ath9k_hw: optimize tx status descriptor processing

Disassembly shows, that at least on MIPS, the compiler generates a lot of
memory accesses to the same location in the descriptor field parsing.
Since it is operating on uncached memory, this can be quite expensive in
this hot path.
Change the code a bit to help the compiler optimize it properly, and get
rid of some unused fields in the ath_tx_status struct.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

diff --git a/drivers/net/wireless/ath/ath9k/ar9002_mac.c b/drivers/net/wireless/ath/ath9k/ar9002_mac.c
index f5ed73d..3b4c52c 100644 (file)
--- a/drivers/net/wireless/ath/ath9k/ar9002_mac.c
+++ b/drivers/net/wireless/ath/ath9k/ar9002_mac.c
@@ -208,77 +208,68 @@ static int ar9002_hw_proc_txdesc(struct ath_hw *ah, void *ds,
                                 struct ath_tx_status *ts)
 {
        struct ar5416_desc *ads = AR5416DESC(ds);
+       u32 status;
 
-       if ((ads->ds_txstatus9 & AR_TxDone) == 0)
+       status = ACCESS_ONCE(ads->ds_txstatus9);
+       if ((status & AR_TxDone) == 0)
                return -EINPROGRESS;
 
-       ts->ts_seqnum = MS(ads->ds_txstatus9, AR_SeqNum);
        ts->ts_tstamp = ads->AR_SendTimestamp;
        ts->ts_status = 0;
        ts->ts_flags = 0;
 
-       if (ads->ds_txstatus1 & AR_FrmXmitOK)
+       if (status & AR_TxOpExceeded)
+               ts->ts_status |= ATH9K_TXERR_XTXOP;
+       ts->tid = MS(status, AR_TxTid);
+       ts->ts_rateindex = MS(status, AR_FinalTxIdx);
+       ts->ts_seqnum = MS(status, AR_SeqNum);
+
+       status = ACCESS_ONCE(ads->ds_txstatus0);
+       ts->ts_rssi_ctl0 = MS(status, AR_TxRSSIAnt00);
+       ts->ts_rssi_ctl1 = MS(status, AR_TxRSSIAnt01);
+       ts->ts_rssi_ctl2 = MS(status, AR_TxRSSIAnt02);
+       if (status & AR_TxBaStatus) {
+               ts->ts_flags |= ATH9K_TX_BA;
+               ts->ba_low = ads->AR_BaBitmapLow;
+               ts->ba_high = ads->AR_BaBitmapHigh;
+       }
+
+       status = ACCESS_ONCE(ads->ds_txstatus1);
+       if (status & AR_FrmXmitOK)
                ts->ts_status |= ATH9K_TX_ACKED;
-       if (ads->ds_txstatus1 & AR_ExcessiveRetries)
+       if (status & AR_ExcessiveRetries)
                ts->ts_status |= ATH9K_TXERR_XRETRY;
-       if (ads->ds_txstatus1 & AR_Filtered)
+       if (status & AR_Filtered)
                ts->ts_status |= ATH9K_TXERR_FILT;
-       if (ads->ds_txstatus1 & AR_FIFOUnderrun) {
+       if (status & AR_FIFOUnderrun) {
                ts->ts_status |= ATH9K_TXERR_FIFO;
                ath9k_hw_updatetxtriglevel(ah, true);
        }
-       if (ads->ds_txstatus9 & AR_TxOpExceeded)
-               ts->ts_status |= ATH9K_TXERR_XTXOP;
-       if (ads->ds_txstatus1 & AR_TxTimerExpired)
+       if (status & AR_TxTimerExpired)
                ts->ts_status |= ATH9K_TXERR_TIMER_EXPIRED;
-
-       if (ads->ds_txstatus1 & AR_DescCfgErr)
+       if (status & AR_DescCfgErr)
                ts->ts_flags |= ATH9K_TX_DESC_CFG_ERR;
-       if (ads->ds_txstatus1 & AR_TxDataUnderrun) {
+       if (status & AR_TxDataUnderrun) {
                ts->ts_flags |= ATH9K_TX_DATA_UNDERRUN;
                ath9k_hw_updatetxtriglevel(ah, true);
        }
-       if (ads->ds_txstatus1 & AR_TxDelimUnderrun) {
+       if (status & AR_TxDelimUnderrun) {
                ts->ts_flags |= ATH9K_TX_DELIM_UNDERRUN;
                ath9k_hw_updatetxtriglevel(ah, true);
        }
-       if (ads->ds_txstatus0 & AR_TxBaStatus) {
-               ts->ts_flags |= ATH9K_TX_BA;
-               ts->ba_low = ads->AR_BaBitmapLow;
-               ts->ba_high = ads->AR_BaBitmapHigh;
-       }
+       ts->ts_shortretry = MS(status, AR_RTSFailCnt);
+       ts->ts_longretry = MS(status, AR_DataFailCnt);
+       ts->ts_virtcol = MS(status, AR_VirtRetryCnt);
 
