Author: ian
Date: Mon Jul 15 21:40:58 2019
New Revision: 350015
URL: https://svnweb.freebsd.org/changeset/base/350015
Log:
Fix nxprtc(4) on systems that support i2c repeat-start correctly.
An obscure footnote in the datasheets for the PCx2127, PCx2129, and
PCF8523 rtc chips states that the chips do not support i2c repeat-start
operations. When the driver was originally written and tested, the i2c
bus on that system also didn't support repeat-start and just quietly
turned repeat-start operations into a stop-then-start, making it appear
that the nxprtc driver was working properly.
The repeat-start situation only comes up on reads, so instead of using
the standard iicdev_readfrom(), use a local nxprtc_readfrom(), which is
just a cut-and-pasted copy of iicdev_readfrom(), modified to send two
separate start-data-stop sequences instead of using repeat-start.
Modified:
head/sys/dev/iicbus/nxprtc.c
Modified: head/sys/dev/iicbus/nxprtc.c
==============================================================================
--- head/sys/dev/iicbus/nxprtc.c Mon Jul 15 21:26:55 2019
(r350014)
+++ head/sys/dev/iicbus/nxprtc.c Mon Jul 15 21:40:58 2019
(r350015)
@@ -236,10 +236,43 @@ static nxprtc_compat_data compat_data[] = {
};
static int
+nxprtc_readfrom(device_t slavedev, uint8_t regaddr, void *buffer,
+ uint16_t buflen, int waithow)
+{
+ struct iic_msg msg;
+ int err;
+ uint8_t slaveaddr;
+
+ /*
+ * Two transfers back to back with a stop and start between them; first
we
+ * write the address-within-device, then we read from the device. This
+ * is used instead of the standard iicdev_readfrom() because some of the
+ * chips we service don't support i2c repeat-start operations (grrrrr)
+ * so we do two completely separate transfers with a full stop between.
+ */
+ slaveaddr = iicbus_get_addr(slavedev);
+
+ msg.slave = slaveaddr;
+ msg.flags = IIC_M_WR;
+ msg.len = 1;
+ msg.buf = ®addr;
+
+ if ((err = iicbus_transfer_excl(slavedev, &msg, 1, waithow)) != 0)
+ return (err);
+
+ msg.slave = slaveaddr;
+ msg.flags = IIC_M_RD;
+ msg.len = buflen;
+ msg.buf = buffer;
+
+ return (iicbus_transfer_excl(slavedev, &msg, 1, waithow));
+}
+
+static int
read_reg(struct nxprtc_softc *sc, uint8_t reg, uint8_t *val)
{
- return (iicdev_readfrom(sc->dev, reg, val, sizeof(*val), WAITFLAGS));
+ return (nxprtc_readfrom(sc->dev, reg, val, sizeof(*val), WAITFLAGS));
}
static int
@@ -272,7 +305,7 @@ read_timeregs(struct nxprtc_softc *sc, struct time_reg
if (tmr1 != tmr2)
continue;
}
- if ((err = iicdev_readfrom(sc->dev, sc->secaddr, tregs,
+ if ((err = nxprtc_readfrom(sc->dev, sc->secaddr, tregs,
sizeof(*tregs), WAITFLAGS)) != 0)
break;
} while (sc->use_timer && tregs->sec != sec);
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