3 files changed, 14 insertions, 7 deletions

diff --git a/sys/dev/iicbus/twsi/a10_twsi.c b/sys/dev/iicbus/twsi/a10_twsi.c
index e70e33fbe2290..17f551f27234e 100644
--- a/sys/dev/iicbus/twsi/a10_twsi.c
+++ b/sys/dev/iicbus/twsi/a10_twsi.c
@@ -122,6 +122,10 @@ a10_twsi_attach(device_t dev)
 	sc->reg_soft_reset = TWI_SRST;
 
 	sc->need_ack = true;
+
+	if (ofw_bus_is_compatible(dev, "allwinner,sun6i-a31-i2c") ||
+	    ofw_bus_is_compatible(dev, "allwinner,sun6i-a83t-i2c"))
+		sc->iflag_w1c = true;
 	return (twsi_attach(dev));
 }
 
diff --git a/sys/dev/iicbus/twsi/twsi.c b/sys/dev/iicbus/twsi/twsi.c
index 9d1a17f43103c..a606c2aefd361 100644
--- a/sys/dev/iicbus/twsi/twsi.c
+++ b/sys/dev/iicbus/twsi/twsi.c
@@ -147,7 +147,11 @@ twsi_clear_iflg(struct twsi_softc *sc)
 {
 
 	DELAY(1000);
-	twsi_control_clear(sc, TWSI_CONTROL_IFLG);
+	/* There are two ways of clearing IFLAG. */
+	if (sc->iflag_w1c)
+		twsi_control_set(sc, TWSI_CONTROL_IFLG);
+	else
+		twsi_control_clear(sc, TWSI_CONTROL_IFLG);
 	DELAY(1000);
 }
 
@@ -667,13 +671,11 @@ twsi_intr(void *arg)
 	}
 	debugf(sc->dev, "Refresh reg_control\n");
 
-	/* 
-	 * Fix silicon bug on > Allwinner A20 by doing a read and writing
-	 * again to the control register
+	/*
+	 * Newer Allwinner chips clear IFLG after writing 1 to it.
 	 */
-	status = TWSI_READ(sc, sc->reg_status);
-	TWSI_WRITE(sc, sc->reg_control,
-	  sc->control_val | TWSI_CONTROL_IFLG);
+	TWSI_WRITE(sc, sc->reg_control, sc->control_val |
+	    (sc->iflag_w1c ? TWSI_CONTROL_IFLG : 0));
 
 	debugf(sc->dev, "Done with interrupts\n\n");
 	if (transfer_done == 1) {
diff --git a/sys/dev/iicbus/twsi/twsi.h b/sys/dev/iicbus/twsi/twsi.h
index a0c4958b47de7..631486fb3f0c3 100644
--- a/sys/dev/iicbus/twsi/twsi.h
+++ b/sys/dev/iicbus/twsi/twsi.h
@@ -66,6 +66,7 @@ struct twsi_softc {
 	int			error;
 	uint32_t		control_val;
 	bool			need_ack;
+	bool			iflag_w1c;
 
 	bus_size_t	reg_data;
 	bus_size_t	reg_slave_addr;