/*
* theory of operation:
*
* c_can core saves a received CAN message into the first free message
* object it finds free (starting with the lowest). Bits NEWDAT and
* INTPND are set for this message object indicating that a new message
* has arrived. To work-around this issue, we keep two groups of message
* objects whose partitioning is defined by C_CAN_MSG_OBJ_RX_SPLIT.
*
* To ensure in-order frame reception we use the following
* approach while re-activating a message object to receive further
* frames:
* - if the current message object number is lower than
* C_CAN_MSG_RX_LOW_LAST, do not clear the NEWDAT bit while clearing
* the INTPND bit.
* - if the current message object number is equal to
* C_CAN_MSG_RX_LOW_LAST then clear the NEWDAT bit of all lower
* receive message objects.
* - if the current message object number is greater than
* C_CAN_MSG_RX_LOW_LAST then clear the NEWDAT bit of
* only this message object.
*/
static int c_can_do_rx_poll(struct net_device *dev, int quota)
{
u32 num_rx_pkts = 0;
unsigned int msg_obj, msg_ctrl_save;
struct c_can_priv *priv = netdev_priv(dev);
u32 val = c_can_read_reg32(priv, C_CAN_INTPND1_REG);
for (msg_obj = C_CAN_MSG_OBJ_RX_FIRST;
msg_obj <= C_CAN_MSG_OBJ_RX_LAST && quota > 0;
val = c_can_read_reg32(priv, C_CAN_INTPND1_REG),
msg_obj++) {
/*
* as interrupt pending register's bit n-1 corresponds to
* message object n, we need to handle the same properly.
*/
if (val & (1 << (msg_obj - 1))) {
c_can_object_get(dev, 0, msg_obj, IF_COMM_ALL &
~IF_COMM_TXRQST);
msg_ctrl_save = priv->read_reg(priv,
C_CAN_IFACE(MSGCTRL_REG, 0));
if (msg_ctrl_save & IF_MCONT_EOB)
return num_rx_pkts;
if (msg_ctrl_save & IF_MCONT_MSGLST) {
c_can_handle_lost_msg_obj(dev, 0, msg_obj);
num_rx_pkts++;
quota--;
continue;
}
if (!(msg_ctrl_save & IF_MCONT_NEWDAT))
continue;
/* read the data from the message object */
c_can_read_msg_object(dev, 0, msg_ctrl_save);
if (msg_obj < C_CAN_MSG_RX_LOW_LAST)
c_can_mark_rx_msg_obj(dev, 0,
msg_ctrl_save, msg_obj);
else if (msg_obj > C_CAN_MSG_RX_LOW_LAST)
/* activate this msg obj */
c_can_activate_rx_msg_obj(dev, 0,
msg_ctrl_save, msg_obj);
else if (msg_obj == C_CAN_MSG_RX_LOW_LAST)
/* activate all lower message objects */
c_can_activate_all_lower_rx_msg_obj(dev,
0, msg_ctrl_save);
num_rx_pkts++;
quota--;
}
}
return num_rx_pkts;
}
static int c_can_read_objects(struct net_device *dev, struct c_can_priv *priv,
u32 pend, int quota)
{
u32 pkts = 0, ctrl, obj;
while ((obj = ffs(pend)) && quota > 0) {
pend &= ~BIT(obj - 1);
c_can_rx_object_get(dev, priv, obj);
ctrl = priv->read_reg(priv, C_CAN_IFACE(MSGCTRL_REG, IF_RX));
if (ctrl & IF_MCONT_MSGLST) {
int n = c_can_handle_lost_msg_obj(dev, IF_RX, obj, ctrl);
pkts += n;
quota -= n;
continue;
}
/*
* This really should not happen, but this covers some
* odd HW behaviour. Do not remove that unless you
* want to brick your machine.
*/
if (!(ctrl & IF_MCONT_NEWDAT))
continue;
/* read the data from the message object */
c_can_read_msg_object(dev, IF_RX, ctrl);
c_can_rx_finalize(dev, priv, obj);
pkts++;
quota--;
}
return pkts;
}
