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Tiva I2C: Don't try to ACK and STOP on the same byte. Improve logic that suppresses STOP on a repeated start

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This commit is contained in:
Gregory Nutt 2014-12-12 12:13:31 -06:00
parent 54c8d5c6e4
commit c653ff5ce4
1 changed files with 47 additions and 8 deletions
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55
arch/arm/src/tiva/tiva_i2c.c
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@ -1044,27 +1044,65 @@ static void tiva_i2c_startxfr(struct tiva_i2c_priv_s *priv)
static void tiva_i2c_nextxfr(struct tiva_i2c_priv_s *priv, uint32_t cmd)
{
/* Set up the basic command. The STOP bit should be set on the last transfer
* UNLESS this there is a repeated start.
/* Set up the basic command. The STOP bit should be set on the last byte transfer.
*
* - CASE 1: If this is the last message in the sequence, then the stop bit should
* always be set.
* - CASE 2.1.1: The next message may be another read or write of the SAME
* direction (read or write) and to the SAME address WITHOUT repeated start, in
* which case this is really just a continuation of the message. No STOP is
* needed.
* - CASE 2.x.2: The next message may be to the SAME address WITH repeated start.
* Because the repeated start, a direction change is possible. This is still
* a continuation of the same message sequence and so no STOP is needed.
* - CASE 2.2.x: The next message may be a DIFFERENT address WITHOUT repeated
* start. This would be an error; The STOP will be sent, the next message will
* fail.
*/
cmd |= I2CM_CS_RUN;
if (priv->msgc < 2 && priv->mcnt < 2)
if (priv->mcnt < 2)
{
/* This is the last byte of the last message... add the STOP bit */
/* Are there more messages in this sequence? */
cmd |= I2CM_CS_STOP;
if (priv->msgc < 2)
{
/* No.. send the STOP */
cmd |= I2CM_CS_STOP;
}
else
{
/* Yes.. peek at the next message */
struct i2c_msg_s *curr = priv->msgv;
struct i2c_msg_s *next = curr + 1;
/* Same address as the current message? */
if (curr->addr != next->addr)
{
/* No.. send the STOP */
cmd |= I2CM_CS_STOP;
}
}
}
/* Set up to transfer the next byte. Are we sending or receiving? */
if ((priv->mflags & I2C_M_READ) != 0)
{
/* We are receiving data. Write the command to the control register to
* receive the next byte.
/* We are receiving data. We need to ACK UNLESS we are going to send
* STOP.
*/
cmd |= I2CM_CS_ACK;
if ((cmd & I2CM_CS_STOP) == 0)
{
cmd |= I2CM_CS_ACK;
}
/* Write the command to the control register to receive the next byte. */
tiva_i2c_putreg(priv, TIVA_I2CM_CS_OFFSET, cmd);
tiva_i2c_traceevent(priv, I2CEVENT_RECVSETUP, priv->mcnt);
@ -2078,6 +2116,7 @@ int up_i2cuninitialize(struct i2c_dev_s *dev)
/* Yes.. Disable power and other HW resource (GPIO's) */
tiva_i2c_uninitialize(priv);
priv->refs = 0;
/* Release unused resources */