git: ff1e8581806f - main - twsi: support more message combinations in transfers
- Go to: [ bottom of page ] [ top of archives ] [ this month ]
Date: Fri, 26 Nov 2021 14:24:06 UTC
The branch main has been updated by avg:
URL: https://cgit.FreeBSD.org/src/commit/?id=ff1e8581806f70e54fecddf8a6a23488dc7b968a
commit ff1e8581806f70e54fecddf8a6a23488dc7b968a
Author: Andriy Gapon <avg@FreeBSD.org>
AuthorDate: 2021-11-26 09:48:21 +0000
Commit: Andriy Gapon <avg@FreeBSD.org>
CommitDate: 2021-11-26 14:20:27 +0000
twsi: support more message combinations in transfers
Most prominently, add support for a transfer where a write with no-stop
flag is followed by a write with no-start flag. Logically, it's a
single larger write, but consumers may want to split it like that
because one part can be a register ID and the other part can be data to
be written to (or starting at) that register.
Such a transfer can be created by i2c tool and iic(4) driver, e.g., for
an EEPROM write at specific offset:
i2c -m tr -a 0x50 -d w -w 16 -o 0 -c 8 -v < /dev/random
This should be fixed by new code that handles the end of data transfer
for both reads and writes. It handles two existing conditions and one
new. Namely:
- the last message has been completed -- end of transfer;
- a message has been completed and the next one requires the start
condition;
- a message has been completed and the next one should be sent without
the start condition.
In the last case we simply switch to the next message and start sending
its data. Reads without the start condition are not supported yet,
though. That's because we NACK the last byte of the previous message,
so the device stops sending data. To fix this we will need to add a
look-ahead at the next message when handling the penultimate byte of the
current one.
This change also fixed a bug where msg_idx was not incremented after a
read message. Apparently, typically a read message is a last message in
a transfer, so the bug did not cause much trouble.
PR: 258994
MFC after: 3 weeks
---
sys/dev/iicbus/twsi/twsi.c | 85 +++++++++++++++++++++++++++++-----------------
1 file changed, 53 insertions(+), 32 deletions(-)
diff --git a/sys/dev/iicbus/twsi/twsi.c b/sys/dev/iicbus/twsi/twsi.c
index 2f77e2dc69c3..ab0bb3f26961 100644
--- a/sys/dev/iicbus/twsi/twsi.c
+++ b/sys/dev/iicbus/twsi/twsi.c
@@ -559,9 +559,12 @@ twsi_intr(void *arg)
{
struct twsi_softc *sc;
uint32_t status;
- int transfer_done = 0;
+ bool message_done;
+ bool send_start;
sc = arg;
+ message_done = false;
+ send_start = false;
mtx_lock(&sc->mutex);
debugf(sc, "Got interrupt, current msg=%u\n", sc->msg_idx);
@@ -578,6 +581,7 @@ twsi_intr(void *arg)
goto end;
}
+restart:
switch (status) {
case TWSI_STATUS_START:
case TWSI_STATUS_RPTD_START:
@@ -636,38 +640,30 @@ twsi_intr(void *arg)
twsi_error(sc, IIC_ENOACK);
break;
case TWSI_STATUS_DATA_WR_ACK:
- debugf(sc, "Ack received after transmitting data\n");
+ KASSERT(sc->sent_bytes <= sc->msgs[sc->msg_idx].len,
+ ("sent_bytes beyond message length"));
+ debugf(sc, "ACK received after transmitting data\n");
if (sc->sent_bytes == sc->msgs[sc->msg_idx].len) {
