ath5k: improve comments for optimized tx descriptor setup

Comment the use of local variables to reduce the number of load/store
operations on uncached memory, in hopes of not losing this optimization
accidentally in the future.

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

1 files changed, 6 insertions, 1 deletions

diff --git a/drivers/net/wireless/ath/ath5k/desc.c b/drivers/net/wireless/ath/ath5k/desc.c
index 0391813befd1..dd7cd95c364a 100644
--- a/drivers/net/wireless/ath/ath5k/desc.c
+++ b/drivers/net/wireless/ath/ath5k/desc.c
@@ -184,6 +184,11 @@ static int ath5k_hw_setup_4word_tx_desc(struct ath5k_hw *ah,
 {
         struct ath5k_hw_4w_tx_ctl *tx_ctl;
         unsigned int frame_len;
+
+        /*
+         * Use local variables for these to reduce load/store access on
+         * uncached memory
+         */
         u32 txctl0 = 0, txctl1 = 0, txctl2 = 0, txctl3 = 0;
 
         tx_ctl = &desc->ud.ds_tx5212.tx_ctl;
@@ -209,7 +214,7 @@ static int ath5k_hw_setup_4word_tx_desc(struct ath5k_hw *ah,
         if (tx_power > AR5K_TUNE_MAX_TXPOWER)
                 tx_power = AR5K_TUNE_MAX_TXPOWER;
 
-        /* Clear descriptor */
+        /* Clear descriptor status area */
         memset(&desc->ud.ds_tx5212.tx_stat, 0,
                sizeof(desc->ud.ds_tx5212.tx_stat));