[haiku-commits] r42777 - haiku/trunk/src/add-ons/accelerants/common
- From: kallisti5@xxxxxxxxxxx
- To: haiku-commits@xxxxxxxxxxxxx
- Date: Thu, 29 Sep 2011 17:03:50 +0200 (CEST)
Author: kallisti5
Date: 2011-09-29 17:03:49 +0200 (Thu, 29 Sep 2011)
New Revision: 42777
Changeset: https://dev.haiku-os.org/changeset/42777
Modified:
haiku/trunk/src/add-ons/accelerants/common/i2c.c
Log:
* reading through i2c specs, little comment cleanup
* add a few notes for future i2c bit-bangers
* cleanup of tracing
* no real functional change
Modified: haiku/trunk/src/add-ons/accelerants/common/i2c.c
===================================================================
--- haiku/trunk/src/add-ons/accelerants/common/i2c.c 2011-09-28 13:06:48 UTC
(rev 42776)
+++ haiku/trunk/src/add-ons/accelerants/common/i2c.c 2011-09-29 15:03:49 UTC
(rev 42777)
@@ -14,6 +14,7 @@
#include <OS.h>
#include <string.h>
+
//#define TRACE_I2C
#ifdef TRACE_I2C
#ifdef __cplusplus
@@ -26,7 +27,11 @@
#endif
-//! Timining for 100kHz bus (fractional parts are rounded up)
+/*!
+ I2c timings, rounded up (Phillips 1995 i2c bus specification, p20)
+*/
+
+//! Timing for standard mode i2c (100kHz max)
const static i2c_timing kTiming100k = {
.buf = 5,
.hd_sta = 4,
@@ -38,8 +43,8 @@
.r = 2,
.f = 2,
.su_sto = 4,
-
- // as these are unspecified, we use half a clock cycle as a safe guess
+
+ // these are unspecified, use half a clock cycle as a safe guess
.start_timeout = 5,
.byte_timeout = 5,
.bit_timeout = 5,
@@ -47,8 +52,7 @@
.ack_timeout = 5
};
-// timing for 400 kHz bus
-// (argh! heavy up-rounding here)
+//! Timing for fast mode i2c (400kHz max)
const static i2c_timing kTiming400k = {
.buf = 2,
.hd_sta = 1,
@@ -60,8 +64,8 @@
.r = 1,
.f = 1,
.su_sto = 1,
-
- // see kTiming100k
+
+ // these are unspecified, use half a clock cycle as a safe guess
.start_timeout = 2,
.byte_timeout = 2,
.bit_timeout = 2,
@@ -71,7 +75,7 @@
/*!
- There's no spin in user space, but we need it to wait a couple
+ There's no spin in user space, but we need it to wait a couple
of microseconds only
(in this case, snooze has much too much overhead)
*/
@@ -121,7 +125,7 @@
status = wait_for_clk(bus, bus->timing.start_timeout);
if (status != B_OK) {
- TRACE("send_start_condition(): Timeout sending start
condition\n");
+ TRACE("%s: Timeout sending start condition\n", __func__);
return status;
}
@@ -149,7 +153,7 @@
// to make the slave release bus control
status = wait_for_clk(bus, bus->timing.ack_timeout);
if (status != B_OK) {
- TRACE("send_stop_condition(): Timeout sending stop
condition\n");
+ TRACE("%s: Timeout sending stop condition\n", __func__);
return status;
}
@@ -175,7 +179,7 @@
status = wait_for_clk(bus, timeout);
if (status != B_OK) {
- TRACE("send_bit(): Timeout when sending next bit\n");
+ TRACE("%s: Timeout when sending next bit\n", __func__);
return status;
}
@@ -201,7 +205,7 @@
status = wait_for_clk(bus, bus->timing.ack_start_timeout);
if (status != B_OK) {
- TRACE("send_acknowledge(): Timeout when sending acknowledge\n");
+ TRACE("%s: Timeout when sending acknowledge\n", __func__);
return status;