-       ts->ts_rateindex = MS(ads->ds_txstatus9, AR_FinalTxIdx);
-       switch (ts->ts_rateindex) {
-       case 0:
-               ts->ts_ratecode = MS(ads->ds_ctl3, AR_XmitRate0);
-               break;
-       case 1:
-               ts->ts_ratecode = MS(ads->ds_ctl3, AR_XmitRate1);
-               break;
-       case 2:
-               ts->ts_ratecode = MS(ads->ds_ctl3, AR_XmitRate2);
-               break;
-       case 3:
-               ts->ts_ratecode = MS(ads->ds_ctl3, AR_XmitRate3);
-               break;
-       }
+       status = ACCESS_ONCE(ads->ds_txstatus5);
+       ts->ts_rssi = MS(status, AR_TxRSSICombined);
+       ts->ts_rssi_ext0 = MS(status, AR_TxRSSIAnt10);
+       ts->ts_rssi_ext1 = MS(status, AR_TxRSSIAnt11);
+       ts->ts_rssi_ext2 = MS(status, AR_TxRSSIAnt12);
 
-       ts->ts_rssi = MS(ads->ds_txstatus5, AR_TxRSSICombined);
-       ts->ts_rssi_ctl0 = MS(ads->ds_txstatus0, AR_TxRSSIAnt00);
-       ts->ts_rssi_ctl1 = MS(ads->ds_txstatus0, AR_TxRSSIAnt01);
-       ts->ts_rssi_ctl2 = MS(ads->ds_txstatus0, AR_TxRSSIAnt02);
-       ts->ts_rssi_ext0 = MS(ads->ds_txstatus5, AR_TxRSSIAnt10);
-       ts->ts_rssi_ext1 = MS(ads->ds_txstatus5, AR_TxRSSIAnt11);
-       ts->ts_rssi_ext2 = MS(ads->ds_txstatus5, AR_TxRSSIAnt12);
        ts->evm0 = ads->AR_TxEVM0;
        ts->evm1 = ads->AR_TxEVM1;
        ts->evm2 = ads->AR_TxEVM2;
-       ts->ts_shortretry = MS(ads->ds_txstatus1, AR_RTSFailCnt);
-       ts->ts_longretry = MS(ads->ds_txstatus1, AR_DataFailCnt);
-       ts->ts_virtcol = MS(ads->ds_txstatus1, AR_VirtRetryCnt);
-       ts->tid = MS(ads->ds_txstatus9, AR_TxTid);
-       ts->ts_antenna = 0;
 
        return 0;
 }

diff --git a/drivers/net/wireless/ath/ath9k/ar9003_mac.c b/drivers/net/wireless/ath/ath9k/ar9003_mac.c
index 3b424ca..10c812e 100644 (file)
--- a/drivers/net/wireless/ath/ath9k/ar9003_mac.c
+++ b/drivers/net/wireless/ath/ath9k/ar9003_mac.c
@@ -237,10 +237,12 @@ static int ar9003_hw_proc_txdesc(struct ath_hw *ah, void *ds,
                                 struct ath_tx_status *ts)
 {
        struct ar9003_txs *ads;
+       u32 status;
 
        ads = &ah->ts_ring[ah->ts_tail];
 
-       if ((ads->status8 & AR_TxDone) == 0)
+       status = ACCESS_ONCE(ads->status8);
+       if ((status & AR_TxDone) == 0)
                return -EINPROGRESS;
 
        ah->ts_tail = (ah->ts_tail + 1) % ah->ts_size;
@@ -253,57 +255,58 @@ static int ar9003_hw_proc_txdesc(struct ath_hw *ah, void *ds,
                return -EIO;
        }
 
+       if (status & AR_TxOpExceeded)
+               ts->ts_status |= ATH9K_TXERR_XTXOP;
+       ts->ts_rateindex = MS(status, AR_FinalTxIdx);
+       ts->ts_seqnum = MS(status, AR_SeqNum);
+       ts->tid = MS(status, AR_TxTid);
+
        ts->qid = MS(ads->ds_info, AR_TxQcuNum);
        ts->desc_id = MS(ads->status1, AR_TxDescId);
-       ts->ts_seqnum = MS(ads->status8, AR_SeqNum);
        ts->ts_tstamp = ads->status4;
        ts->ts_status = 0;
        ts->ts_flags  = 0;
 