- debugf(sc, "Done sending all the bytes for msg %d\n", sc->msg_idx);
+ debugf(sc, "Done TX data\n");
+
/* Send stop, no interrupts on stop */
if (!(sc->msgs[sc->msg_idx].flags & IIC_M_NOSTOP)) {
- debugf(sc, "Done TX data, send stop\n");
TWSI_WRITE(sc, sc->reg_control,
sc->control_val | TWSI_CONTROL_STOP);
} else {
- debugf(sc, "Done TX data with NO_STOP\n");
- TWSI_WRITE(sc, sc->reg_control, sc->control_val | TWSI_CONTROL_START);
- }
- sc->msg_idx++;
- if (sc->msg_idx == sc->nmsgs) {
- debugf(sc, "transfer_done=1\n");
- transfer_done = 1;
- sc->error = 0;
- } else {
- debugf(sc, "Send repeated start\n");
- TWSI_WRITE(sc, sc->reg_control, sc->control_val | TWSI_CONTROL_START);
+ debugf(sc, "NOSTOP flag\n");
}
- } else {
- debugf(sc, "Sending byte %d (of %d) = %x\n",
- sc->sent_bytes,
- sc->msgs[sc->msg_idx].len,
- sc->msgs[sc->msg_idx].buf[sc->sent_bytes]);
- TWSI_WRITE(sc, sc->reg_data,
- sc->msgs[sc->msg_idx].buf[sc->sent_bytes]);
- TWSI_WRITE(sc, sc->reg_control,
- sc->control_val);
- sc->sent_bytes++;
+ message_done = true;
+ break;
}
+
+ debugf(sc, "Sending byte %d (of %d) = 0x%x\n",
+ sc->sent_bytes,
+ sc->msgs[sc->msg_idx].len,
+ sc->msgs[sc->msg_idx].buf[sc->sent_bytes]);
+ TWSI_WRITE(sc, sc->reg_data,
+ sc->msgs[sc->msg_idx].buf[sc->sent_bytes]);
+ sc->sent_bytes++;
break;
case TWSI_STATUS_DATA_RD_ACK:
@@ -715,6 +711,7 @@ twsi_intr(void *arg)
TWSI_WRITE(sc, sc->reg_control,
sc->control_val | TWSI_CONTROL_STOP);
}
+ message_done = true;
} else {
/*
* We should not have NACK-ed yet.
@@ -723,9 +720,6 @@ twsi_intr(void *arg)
debugf(sc, "NACK-ed before receving all bytes?\n");
twsi_error(sc, IIC_ESTATUS);
}
- sc->transfer = 0;
- transfer_done = 1;
- sc->error = 0;
break;
case TWSI_STATUS_BUS_ERROR:
@@ -741,17 +735,44 @@ twsi_intr(void *arg)
twsi_error(sc, IIC_ESTATUS);
break;
}
- debugf(sc, "Refresh reg_control\n");
+ if (message_done) {
+ sc->msg_idx++;
+ if (sc->msg_idx == sc->nmsgs) {
+ debugf(sc, "All messages transmitted\n");
+ sc->transfer = 0;
+ sc->error = 0;
+ } else if ((sc->msgs[sc->msg_idx].flags & IIC_M_NOSTART) == 0) {
+ debugf(sc, "Send (repeated) start\n");
+ send_start = true;
+ } else {
+ /* Just keep transmitting data. */
+ KASSERT((sc->msgs[sc->msg_idx - 1].flags & IIC_M_NOSTOP) != 0,
+ ("NOSTART message after STOP"));
+ KASSERT((sc->msgs[sc->msg_idx].flags & IIC_M_RD) ==
+ (sc->msgs[sc->msg_idx - 1].flags & IIC_M_RD),
+ ("change of transfer direction without a START"));
+ debugf(sc, "NOSTART message after NOSTOP\n");
+ sc->sent_bytes = 0;
+ sc->recv_bytes = 0;
+ if ((sc->msgs[sc->msg_idx].flags & IIC_M_RD) == 0) {
+ status = TWSI_STATUS_ADDR_W_ACK;
+ goto restart;
+ } else {
+ debugf(sc, "Read+NOSTART unsupported\n");
+ twsi_error(sc, IIC_ESTATUS);
+ }
+ }
+ }
end:
/*
* Newer Allwinner chips clear IFLG after writing 1 to it.
*/
+ debugf(sc, "Refresh reg_control\n");
TWSI_WRITE(sc, sc->reg_control, sc->control_val |
- (sc->iflag_w1c ? TWSI_CONTROL_IFLG : 0));
+ (sc->iflag_w1c ? TWSI_CONTROL_IFLG : 0) |
+ (send_start ? TWSI_CONTROL_START : 0));
- if (transfer_done == 1)
- sc->transfer = 0;
debugf(sc, "Done with interrupt, transfer = %d\n", sc->transfer);
if (sc->transfer == 0)
wakeup(sc);