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| /freebsd-11-stable/sys/dev/ath/ | ||
| H A D | if_ath_tx.c | diff 251014 Sun May 26 20:34:37 MDT 2013 adrian Migrate ath(4) to now use if_transmit instead of the legacy if_start and if queue mechanism; also fix up (non-11n) TX fragment handling. This may result in a bit of a performance drop for now but I plan on debugging and resolving this at a later stage. Whilst here, fix the transmit path so fragment transmission works. The TX fragmentation handling is a bit more special. In order to correctly transmit TX fragments, there's a bunch of corner cases that need to be handled: * They must be transmitted back to back, in the same order.. * .. ie, you need to hold the TX lock whilst transmitting this set of fragments rather than interleaving it with other MSDUs destined to other nodes; * The length of the next fragment is required when transmitting, in order to correctly set the NAV field in the current frame to the length of the next frame; which requires .. * .. that we know the transmit duration of the next frame, which .. * .. requires us to set the rate of all fragments to the same length, or make the decision up-front, etc. To facilitate this, I've added a new ath_buf field to describe the length of the next fragment. This avoids having to keep the mbuf chain together. This used to work before my 11n TX path work because the ath_tx_start() routine would be handed a single mbuf with m_nextpkt pointing to the next frame, and that would be maintained all the way up to when the duration calculation was done. This doesn't hold true any longer - the actual queuing may occur at any point in the future (think ath_node TID software queuing) so this information needs to be maintained. Right now this does work for non-11n frames but it doesn't at all enforce the same rate control decision for all frames in the fragment. I plan on fixing this in a followup commit. RTS/CTS has the same issue, I'll look at fixing this in a subsequent commit. Finaly, 11n fragment support requires the driver to have fully decided what the rate scenario setup is - including 20/40MHz, short/long GI, STBC, LDPC, number of streams, etc. Right now that decision is (currently) made _after_ the NAV field value is updated. I'll fix all of this in subsequent commits. Tested: * AR5416, STA, transmitting 11abg fragments * AR5416, STA, 11n fragments work but the NAV field is incorrect for the reasons above. TODO: * It would be nice to be able to queue mbufs per-node and per-TID so we can only queue ath_buf entries when it's time to assemble frames to send to the hardware. But honestly, we should just do that level of software queue management in net80211 rather than ath(4), so I'm going to leave this alone for now. * More thorough AP, mesh and adhoc testing. * Ensure that net80211 doesn't hand us fragmented frames when A-MPDU has been negotiated, as we can't do software retransmission of fragments. * .. set CLRDMASK when transmitting fragments, just to ensure. |
| H A D | if_ath.c | diff 251014 Sun May 26 20:34:37 MDT 2013 adrian Migrate ath(4) to now use if_transmit instead of the legacy if_start and if queue mechanism; also fix up (non-11n) TX fragment handling. This may result in a bit of a performance drop for now but I plan on debugging and resolving this at a later stage. Whilst here, fix the transmit path so fragment transmission works. The TX fragmentation handling is a bit more special. In order to correctly transmit TX fragments, there's a bunch of corner cases that need to be handled: * They must be transmitted back to back, in the same order.. * .. ie, you need to hold the TX lock whilst transmitting this set of fragments rather than interleaving it with other MSDUs destined to other nodes; * The length of the next fragment is required when transmitting, in order to correctly set the NAV field in the current frame to the length of the next frame; which requires .. * .. that we know the transmit duration of the next frame, which .. * .. requires us to set the rate of all fragments to the same length, or make the decision up-front, etc. To facilitate this, I've added a new ath_buf field to describe the length of the next fragment. This avoids having to keep the mbuf chain together. This used to work before my 11n TX path work because the ath_tx_start() routine would be handed a single mbuf with m_nextpkt pointing to the next frame, and that would be maintained all the way up to when the duration calculation was done. This doesn't hold true any longer - the actual queuing may occur at any point in the future (think ath_node TID software queuing) so this information needs to be maintained. Right now this does work for non-11n frames but it doesn't at all enforce the same rate control decision for all frames in the fragment. I plan on fixing this in a followup commit. RTS/CTS has the same issue, I'll look at fixing this in a subsequent commit. Finaly, 11n fragment support requires the driver to have fully decided what the rate scenario setup is - including 20/40MHz, short/long GI, STBC, LDPC, number of streams, etc. Right now that decision is (currently) made _after_ the NAV field value is updated. I'll fix all of this in subsequent commits. Tested: * AR5416, STA, transmitting 11abg fragments * AR5416, STA, 11n fragments work but the NAV field is incorrect for the reasons above. TODO: * It would be nice to be able to queue mbufs per-node and per-TID so we can only queue ath_buf entries when it's time to assemble frames to send to the hardware. But honestly, we should just do that level of software queue management in net80211 rather than ath(4), so I'm going to leave this alone for now. * More thorough AP, mesh and adhoc testing. * Ensure that net80211 doesn't hand us fragmented frames when A-MPDU has been negotiated, as we can't do software retransmission of fragments. * .. set CLRDMASK when transmitting fragments, just to ensure. |
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