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fm10k: comment next_vf_mbx flow 

Add a header comment explaining why we have the somewhat crazy mailbox
flow. This flow is necessary as it prevents the PF<->SM mailbox from
being flooded by the VF messages, which normally trigger a message to
the PF. This helps prevent the case where we see a PF mailbox timeout.

Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Acked-by: Matthew Vick <matthew.vick@intel.com>
Tested-by: Krishneil Singh <krishneil.k.singh@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
This commit is contained in:
Jeff Kirsher 2015-04-03 13:27:07 -07:00
parent 9de15bda37
commit ada2411d4f
1 changed files with 11 additions and 0 deletions
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11
drivers/net/ethernet/intel/fm10k/fm10k_iov.c
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@ -113,6 +113,13 @@ s32 fm10k_iov_mbx(struct fm10k_intfc *interface)
/* lock the mailbox for transmit and receive */
fm10k_mbx_lock(interface);
/* Most VF messages sent to the PF cause the PF to respond by
* requesting from the SM mailbox. This means that too many VF
* messages processed at once could cause a mailbox timeout on the PF.
* To prevent this, store a pointer to the next VF mbx to process. Use
* that as the start of the loop so that we don't starve whichever VF
* got ignored on the previous run.
*/
process_mbx:
for (i = iov_data->next_vf_mbx ? : iov_data->num_vfs; i--;) {
struct fm10k_vf_info *vf_info = &iov_data->vf_info[i];
@ -137,6 +144,10 @@ s32 fm10k_iov_mbx(struct fm10k_intfc *interface)
mbx->ops.process(hw, mbx);
}
/* if we stopped processing mailboxes early, update next_vf_mbx.
* Otherwise, reset next_vf_mbx, and restart loop so that we process
* the remaining mailboxes we skipped at the start.
*/
if (i >= 0) {
iov_data->next_vf_mbx = i + 1;
} else if (iov_data->next_vf_mbx) {