-       if (ads->status3 & AR_ExcessiveRetries)
+       status = ACCESS_ONCE(ads->status2);
+       ts->ts_rssi_ctl0 = MS(status, AR_TxRSSIAnt00);
+       ts->ts_rssi_ctl1 = MS(status, AR_TxRSSIAnt01);
+       ts->ts_rssi_ctl2 = MS(status, AR_TxRSSIAnt02);
+       if (status & AR_TxBaStatus) {
+               ts->ts_flags |= ATH9K_TX_BA;
+               ts->ba_low = ads->status5;
+               ts->ba_high = ads->status6;
+       }
+
+       status = ACCESS_ONCE(ads->status3);
+       if (status & AR_ExcessiveRetries)
                ts->ts_status |= ATH9K_TXERR_XRETRY;
-       if (ads->status3 & AR_Filtered)
+       if (status & AR_Filtered)
                ts->ts_status |= ATH9K_TXERR_FILT;
-       if (ads->status3 & AR_FIFOUnderrun) {
+       if (status & AR_FIFOUnderrun) {
                ts->ts_status |= ATH9K_TXERR_FIFO;
                ath9k_hw_updatetxtriglevel(ah, true);
        }
-       if (ads->status8 & AR_TxOpExceeded)
-               ts->ts_status |= ATH9K_TXERR_XTXOP;
-       if (ads->status3 & AR_TxTimerExpired)
+       if (status & AR_TxTimerExpired)
                ts->ts_status |= ATH9K_TXERR_TIMER_EXPIRED;
-
-       if (ads->status3 & AR_DescCfgErr)
+       if (status & AR_DescCfgErr)
                ts->ts_flags |= ATH9K_TX_DESC_CFG_ERR;
-       if (ads->status3 & AR_TxDataUnderrun) {
+       if (status & AR_TxDataUnderrun) {
                ts->ts_flags |= ATH9K_TX_DATA_UNDERRUN;
                ath9k_hw_updatetxtriglevel(ah, true);
        }
-       if (ads->status3 & AR_TxDelimUnderrun) {
+       if (status & AR_TxDelimUnderrun) {
                ts->ts_flags |= ATH9K_TX_DELIM_UNDERRUN;
                ath9k_hw_updatetxtriglevel(ah, true);
        }
-       if (ads->status2 & AR_TxBaStatus) {
-               ts->ts_flags |= ATH9K_TX_BA;
-               ts->ba_low = ads->status5;
-               ts->ba_high = ads->status6;
-       }
-
-       ts->ts_rateindex = MS(ads->status8, AR_FinalTxIdx);
-
-       ts->ts_rssi = MS(ads->status7, AR_TxRSSICombined);
-       ts->ts_rssi_ctl0 = MS(ads->status2, AR_TxRSSIAnt00);
-       ts->ts_rssi_ctl1 = MS(ads->status2, AR_TxRSSIAnt01);
-       ts->ts_rssi_ctl2 = MS(ads->status2, AR_TxRSSIAnt02);
-       ts->ts_rssi_ext0 = MS(ads->status7, AR_TxRSSIAnt10);
-       ts->ts_rssi_ext1 = MS(ads->status7, AR_TxRSSIAnt11);
-       ts->ts_rssi_ext2 = MS(ads->status7, AR_TxRSSIAnt12);
-       ts->ts_shortretry = MS(ads->status3, AR_RTSFailCnt);
-       ts->ts_longretry = MS(ads->status3, AR_DataFailCnt);
-       ts->ts_virtcol = MS(ads->status3, AR_VirtRetryCnt);
-       ts->ts_antenna = 0;
-
-       ts->tid = MS(ads->status8, AR_TxTid);
+       ts->ts_shortretry = MS(status, AR_RTSFailCnt);
+       ts->ts_longretry = MS(status, AR_DataFailCnt);
+       ts->ts_virtcol = MS(status, AR_VirtRetryCnt);
+
+       status = ACCESS_ONCE(ads->status7);
+       ts->ts_rssi = MS(status, AR_TxRSSICombined);
+       ts->ts_rssi_ext0 = MS(status, AR_TxRSSIAnt10);
+       ts->ts_rssi_ext1 = MS(status, AR_TxRSSIAnt11);
+       ts->ts_rssi_ext2 = MS(status, AR_TxRSSIAnt12);
 
        memset(ads, 0, sizeof(*ads));
 

diff --git a/drivers/net/wireless/ath/ath9k/mac.h b/drivers/net/wireless/ath/ath9k/mac.h
index 538c676..fdc2507 100644 (file)
--- a/drivers/net/wireless/ath/ath9k/mac.h
+++ b/drivers/net/wireless/ath/ath9k/mac.h
@@ -104,13 +104,11 @@ struct ath_tx_status {
        u32 ts_tstamp;
        u16 ts_seqnum;
        u8 ts_status;
-       u8 ts_ratecode;
        u8 ts_rateindex;
        int8_t ts_rssi;
        u8 ts_shortretry;
        u8 ts_longretry;
        u8 ts_virtcol;
-       u8 ts_antenna;
        u8 ts_flags;
        int8_t ts_rssi_ctl0;
        int8_t ts_rssi_ctl1;
@@ -121,7 +119,6 @@ struct ath_tx_status {
        u8 qid;
        u16 desc_id;
        u8 tid;
-       u8 pad[2];
        u32 ba_low;
        u32 ba_high;
        u32 evm0;