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drivers/1wire/ds28e17.c: Optimize I2C write followed by read to same address.

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This commit is contained in:
Juha Niskanen 2018-12-11 07:09:03 -06:00 committed by Gregory Nutt
parent 39c51e668f
commit 583e80a9ce
2 changed files with 131 additions and 5 deletions
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5
drivers/1wire/1wire.c
View File

@ -206,6 +206,11 @@ static int onewire_pm_prepare(FAR struct pm_callback_s *cb, int domain,
}
break;
default:
/* Should not get here */
break;
}
return OK;

131
drivers/1wire/ds28e17.c
View File

@ -375,7 +375,7 @@ static int ds_i2c_write(FAR struct ds_i2c_inst_s *inst, uint16_t i2c_addr,
FAR struct onewire_master_s *master = inst->master;
uint16_t crc;
int ret;
uint8_t buf[5];
uint8_t buf[3];
if (length <= 0)
{
@ -453,6 +453,105 @@ static int ds_i2c_write(FAR struct ds_i2c_inst_s *inst, uint16_t i2c_addr,
return length;
}
/****************************************************************************
* Name: ds_i2c_write_read
*
* Description:
* Write data to I2C slave and read from same address.
*
****************************************************************************/
static int ds_i2c_write_read(FAR struct ds_i2c_inst_s *inst, uint16_t i2c_addr,
FAR const uint8_t *wbuffer, ssize_t wlength,
FAR uint8_t *rbuffer, ssize_t rlength)
{
FAR struct onewire_master_s *master = inst->master;
uint16_t crc;
int ret;
uint8_t buf[3];
if (wlength <= 0 || rlength <= 0)
{
return -EINVAL;
}
if (wlength > DS_DATA_LIMIT)
{
i2cerr("ERROR: writing too many bytes!\n");
return -EINVAL;
}
if (rlength > DS_DATA_LIMIT)
{
i2cerr("ERROR: reading too many bytes!\n");
return -EINVAL;
}
/* Write command header. */
buf[0] = DS_WRITE_READ_DATA_WITH_STOP;
buf[1] = i2c_addr << 1;
buf[2] = wlength;
crc = onewire_crc16(buf, 3, 0);
ret = ONEWIRE_WRITE(master->dev, buf, 3);
if (ret < 0)
{
return ret;
}
/* Write payload I2C data to DS28E17. */
crc = onewire_crc16(wbuffer, wlength, crc);
ret = ONEWIRE_WRITE(master->dev, wbuffer, wlength);
if (ret < 0)
{
return ret;
}
/* Write read length and checksum. */
buf[0] = rlength;
crc = onewire_crc16(buf, 1, crc);
buf[1] = ~(crc & 0xff);
buf[2] = ~((crc >> 8) & 0xff);
ret = ONEWIRE_WRITE(master->dev, buf, 3);
if (ret < 0)
{
return ret;
}
/* Wait busy indication to vanish. */
ret = ds_busywait(inst, wlength + 1 + rlength + 1);
if (ret < 0)
{
return ret;
}
/* Read status from DS28E17. */
ret = ONEWIRE_READ(master->dev, buf, 2);
if (ret < 0)
{
return ret;
}
/* Check error conditions. */
ret = ds_error(buf);
if (ret < 0)
{
return ret;
}
/* Read received I2C data from DS28E17. */
return ONEWIRE_READ(master->dev, rbuffer, rlength);
}
static int ds_i2c_setfrequency(FAR struct ds_i2c_inst_s *inst, uint32_t frequency)
{
FAR struct onewire_master_s *master = inst->master;
@ -542,11 +641,30 @@ static int ds_i2c_process(FAR struct i2c_master_s *i2cdev,
while (i < count)
{
/* TODO: we could use DS_WRITE_READ_DATA_WITH_STOP to optimize the
* common case of write followed by read to a same address.
/* First we try to use DS_WRITE_READ_DATA_WITH_STOP to optimize
* the common case of write followed by read to a same address.
*/
if (msgs[i].flags & I2C_M_READ)
if (i < count - 1 && msgs[i].addr == msgs[i+1].addr &&
(msgs[i].flags & I2C_M_READ) == 0 &&
(msgs[i+1].flags & I2C_M_READ))
{
/* Write-read combined transfer. */
ret = ds_i2c_write_read(inst, msgs[i].addr,
msgs[i].buffer, msgs[i].length,
msgs[i+1].buffer, msgs[i+1].length);
if (ret < 0)
{
i = ret;
goto errout;
}
/* We processed two messages here. */
i += 2;
}
else if (msgs[i].flags & I2C_M_READ)
{
/* Read transfer. */
@ -556,6 +674,8 @@ static int ds_i2c_process(FAR struct i2c_master_s *i2cdev,
i = ret;
goto errout;
}
i++;
}
else
{
@ -568,11 +688,12 @@ static int ds_i2c_process(FAR struct i2c_master_s *i2cdev,
i = ret;
goto errout;
}
i++;
}
/* Any more messages to process? */
i++;
if (i < count)
{
/* Yes. Resume to same DS28E17. */