!sc->sc_sensor_task) ? delay(us) :
-		    tsleep(&sc->sc_taskq, 0, "asmc",
-		        (us * hz + 999999) / 1000000 + 1);
-		if (bus_space_read_1(sc->sc_iot, sc->sc_ioh, ASMC_COMMAND) & m)
-			return 1;
+	for (i = 500; i > 0; i--) {
+		str = bus_space_read_1(sc->sc_iot, sc->sc_ioh, ASMC_COMMAND);
+		if ((str & ASMC_IBF) == 0)
+			break;
+		delay(10);
 	}
-	return 0;
-}
+	if (i == 0)
+		return ETIMEDOUT;
 
-static int
-asmc_write(struct asmc_softc *sc, uint8_t off, uint8_t val)
-{
 	bus_space_write_1(sc->sc_iot, sc->sc_ioh, off, val);
-	if (asmc_wait(sc, 0x04)) /* write accepted? */
-		return 0;
-	return 1;
+
+	for (i = 500; i > 0; i--) {
+		str = bus_space_read_1(sc->sc_iot, sc->sc_ioh, ASMC_COMMAND);
+		if (str & ASMC_ACCEPT)
+			break;
+		delay(10);
+	}
+	if (i == 0)
+		return ETIMEDOUT;
+
+	return 0;
 }
 
 static int
 asmc_read(struct asmc_softc *sc, uint8_t off, uint8_t *buf)
 {
-	if (asmc_wait(sc, 0x01)) { /* ready for read? */
-		*buf = bus_space_read_1(sc->sc_iot, sc->sc_ioh, off);
-		return 0;
+	uint8_t str;
+	int i;
+
+	for (i = 500; i > 0; i--) {
+		str = bus_space_read_1(sc->sc_iot, sc->sc_ioh, ASMC_COMMAND);
+		if (str & ASMC_OBF)
+			break;
+		delay(10);
 	}
-	return 1;
+	if (i == 0)
+		return ETIMEDOUT;
+
+	*buf = bus_space_read_1(sc->sc_iot, sc->sc_ioh, off);
+	return 0;
 }
 
 static int
 asmc_command(struct asmc_softc *sc, int cmd, const char *key, uint8_t *buf,
     uint8_t len)
 {
-	uint8_t n;
 	int i;
 
 	if (len > ASMC_MAXLEN)
@@ -489,9 +503,6 @@ asmc_command(struct asmc_softc *sc, int cmd, const char *key, uint8_t *buf,
 		for (i = 0; i < len; i++)
 			if (asmc_read(sc, ASMC_DATA, &buf[i]))
 				return 1;
-		for (i = 0; i < ASMC_MAXLEN; i++) /* sanity flush */
-			if (asmc_read(sc, ASMC_DATA, &n))
-				break;
 	} else if (cmd == ASMC_WRITE) {
 		for (i = 0; i < len; i++)
 			if (asmc_write(sc, ASMC_DATA, buf[i]))
@@ -515,9 +526,7 @@ asmc_try(struct asmc_softc *sc, int cmd, const char *key, uint8_t *buf,
 	if (r && (s = asmc_status(sc)))
 		r = s;
 	rw_exit_write(&sc->sc_lock);
-	if (sc->sc_sensor_task) /* give kbdled a chance to grab the lock */
-		tsleep(&sc->sc_taskq, 0, "asmc",
-		    (1 * hz + 999999) / 1000000 + 1);
+
 	return r;
 }