}
@@ -218,8 +222,8 @@
break;
if (system_time() - startTime > bus->timing.ack_timeout) {
- TRACE("send_acknowledge(): Slave didn't acknowledge
byte within ack_timeout: %ld\n",
- bus->timing.ack_timeout);
+ TRACE("%s: slave didn't acknowledge byte within
ack_timeout: %ld\n",
+ __func__, bus->timing.ack_timeout);
return B_TIMEOUT;
}
@@ -228,7 +232,7 @@
TRACE("send_acknowledge(): Success!\n");
- // make sure we've waited at least t_high
+ // make sure we've waited at least t_high
spin(bus->timing.high);
bus->set_signals(bus->cookie, 0, 1);
@@ -244,10 +248,10 @@
{
int i;
- //TRACE("send_byte(byte = %x)\n", byte);
+ //TRACE("%s: (byte = %x)\n", __func__, byte);
for (i = 7; i >= 0; --i) {
- status_t status = send_bit(bus, byte >> i,
+ status_t status = send_bit(bus, byte >> i,
i == 7 ? bus->timing.byte_timeout :
bus->timing.bit_timeout);
if (status != B_OK)
return status;
@@ -266,6 +270,7 @@
{
status_t status;
+ TRACE("%s: 0x%X\n", __func__, slaveAddress);
status = send_byte(bus, (slaveAddress & 0xfe) | !isWrite, true);
if (status != B_OK)
return status;
@@ -279,7 +284,7 @@
// - 0000 1xxx |-> reserved
// - 1111 1xxx |
// - 1111 0xxx - 10 bit address (second byte contains remaining 8 bits)
-
+
// the lsb is 0 for write and 1 for read (except for general call
address)
if ((slaveAddress & 0xff) != 0 && (slaveAddress & 0xf8) != 0xf0)
return B_OK;
@@ -302,7 +307,7 @@
// wait for slave to raise clock
status = wait_for_clk(bus, timeout);
if (status != B_OK) {
- TRACE("receive_bit(): Timeout waiting for bit sent by slave\n");
+ TRACE("%s: Timeout waiting for bit sent by slave\n", __func__);
return status;
}
@@ -319,7 +324,7 @@
// let it settle and leave it low for minimal time
// to make sure slave has finished bit transmission too
- *bit = data;
+ *bit = data;
return B_OK;
}
@@ -360,7 +365,7 @@
static status_t
send_bytes(const i2c_bus *bus, const uint8 *writeBuffer, ssize_t writeLength)
{
- TRACE("send_bytes(length = %ld)\n", writeLength);
+ TRACE("%s: (length = %ld)\n", __func__, writeLength);
for (; writeLength > 0; --writeLength, ++writeBuffer) {
status_t status = send_byte(bus, *writeBuffer, true);
@@ -376,7 +381,7 @@
static status_t
receive_bytes(const i2c_bus *bus, uint8 *readBuffer, ssize_t readLength)
{
- TRACE("receive_bytes(length = %ld)\n", readLength);
+ TRACE("%s: (length = %ld)\n", __func__, readLength);
for (; readLength > 0; --readLength, ++readBuffer) {
status_t status = receive_byte(bus, readBuffer, readLength > 1);
@@ -423,7 +428,7 @@
return send_stop_condition(bus);
err:
- TRACE("i2c_send_receive(): Cancelling transmission\n");
+ TRACE("%s: Cancelling transmission\n", __func__);
send_stop_condition(bus);
return status;
}
@@ -432,6 +437,7 @@
void
i2c_get100k_timing(i2c_timing *timing)
{
+ // AKA standard i2c mode
memcpy(timing, &kTiming100k, sizeof(i2c_timing));
}
@@ -439,5 +445,6 @@
void
i2c_get400k_timing(i2c_timing *timing)
{
+ // AKA fast i2c mode
memcpy(timing, &kTiming400k, sizeof(i2c_timing));
}
Other related posts:
- » [haiku-commits] r42777 - haiku/trunk/src/add-ons/accelerants/common - kallisti5
