From: Maximilian Luz luzmaximilian@gmail.com
[ Upstream commit d9a477f643eb3de71fbea5ae6103b800ceb8f547 ]
Currently, we check any received packet whether we have already seen it previously, regardless of the packet type (sequenced / unsequenced). We do this by checking the sequence number. This assumes that sequence numbers are valid for both sequenced and unsequenced packets. However, this assumption appears to be incorrect.
On some devices, the sequence number field of unsequenced packets (in particular HID input events on the Surface Pro 9) is always zero. As a result, the current retransmission check kicks in and discards all but the first unsequenced packet, breaking (among other things) keyboard and touchpad input.
Note that we have, so far, only seen packets being retransmitted in sequenced communication. In particular, this happens when there is an ACK timeout, causing the EC (or us) to re-send the packet waiting for an ACK. Arguably, retransmission / duplication of unsequenced packets should not be an issue as there is no logical condition (such as an ACK timeout) to determine when a packet should be sent again.
Therefore, remove the retransmission check for unsequenced packets entirely to resolve the issue.
Fixes: c167b9c7e3d6 ("platform/surface: Add Surface Aggregator subsystem") Signed-off-by: Maximilian Luz luzmaximilian@gmail.com Link: https://lore.kernel.org/r/20221113185951.224759-1-luzmaximilian@gmail.com Reviewed-by: Hans de Goede hdegoede@redhat.com Signed-off-by: Hans de Goede hdegoede@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- .../surface/aggregator/ssh_packet_layer.c | 24 +++++++++++++++---- 1 file changed, 20 insertions(+), 4 deletions(-)
diff --git a/drivers/platform/surface/aggregator/ssh_packet_layer.c b/drivers/platform/surface/aggregator/ssh_packet_layer.c index 8a4451c1ffe5..a652c2763175 100644 --- a/drivers/platform/surface/aggregator/ssh_packet_layer.c +++ b/drivers/platform/surface/aggregator/ssh_packet_layer.c @@ -1596,16 +1596,32 @@ static void ssh_ptl_timeout_reap(struct work_struct *work) ssh_ptl_tx_wakeup_packet(ptl); }
-static bool ssh_ptl_rx_retransmit_check(struct ssh_ptl *ptl, u8 seq) +static bool ssh_ptl_rx_retransmit_check(struct ssh_ptl *ptl, const struct ssh_frame *frame) { int i;
+ /* + * Ignore unsequenced packets. On some devices (notably Surface Pro 9), + * unsequenced events will always be sent with SEQ=0x00. Attempting to + * detect retransmission would thus just block all events. + * + * While sequence numbers would also allow detection of retransmitted + * packets in unsequenced communication, they have only ever been used + * to cover edge-cases in sequenced transmission. In particular, the + * only instance of packets being retransmitted (that we are aware of) + * is due to an ACK timeout. As this does not happen in unsequenced + * communication, skip the retransmission check for those packets + * entirely. + */ + if (frame->type == SSH_FRAME_TYPE_DATA_NSQ) + return false; + /* * Check if SEQ has been seen recently (i.e. packet was * re-transmitted and we should ignore it). */ for (i = 0; i < ARRAY_SIZE(ptl->rx.blocked.seqs); i++) { - if (likely(ptl->rx.blocked.seqs[i] != seq)) + if (likely(ptl->rx.blocked.seqs[i] != frame->seq)) continue;
ptl_dbg(ptl, "ptl: ignoring repeated data packet\n"); @@ -1613,7 +1629,7 @@ static bool ssh_ptl_rx_retransmit_check(struct ssh_ptl *ptl, u8 seq) }
/* Update list of blocked sequence IDs. */ - ptl->rx.blocked.seqs[ptl->rx.blocked.offset] = seq; + ptl->rx.blocked.seqs[ptl->rx.blocked.offset] = frame->seq; ptl->rx.blocked.offset = (ptl->rx.blocked.offset + 1) % ARRAY_SIZE(ptl->rx.blocked.seqs);
@@ -1624,7 +1640,7 @@ static void ssh_ptl_rx_dataframe(struct ssh_ptl *ptl, const struct ssh_frame *frame, const struct ssam_span *payload) { - if (ssh_ptl_rx_retransmit_check(ptl, frame->seq)) + if (ssh_ptl_rx_retransmit_check(ptl, frame)) return;
ptl->ops.data_received(ptl, payload);