svn commit: r354940 - stable/12/sys/dev/iicbus
Andriy Gapon
avg at FreeBSD.org
Thu Nov 21 07:48:04 UTC 2019
Author: avg
Date: Thu Nov 21 07:48:03 2019
New Revision: 354940
URL: https://svnweb.freebsd.org/changeset/base/354940
Log:
MFC r354212: iicbb: allow longer SCL low timeout and other improvements
First, SCL low timeout is set to 25 milliseconds by default as opposed
to 1 millisecond before. The new value is based on the SMBus
specification. The timeout can be changed on a per bus basis using
dev.iicbb.N.scl_low_timeout sysctl.
The driver uses DELAY to wait for high SCL up to 1 millisecond, then it
switches to pause_sbt(SBT_1MS) for the rest of the timeout.
While here I made a number of other changes. 'udelay' that's used for
timing clock and data signals is now calculated based on the requested
bus frequency (dev.iicbus.N.frequency) instead of being hardcoded to 10
microseconds. The calculations are done in such a fashion that the
default bus frequency of 100000 is converted to udelay of 10 us. This
is for backward compatibility. The actual frequency will be less than a
quarter (I think) of the requested frequency.
Also, I added detection of stuck low SCL in a few places. Previously,
the code would just carry on after the SCL low timeout and that might
potentially lead to misinterpreted bits.
Finally, I fixed several style issues near the code that I changed.
Many more are still remaining.
Modified:
stable/12/sys/dev/iicbus/iicbb.c
Directory Properties:
stable/12/ (props changed)
Modified: stable/12/sys/dev/iicbus/iicbb.c
==============================================================================
--- stable/12/sys/dev/iicbus/iicbb.c Thu Nov 21 07:39:33 2019 (r354939)
+++ stable/12/sys/dev/iicbus/iicbb.c Thu Nov 21 07:48:03 2019 (r354940)
@@ -52,6 +52,7 @@ __FBSDID("$FreeBSD$");
#include <sys/systm.h>
#include <sys/module.h>
#include <sys/bus.h>
+#include <sys/sysctl.h>
#include <sys/uio.h>
#ifdef FDT
@@ -68,9 +69,13 @@ __FBSDID("$FreeBSD$");
#include "iicbus_if.h"
#include "iicbb_if.h"
+/* Based on the SMBus specification. */
+#define DEFAULT_SCL_LOW_TIMEOUT (25 * 1000)
+
struct iicbb_softc {
device_t iicbus;
- int udelay; /* signal toggle delay in usec */
+ u_int udelay; /* signal toggle delay in usec */
+ u_int scl_low_timeout;
};
static int iicbb_attach(device_t);
@@ -86,6 +91,7 @@ static int iicbb_write(device_t, const char *, int, in
static int iicbb_read(device_t, char *, int, int *, int, int);
static int iicbb_reset(device_t, u_char, u_char, u_char *);
static int iicbb_transfer(device_t dev, struct iic_msg *msgs, uint32_t nmsgs);
+static void iicbb_set_speed(struct iicbb_softc *sc, u_char);
#ifdef FDT
static phandle_t iicbb_get_node(device_t, device_t);
#endif
@@ -142,9 +148,19 @@ iicbb_attach(device_t dev)
sc->iicbus = device_add_child(dev, "iicbus", -1);
if (!sc->iicbus)
return (ENXIO);
- sc->udelay = 10; /* 10 uS default */
- bus_generic_attach(dev);
+ sc->scl_low_timeout = DEFAULT_SCL_LOW_TIMEOUT;
+
+ SYSCTL_ADD_UINT(device_get_sysctl_ctx(dev),
+ SYSCTL_CHILDREN(device_get_sysctl_tree(dev)), OID_AUTO,
+ "delay", CTLFLAG_RD, &sc->udelay,
+ 0, "Signal change delay controlled by bus frequency, microseconds");
+
+ SYSCTL_ADD_UINT(device_get_sysctl_ctx(dev),
+ SYSCTL_CHILDREN(device_get_sysctl_tree(dev)), OID_AUTO,
+ "scl_low_timeout", CTLFLAG_RWTUN, &sc->scl_low_timeout,
+ 0, "SCL low timeout, microseconds");
+ bus_generic_attach(dev);
return (0);
}
@@ -201,24 +217,17 @@ iicbb_print_child(device_t bus, device_t dev)
return (retval);
}
-#define I2C_SETSDA(sc,dev,val) do { \
- IICBB_SETSDA(device_get_parent(dev), val); \
+#define I2C_GETSDA(dev) (IICBB_GETSDA(device_get_parent(dev)))
+#define I2C_SETSDA(dev, x) (IICBB_SETSDA(device_get_parent(dev), x))
+#define I2C_GETSCL(dev) (IICBB_GETSCL(device_get_parent(dev)))
+#define I2C_SETSCL(dev, x) (IICBB_SETSCL(device_get_parent(dev), x))
+
+#define I2C_SET(sc, dev, ctrl, val) do { \
+ iicbb_setscl(dev, ctrl); \
+ I2C_SETSDA(dev, val); \
DELAY(sc->udelay); \
} while (0)
-#define I2C_SETSCL(dev,val) do { \
- iicbb_setscl(dev, val, 100); \
- } while (0)
-
-#define I2C_SET(sc,dev,ctrl,data) do { \
- I2C_SETSCL(dev, ctrl); \
- I2C_SETSDA(sc, dev, data); \
- } while (0)
-
