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mt76: fix beacon timer drift

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The beacon timer drifts by 1 microsecond every TBTT. After 20 minutes
with a beacon interval of 100, the drift will be almost 12 ms, enough to
cause weird issues for devices in powersave mode.

Since the beacon timer is configured in units of 1/16 TU (64 us), we
need to adjust it once every 64 beacons and only for one beacon.

Signed-off-by: Felix Fietkau <[email protected]>
This commit is contained in:
Felix Fietkau
2018-05-18 17:46:01 +02:00
parent 73edb22822
commit 0b8d1ddec9
3 changed files with 41 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files
mt76x2.h
+4 -1
View File
@@ -120,10 +120,13 @@ struct mt76x2_dev {
u8 beacon_mask;
u8 beacon_data_mask;
u32 rxfilter;
u8 tbtt_count;
u16 beacon_int;
u16 chainmask;
u32 rxfilter;
struct mt76x2_calibration cal;
s8 target_power;
mt76x2_main.c
+4 -1
View File
@@ -231,10 +231,13 @@ mt76x2_bss_info_changed(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
if (changed & BSS_CHANGED_BSSID)
mt76x2_mac_set_bssid(dev, mvif->idx, info->bssid);
if (changed & BSS_CHANGED_BEACON_INT)
if (changed & BSS_CHANGED_BEACON_INT) {
mt76_rmw_field(dev, MT_BEACON_TIME_CFG,
MT_BEACON_TIME_CFG_INTVAL,
info->beacon_int << 4);
dev->beacon_int = info->beacon_int;
dev->tbtt_count = 0;
}
if (changed & BSS_CHANGED_BEACON_ENABLED) {
tasklet_disable(&dev->pre_tbtt_tasklet);
mt76x2_tx.c
+33
View File
@@ -218,6 +218,37 @@ mt76x2_add_buffered_bc(void *priv, u8 *mac, struct ieee80211_vif *vif)
data->tail[mvif->idx] = skb;
}
static void
mt76x2_resync_beacon_timer(struct mt76x2_dev *dev)
{
u32 timer_val = dev->beacon_int << 4;
dev->tbtt_count++;
/*
* Beacon timer drifts by 1us every tick, the timer is configured
* in 1/16 TU (64us) units.
*/
if (dev->tbtt_count < 62)
return;
if (dev->tbtt_count >= 64) {
dev->tbtt_count = 0;
return;
}
/*
* The updated beacon interval takes effect after two TBTT, because
* at this point the original interval has already been loaded into
* the next TBTT_TIMER value
*/
if (dev->tbtt_count == 62)
timer_val -= 1;
mt76_rmw_field(dev, MT_BEACON_TIME_CFG,
MT_BEACON_TIME_CFG_INTVAL, timer_val);
}
void mt76x2_pre_tbtt_tasklet(unsigned long arg)
{
struct mt76x2_dev *dev = (struct mt76x2_dev *) arg;
@@ -226,6 +257,8 @@ void mt76x2_pre_tbtt_tasklet(unsigned long arg)
struct sk_buff *skb;
int i, nframes;
mt76x2_resync_beacon_timer(dev);
data.dev = dev;
__skb_queue_head_init(&data.q);