[PATCH] typec: tcpm: fusb302: Resolve out of order messaging events

From: Adam Thomson
Date: Thu Nov 16 2017 - 10:45:17 EST

The expectation in the FUSB302 driver is that a TX_SUCCESS event
should occur after a message has been sent, but before a GCRCSENT
event is raised to indicate successful receipt of a message from
the partner. However in some circumstances it is possible to see
the hardware raise a GCRCSENT event before a TX_SUCCESS event
is raised. The upshot of this is that the GCRCSENT handling portion
of code ends up reporting the GoodCRC message to TCPM because the
TX_SUCCESS event hasn't yet arrived to trigger a consumption of it.
When TX_SUCCESS is then raised by the chip it ends up consuming the
actual message that was meant for TCPM, and this incorrect sequence
results in a hard reset from TCPM.

To avoid this problem, this commit moves all FIFO reading to be
done based on a GCRCSENT event, and when reading from the FIFO
any GoodCRC messages read in are discarded so only valid messages
are reported to TCPM.

Patch is based on Linux next-20171114 to include move out of staging.

Signed-off-by: Adam Thomson <Adam.Thomson.Opensource@xxxxxxxxxxx>
drivers/usb/typec/fusb302/fusb302.c | 17 +++++++++++------
1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/usb/typec/fusb302/fusb302.c b/drivers/usb/typec/fusb302/fusb302.c
index 72cb060..48a7ff4 100644
--- a/drivers/usb/typec/fusb302/fusb302.c
+++ b/drivers/usb/typec/fusb302/fusb302.c
@@ -1650,12 +1650,6 @@ static irqreturn_t fusb302_irq_intn(int irq, void *dev_id)

fusb302_log(chip, "IRQ: PD tx success");
- /* read out the received good CRC */
- ret = fusb302_pd_read_message(chip, &pd_msg);
- if (ret < 0) {
- fusb302_log(chip, "cannot read in GCRC, ret=%d", ret);
- goto done;
- }
tcpm_pd_transmit_complete(chip->tcpm_port, TCPC_TX_SUCCESS);

@@ -1671,12 +1665,23 @@ static irqreturn_t fusb302_irq_intn(int irq, void *dev_id)

fusb302_log(chip, "IRQ: PD sent good CRC");
ret = fusb302_pd_read_message(chip, &pd_msg);
if (ret < 0) {
"cannot read in PD message, ret=%d", ret);
goto done;
+ /*
+ * Check to make sure we've not read off a GoodCRC message.
+ * If so then read again to retrieve expected message
+ */
+ if ((!(pd_msg.header & PD_HEADER_EXT_HDR)) &&
+ (!pd_header_cnt_le(pd_msg.header)) &&
+ (pd_header_type_le(pd_msg.header) == PD_CTRL_GOOD_CRC))
+ goto retry;
tcpm_pd_receive(chip->tcpm_port, &pd_msg);