Remove unnecessary delays. There is no reason to wait after each and every

read or write to aregister.  There is also no reason to wait after
transmitting a STOP since the controller will wait until the bus is free
when transmitting the next START.  Based on a diff by Stephen Graf.

Also remove the interrupt code; it doesn't work on the newer variants of
the device.  The functionality will be put back in a future commit.

ok patrick@

diff --git a/sys/dev/fdt/sxitwi.c b/sys/dev/fdt/sxitwi.c
index b409942..98eae99 100644 (file)
--- a/sys/dev/fdt/sxitwi.c
+++ b/sys/dev/fdt/sxitwi.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sxitwi.c,v 1.5 2017/12/30 19:04:00 kettenis Exp $ */
+/* $OpenBSD: sxitwi.c,v 1.6 2018/01/05 12:46:13 kettenis Exp $ */
 /*     $NetBSD: gttwsi_core.c,v 1.2 2014/11/23 13:37:27 jmcneill Exp $ */
 /*
  * Copyright (c) 2008 Eiji Kawauchi.
@@ -128,12 +128,6 @@
 
 #define        SOFTRESET_VAL           0               /* reset value */
 
-#define        TWSI_RETRY_COUNT        1000            /* retry loop count */
-#define        TWSI_RETRY_DELAY        1               /* retry delay */
-#define        TWSI_STAT_DELAY         1               /* poll status delay */
-#define        TWSI_READ_DELAY         2               /* read delay */
-#define        TWSI_WRITE_DELAY        2               /* write delay */
-
 struct sxitwi_softc {
        struct device            sc_dev;
        bus_space_tag_t          sc_iot;
@@ -291,21 +285,13 @@ sxitwi_bus_scan(struct device *self, struct i2cbus_attach_args *iba, void *arg)
 u_int
 sxitwi_read_4(struct sxitwi_softc *sc, u_int reg)
 {
-       u_int val = bus_space_read_4(sc->sc_iot, sc->sc_ioh, reg);
-
-       delay(TWSI_READ_DELAY);
-
-       return val;
+       return bus_space_read_4(sc->sc_iot, sc->sc_ioh, reg);
 }
 
 void
 sxitwi_write_4(struct sxitwi_softc *sc, u_int reg, u_int val)
 {
        bus_space_write_4(sc->sc_iot, sc->sc_ioh, reg, val);
-
-       delay(TWSI_WRITE_DELAY);
-
-       return;
 }
 
 int
@@ -317,7 +303,6 @@ sxitwi_intr(void *arg)
        val = sxitwi_read_4(sc, TWSI_CONTROL);
        if (val & CONTROL_IFLG) {
                sxitwi_write_4(sc, TWSI_CONTROL, val & ~CONTROL_INTEN);
-               wakeup(&sc->sc_dev);
                return 1;
        }
        return 0;
@@ -364,19 +349,15 @@ int
 sxitwi_send_stop(void *v, int flags)
 {
        struct sxitwi_softc *sc = v;
-       int retry = TWSI_RETRY_COUNT;
 
        sc->sc_started = 0;
 
-       /* Interrupt is not generated for STAT_NRS. */
+       /*
+        * No need to wait; the controller doesn't transmit the next
+        * START condition until the bus is free.
+        */
        sxitwi_write_4(sc, TWSI_CONTROL, CONTROL_STOP | sc->sc_twsien_iflg);
-       while (--retry > 0) {
-               if (sxitwi_read_4(sc, TWSI_STATUS) == STAT_NRS)
-                       return 0;
-               delay(TWSI_STAT_DELAY);
-       }
-
-       return -1;
+       return 0;
 }
 
 int
@@ -458,30 +439,21 @@ int
 sxitwi_wait(struct sxitwi_softc *sc, u_int control, u_int expect, int flags)
 {
        u_int status;
-       int timo, error = 0;
+       int timo;
 
-       delay(5);
-       if (!(flags & I2C_F_POLL))
-               control |= CONTROL_INTEN;
        sxitwi_write_4(sc, TWSI_CONTROL, control | sc->sc_twsien_iflg);
 
-       timo = 0;
-       do {
+       for (timo = 10000; timo > 0; timo--) {
                control = sxitwi_read_4(sc, TWSI_CONTROL);
                if (control & CONTROL_IFLG)
                        break;
-               if (flags & I2C_F_POLL)
-                       delay(TWSI_RETRY_DELAY);
-               else {
-                       error = tsleep(&sc->sc_dev, PWAIT, "sxitwi", 100);
-                       if (error)
-                               return error;
-               }
-       } while (++timo < 1000000);
+               delay(1);
+       }
+       if (timo == 0)
+               return ETIMEDOUT;
 
        status = sxitwi_read_4(sc, TWSI_STATUS);
        if (status != expect)
                return EIO;
-
-       return error;
+       return 0;
 }