When the target needs more time to process the received PDU, it sends
Response Timeout Extension (RTOX) PDU.

When the initiator receives a RTOX PDU, it must reply with a RTOX PDU
and extends the current rwt value with the formula:
 rwt_int = rwt * rtox

This patch takes care of the rtox value passed by the target in the RTOX
PDU and extends the timeout for the next response accordingly.

Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

When sending an ATR_REQ, the initiator must wait for the ATR_RES at
least 'RWT(nfcdep,activation) + dRWT(nfcdep)' and no more than
'RWT(nfcdep,activation) + dRWT(nfcdep) + dT(nfcdep,initiator)'. This
gives a timeout value between 1237 ms and 1337 ms. This patch defines
DIGITAL_ATR_RES_RWT to 1337 used for the timeout value of ATR_REQ
command.

For other DEP PDUs, the initiator must wait between 'RWT + dRWT(nfcdep)'
and 'RWT + dRWT(nfcdep) + dT(nfcdep,initiator)' where RWT is given by
the following formula: '(256 * 16 / f(c)) * 2^wt' where wt is the value
of the TO field in the ATR_RES response and is in the range between 0
and 14. This patch declares a mapping table for wt values and gives RWT
max values between 100 ms and 5049 ms.

This patch also defines DIGITAL_ATR_RES_TO_WT, the maximum wt value in
target mode, to 8.

Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

This patch frees the RTOX resp sk_buff in initiator mode. It also makes
use of the free_resp exit point for ATN supervisor PDUs in both
initiator and target mode.

Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

With this patch, ACK PDU sk_buffs are now freed and code has been
refactored for better errors handling.

Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

When the target receives a NACK PDU, it re-sends the last sent PDU.

ACK PDUs are received by the target as a reply from the initiator to
chained I-PDUs. There are 3 cases to handle:
- If the target has previously received 1 or more ATN PDUs and the PNI
  in the ACK PDU is equal to the target PNI - 1, then it means that the
  initiator did not received the last issued PDU from the target. In
  this case it re-sends this PDU.
- If the target has received 1 or more ATN PDUs but the ACK PNI is not
  the target PNI - 1, then this means that this ACK is the reply of the
  previous chained I-PDU sent by the target. The target did not received
  it on the first attempt and it is being re-sent by the initiator. The
  process continues as usual.
- No ATN PDU received before this ACK PDU. This is the reply of a
  chained I-PDU. The target keeps on processing its chained I-PDU.

The code has been refactored to avoid too many indentation levels.

Also, ACK and NACK PDUs were not freed. This is now fixed.

Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

When the initiator sends a DEP_REQ I-PDU, the target device may not
reply in a timely manner. In this case the initiator device must send an
attention PDU (ATN) and if the recipient replies with an ATN PDU in
return, then the last I-PDU must be sent again by the initiator.

This patch fixes how the target handles I-PDU received after an ATN PDU
has been received.

There are 2 possible cases:
- The target has received the initial DEP_REQ and sends back the DEP_RES
  but the initiator did not receive it. In this case, after the
  initiator has sent an ATN PDU and the target replied it (with an ATN
  as well), the initiator sends the saved skb of the initial DEP_REQ
  again and the target replies with the saved skb of the initial
  DEP_RES.
- Or the target did not even received the initial DEP_REQ. In this case,
  after the ATN PDUs exchange, the initiator sends the saved skb and the
  target simply passes it up, just as usual.

This behavior is controlled using the atn_count and the PNI field of the
digital device structure.

Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

When allocating chained I-PDUs, there is no need to call skb_reserve()
since it's already done by digital_alloc_skb() and contains enough room
for the driver head and tail data.

Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

This patch fixes the way an I-PDU is saved in case it needs to be sent
again. It is now copied using pskb_copy() and not simply referenced
using skb_get() since it could be modified by the driver.

digital_in_send_saved_skb() and digital_tg_send_saved_skb() still get a
reference on the saved skb which is re-sent but release it if the send
operation fails. That way the caller doesn't have to take care about skb
ref in case of error.

RTOX supervisor PDU must not be saved as this can override a previously
saved I-PDU that should be re-sent later on.

Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

With this patch, the Digital Protocol layer abort the last issued
command when the dep link goes down. That way it does not have to wait
for the driver to reply with a timeout error before sending a new
command (i.e. a start poll command if constant polling is on).

Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

There is a flag in the command structure indicating that this command is
pending. It was checked before sending the command to not send the same
command twice but it was actually never set. This is now fixed.

Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>