Re: Question on beacon-miss offloading.

[Ben Greear <greearb@candelatech.com>]

On 06/11/2015 11:03 PM, Michal Kazior wrote:
> On 12 June 2015 at 01:38, Ben Greear <greearb@candelatech.com> wrote:
>> On 06/11/2015 02:07 PM, Ben Greear wrote:
>>> In my ath10k CT firmware, I am disabling the beacon-miss offloading
>>> to save space and because it will not work with lots of virtual
>>> stations.
>>>
>>> But, it must be that I need some way to tell the stack that this
>>> feature is not enabled, because when suddenly kill my AP, then
>>> the ath10k station connected to it shows endless 'beacon loss' events
>>> in 'iw events' output, but it never actually loses connection.
>>>
>>> Stock firmware works fine, so probably I just need to disable
>>> some feature flag when registering the ath10k hardware
>>> when using CT firmware.
>>>
>>> With stock firmware, I see a quick dissassociation due to inactivity.
>>>
>>> I am having poor luck finding how a driver tells the stack
>>> it has beacon miss offload or not, so, does anyone know how
>>> this is controlled?
>>
>> I still am not sure why stock firmware works, but it appears
>> the reason mine is failing is that the ACK status for mgt frames
>> is always set to TRUE since the ath10k wmi-mgt-tx API is so
>> lame.  So, mac80211 does a probe, ath10k lies and says it was
>> acked, and mac80211 then things all is well for another few
>> seconds.
> 
> mac80211 shouldn't do a Probe Req to an AP on beacon loss because
> ath10k advertises it supports tx-status report. Hence mac80211 should
> use NullFunc frames which shouldn't go through wmi-mgmt-tx but htt
> tx-frm.
> 
> But then again: NullFunc status reporting via htt tx-frm was broken on
> 10.1 if memory serves right. I believe it was fixed in 10.2 or 10.2.4.
> 
> This problem has been effectively obscured on stock 10.1 by the
> offloaded beacon miss.

Thanks for the hint.  I was able to fix my firmware to properly
return htt tx status, and now it appears to work properly.

A quick throughput test works as well, so hopefully no regressions.

I guess the NulFunc related comment is incorrect for 10.1 stock firmware?

Maybe some others?

static void ath10k_tx_htt(struct ath10k *ar, struct sk_buff *skb)
{
	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
	int ret = 0;

	if (ar->htt.target_version_major >= 3) {
		/* Since HTT 3.0 there is no separate mgmt tx command */
		ret = ath10k_htt_tx(&ar->htt, skb);
		goto exit;
	}

	if (ieee80211_is_mgmt(hdr->frame_control)) {
		if (test_bit(ATH10K_FW_FEATURE_HAS_WMI_MGMT_TX,
			     ar->fw_features)) {
			if (skb_queue_len(&ar->wmi_mgmt_tx_queue) >=
			    ATH10K_MAX_NUM_MGMT_PENDING) {
				ath10k_warn(ar, "reached WMI management transmit queue limit\n");
				ret = -EBUSY;
				goto exit;
			}

			skb_queue_tail(&ar->wmi_mgmt_tx_queue, skb);
			ieee80211_queue_work(ar->hw, &ar->wmi_mgmt_tx_work);
		} else {
			ret = ath10k_htt_mgmt_tx(&ar->htt, skb);
		}
	} else if (!test_bit(ATH10K_FW_FEATURE_HAS_WMI_MGMT_TX,
			     ar->fw_features) &&
		   ieee80211_is_nullfunc(hdr->frame_control)) {
		/* FW does not report tx status properly for NullFunc frames
		 * unless they are sent through mgmt tx path. mac80211 sends
		 * those frames when it detects link/beacon loss and depends
		 * on the tx status to be correct. */
		ret = ath10k_htt_mgmt_tx(&ar->htt, skb);
	} else {
		ret = ath10k_htt_tx(&ar->htt, skb);
	}


Thanks,
Ben

-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com