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>

3 files changed, 72 insertions, 81 deletions

diff --git a/drivers/net/wireless/ath/ath9k/ar9002_mac.c b/drivers/net/wireless/ath/ath9k/ar9002_mac.c
index f5ed73dac254..3b4c52c9181c 100644
--- 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 3b424ca1ba84..10c812e353a6 100644
--- 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 538c676e799c..fdc25074ca1f 100644
--- 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;