mac80211: async station powersave handling

Some devices require that all frames to a station
are flushed when that station goes into powersave
mode before being able to send frames to that
station again when it wakes up or polls -- all in
order to avoid reordering and too many or too few
frames being sent to the station when it polls.

Normally, this is the case unless the station
goes to sleep and wakes up very quickly again.
But in that case, frames for it may be pending
on the hardware queues, and thus races could
happen in the case of multiple hardware queues
used for QoS/WMM. Normally this isn't a problem,
but with the iwlwifi mechanism we need to make
sure the race doesn't happen.

This makes mac80211 able to cope with the race
with driver help by a new WLAN_STA_PS_DRIVER
per-station flag that can be controlled by the
driver and tells mac80211 whether it can transmit
frames or not. This flag must be set according to
very specific rules outlined in the documentation
for the function that controls it.

When we buffer new frames for the station, we
normally set the TIM bit right away, but while
the driver has blocked transmission to that sta
we need to avoid that as well since we cannot
respond to the station if it wakes up due to the
TIM bit. Once the driver unblocks, we can set
the TIM bit.

Similarly, when the station just wakes up, we
need to wait until all other frames are flushed
before we can transmit frames to that station,
so the same applies here, we need to wait for
the driver to give the OK.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 20 insertions, 3 deletions

diff --git a/net/mac80211/sta_info.h b/net/mac80211/sta_info.h
index 703f5492ee65..4673454176ed 100644
--- a/net/mac80211/sta_info.h
+++ b/net/mac80211/sta_info.h
@@ -12,6 +12,7 @@
 #include <linux/list.h>
 #include <linux/types.h>
 #include <linux/if_ether.h>
+#include <linux/workqueue.h>
 #include "key.h"
 
 /**
@@ -21,7 +22,7 @@
  *
  * @WLAN_STA_AUTH: Station is authenticated.
  * @WLAN_STA_ASSOC: Station is associated.
- * @WLAN_STA_PS: Station is in power-save mode
+ * @WLAN_STA_PS_STA: Station is in power-save mode
  * @WLAN_STA_AUTHORIZED: Station is authorized to send/receive traffic.
  *      This bit is always checked so needs to be enabled for all stations
  *      when virtual port control is not in use.
@@ -36,11 +37,16 @@
  * @WLAN_STA_MFP: Management frame protection is used with this STA.
  * @WLAN_STA_SUSPEND: Set/cleared during a suspend/resume cycle.
  *      Used to deny ADDBA requests (both TX and RX).
+ * @WLAN_STA_PS_DRIVER: driver requires keeping this station in
+ *      power-save mode logically to flush frames that might still
+ *      be in the queues
+ * @WLAN_STA_PSPOLL: Station sent PS-poll while driver was keeping
+ *      station in power-save mode, reply when the driver unblocks.
  */
 enum ieee80211_sta_info_flags {
         WLAN_STA_AUTH           = 1<<0,
         WLAN_STA_ASSOC          = 1<<1,
-        WLAN_STA_PS             = 1<<2,
+        WLAN_STA_PS_STA         = 1<<2,
         WLAN_STA_AUTHORIZED     = 1<<3,
         WLAN_STA_SHORT_PREAMBLE = 1<<4,
         WLAN_STA_ASSOC_AP       = 1<<5,
@@ -48,7 +54,9 @@ enum ieee80211_sta_info_flags {
         WLAN_STA_WDS            = 1<<7,
         WLAN_STA_CLEAR_PS_FILT  = 1<<9,
         WLAN_STA_MFP            = 1<<10,
-        WLAN_STA_SUSPEND        = 1<<11
+        WLAN_STA_SUSPEND        = 1<<11,
+        WLAN_STA_PS_DRIVER      = 1<<12,
+        WLAN_STA_PSPOLL         = 1<<13,
 };
 
 #define STA_TID_NUM 16
@@ -216,6 +224,8 @@ struct sta_ampdu_mlme {
  * @plink_timer_was_running: used by suspend/resume to restore timers
  * @debugfs: debug filesystem info
  * @sta: station information we share with the driver
+ * @dead: set to true when sta is unlinked
+ * @drv_unblock_wk used for driver PS unblocking
  */
 struct sta_info {
         /* General information, mostly static */
@@ -229,8 +239,12 @@ struct sta_info {
         spinlock_t lock;
         spinlock_t flaglock;
 
+        struct work_struct drv_unblock_wk;
+
         u16 listen_interval;
 
+        bool dead;
+
         /*
          * for use by the internal lifetime management,
          * see __sta_info_unlink
@@ -430,4 +444,7 @@ int sta_info_flush(struct ieee80211_local *local,
 void ieee80211_sta_expire(struct ieee80211_sub_if_data *sdata,
                           unsigned long exp_time);
 
+void ieee80211_sta_ps_deliver_wakeup(struct sta_info *sta);
+void ieee80211_sta_ps_deliver_poll_response(struct sta_info *sta);
+
 #endif /* STA_INFO_H */