ath5k: optimize tx status processing

Use ACCESS_ONCE to reduce the number of variable reloads on uncached memory

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

diff --git a/drivers/net/wireless/ath/ath5k/desc.c b/drivers/net/wireless/ath/ath5k/desc.c
index 990a3b4..3758b96 100644 (file)
--- a/drivers/net/wireless/ath/ath5k/desc.c
+++ b/drivers/net/wireless/ath/ath5k/desc.c
@@ -401,32 +401,38 @@ static int ath5k_hw_proc_4word_tx_status(struct ath5k_hw *ah,
 {
        struct ath5k_hw_4w_tx_ctl *tx_ctl;
        struct ath5k_hw_tx_status *tx_status;
+       u32 txstat0, txstat1, txctl2;
 
        tx_ctl = &desc->ud.ds_tx5212.tx_ctl;
        tx_status = &desc->ud.ds_tx5212.tx_stat;
 
+       txstat1 = ACCESS_ONCE(tx_status->tx_status_1);
+
        /* No frame has been send or error */
-       if (unlikely(!(tx_status->tx_status_1 & AR5K_DESC_TX_STATUS1_DONE)))
+       if (unlikely(!(txstat1 & AR5K_DESC_TX_STATUS1_DONE)))
                return -EINPROGRESS;
 
+       txstat0 = ACCESS_ONCE(tx_status->tx_status_0);
+       txctl2 = ACCESS_ONCE(tx_ctl->tx_control_2);
+
        /*
         * Get descriptor status
         */
-       ts->ts_tstamp = AR5K_REG_MS(tx_status->tx_status_0,
+       ts->ts_tstamp = AR5K_REG_MS(txstat0,
                AR5K_DESC_TX_STATUS0_SEND_TIMESTAMP);
-       ts->ts_shortretry = AR5K_REG_MS(tx_status->tx_status_0,
+       ts->ts_shortretry = AR5K_REG_MS(txstat0,
                AR5K_DESC_TX_STATUS0_SHORT_RETRY_COUNT);
-       ts->ts_longretry = AR5K_REG_MS(tx_status->tx_status_0,
+       ts->ts_longretry = AR5K_REG_MS(txstat0,
                AR5K_DESC_TX_STATUS0_LONG_RETRY_COUNT);
-       ts->ts_seqnum = AR5K_REG_MS(tx_status->tx_status_1,
+       ts->ts_seqnum = AR5K_REG_MS(txstat1,
                AR5K_DESC_TX_STATUS1_SEQ_NUM);
-       ts->ts_rssi = AR5K_REG_MS(tx_status->tx_status_1,
+       ts->ts_rssi = AR5K_REG_MS(txstat1,
                AR5K_DESC_TX_STATUS1_ACK_SIG_STRENGTH);
-       ts->ts_antenna = (tx_status->tx_status_1 &
+       ts->ts_antenna = (txstat1 &
                AR5K_DESC_TX_STATUS1_XMIT_ANTENNA_5212) ? 2 : 1;
        ts->ts_status = 0;
 
-       ts->ts_final_idx = AR5K_REG_MS(tx_status->tx_status_1,
+       ts->ts_final_idx = AR5K_REG_MS(txstat1,
                        AR5K_DESC_TX_STATUS1_FINAL_TS_IX_5212);
 
        /* The longretry counter has the number of un-acked retries
@@ -437,17 +443,17 @@ static int ath5k_hw_proc_4word_tx_status(struct ath5k_hw *ah,
        ts->ts_retry[ts->ts_final_idx] = ts->ts_longretry;
        switch (ts->ts_final_idx) {
        case 3:
-               ts->ts_retry[2] = AR5K_REG_MS(tx_ctl->tx_control_2,
+               ts->ts_retry[2] = AR5K_REG_MS(txctl2,
                        AR5K_4W_TX_DESC_CTL2_XMIT_TRIES2);
                ts->ts_longretry += ts->ts_retry[2];
                /* fall through */
        case 2:
-               ts->ts_retry[1] = AR5K_REG_MS(tx_ctl->tx_control_2,
+               ts->ts_retry[1] = AR5K_REG_MS(txctl2,
                        AR5K_4W_TX_DESC_CTL2_XMIT_TRIES1);
                ts->ts_longretry += ts->ts_retry[1];
                /* fall through */
        case 1:
-               ts->ts_retry[0] = AR5K_REG_MS(tx_ctl->tx_control_2,
+               ts->ts_retry[0] = AR5K_REG_MS(txctl2,
                        AR5K_4W_TX_DESC_CTL2_XMIT_TRIES1);
                ts->ts_longretry += ts->ts_retry[0];
                /* fall through */
@@ -456,15 +462,14 @@ static int ath5k_hw_proc_4word_tx_status(struct ath5k_hw *ah,
        }
 
        /* TX error */
-       if (!(tx_status->tx_status_0 & AR5K_DESC_TX_STATUS0_FRAME_XMIT_OK)) {
-               if (tx_status->tx_status_0 &
-                               AR5K_DESC_TX_STATUS0_EXCESSIVE_RETRIES)
+       if (!(txstat0 & AR5K_DESC_TX_STATUS0_FRAME_XMIT_OK)) {
+               if (txstat0 & AR5K_DESC_TX_STATUS0_EXCESSIVE_RETRIES)
                        ts->ts_status |= AR5K_TXERR_XRETRY;
 
-               if (tx_status->tx_status_0 & AR5K_DESC_TX_STATUS0_FIFO_UNDERRUN)
+               if (txstat0 & AR5K_DESC_TX_STATUS0_FIFO_UNDERRUN)
                        ts->ts_status |= AR5K_TXERR_FIFO;
 
-               if (tx_status->tx_status_0 & AR5K_DESC_TX_STATUS0_FILTERED)
+               if (txstat0 & AR5K_DESC_TX_STATUS0_FILTERED)
                        ts->ts_status |= AR5K_TXERR_FILT;
        }