-#define I2C_GETSDA(dev) (IICBB_GETSDA(device_get_parent(dev)))
-
-#define I2C_GETSCL(dev) (IICBB_GETSCL(device_get_parent(dev)))
-
static int i2c_debug = 0;
#define I2C_DEBUG(x) do { \
if (i2c_debug) (x); \
@@ -229,20 +238,37 @@ static int i2c_debug = 0;
} while (0)
static void
-iicbb_setscl(device_t dev, int val, int timeout)
+iicbb_setscl(device_t dev, int val)
{
struct iicbb_softc *sc = device_get_softc(dev);
- int k = 0;
+ sbintime_t now, end;
+ int fast_timeout;
- IICBB_SETSCL(device_get_parent(dev), val);
+ I2C_SETSCL(dev, val);
DELAY(sc->udelay);
- while (val && !I2C_GETSCL(dev) && k++ < timeout) {
- IICBB_SETSCL(device_get_parent(dev), val);
+ /* Pulling low cannot fail. */
+ if (!val)
+ return;
+
+ /* Use DELAY for up to 1 ms, then switch to pause. */
+ end = sbinuptime() + sc->scl_low_timeout * SBT_1US;
+ fast_timeout = MIN(sc->scl_low_timeout, 1000);
+ while (fast_timeout > 0) {
+ if (I2C_GETSCL(dev))
+ return;
+ I2C_SETSCL(dev, 1); /* redundant ? */
DELAY(sc->udelay);
+ fast_timeout -= sc->udelay;
}
- return;
+ while (!I2C_GETSCL(dev)) {
+ now = sbinuptime();
+ if (now >= end)
+ break;
+ pause_sbt("iicbb-scl-low", SBT_1MS, C_PREL(8), 0);
+ }
+
}
static void
@@ -290,6 +316,11 @@ iicbb_ack(device_t dev, int timeout)
I2C_SET(sc,dev,0,1);
I2C_SET(sc,dev,1,1);
+
+ /* SCL must be high now. */
+ if (!I2C_GETSCL(dev))
+ return (IIC_ETIMEOUT);
+
do {
noack = I2C_GETSDA(dev);
if (!noack)
@@ -301,14 +332,14 @@ iicbb_ack(device_t dev, int timeout)
I2C_SET(sc,dev,0,1);
I2C_DEBUG(printf("%c ",noack?'-':'+'));
- return (noack);
+ return (noack ? IIC_ENOACK : 0);
}
static void
iicbb_sendbyte(device_t dev, u_char data, int timeout)
{
int i;
-
+
for (i=7; i>=0; i--) {
if (data&(1<<i)) {
iicbb_one(dev, timeout);
@@ -341,7 +372,7 @@ iicbb_readbyte(device_t dev, int last, int timeout)
iicbb_zero(dev, timeout);
}
I2C_DEBUG(printf("r%02x%c ",(int)data,last?'-':'+'));
- return data;
+ return (data);
}
static int
@@ -353,6 +384,7 @@ iicbb_callback(device_t dev, int index, caddr_t data)
static int
iicbb_reset(device_t dev, u_char speed, u_char addr, u_char *oldaddr)
{
+ iicbb_set_speed(device_get_softc(dev), speed);
return (IICBB_RESET(device_get_parent(dev), speed, addr, oldaddr));
}
@@ -365,6 +397,11 @@ iicbb_start(device_t dev, u_char slave, int timeout)
I2C_DEBUG(printf("<"));
I2C_SET(sc,dev,1,1);
+
+ /* SCL must be high now. */
+ if (!I2C_GETSCL(dev))
+ return (IIC_ETIMEOUT);
+
I2C_SET(sc,dev,1,0);
I2C_SET(sc,dev,0,0);
@@ -372,14 +409,10 @@ iicbb_start(device_t dev, u_char slave, int timeout)
iicbb_sendbyte(dev, slave, timeout);
/* check for ack */
- if (iicbb_ack(dev, timeout)) {
- error = IIC_ENOACK;
- goto error;
- }
+ error = iicbb_ack(dev, timeout);
+ if (error == 0)
+ return (0);
- return(0);
-
-error:
iicbb_stop(dev);
return (error);
}
@@ -394,6 +427,10 @@ iicbb_stop(device_t dev)
I2C_SET(sc,dev,1,1);
I2C_DEBUG(printf(">"));
I2C_DEBUG(printf("\n"));
+
+ /* SCL must be high now. */
+ if (!I2C_GETSCL(dev))
+ return (IIC_ETIMEOUT);
return (0);
}
@@ -408,15 +445,13 @@ iicbb_write(device_t dev, const char *buf, int len, in
iicbb_sendbyte(dev,(u_char)*buf++, timeout);
/* check for ack */
- if (iicbb_ack(dev, timeout)) {
- error = IIC_ENOACK;
- goto error;
- }
- bytes ++;
- len --;
+ error = iicbb_ack(dev, timeout);
+ if (error != 0)
+ break;
+ bytes++;
+ len--;
}
-error:
*sent = bytes;
return (error);
}
@@ -452,6 +487,24 @@ iicbb_transfer(device_t dev, struct iic_msg *msgs, uin
IICBB_POST_XFER(device_get_parent(dev));
return (error);
+}
+
+static void
+iicbb_set_speed(struct iicbb_softc *sc, u_char speed)
+{
+ u_int busfreq, period;
+
+ /*
+ * NB: the resulting frequency will be a quarter (even less) of the
+ * configured bus frequency. This is for historic reasons. The default
+ * bus frequency is 100 kHz. And the historic default udelay is 10
+ * microseconds. The cycle of sending a bit takes four udelay-s plus
+ * SCL is kept low for extra two udelay-s. The actual I/O toggling also
+ * has an overhead.
+ */
+ busfreq = IICBUS_GET_FREQUENCY(sc->iicbus, speed);
+ period = 1000000 / busfreq; /* Hz -> uS */
+ sc->udelay = MAX(period, 1);
}
DRIVER_MODULE(iicbus, iicbb, iicbus_driver, iicbus_devclass, 0, 0);
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