mac80211: enable spatial multiplexing powersave

Enable spatial multiplexing in mac80211 by telling the
driver what to do and, where necessary, sending action
frames to the AP to update the requested SMPS mode.

Also includes a trivial implementation for hwsim that
just logs the requested mode.

For now, the userspace interface is in debugfs only,
and let you toggle the requested mode at any time.

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

1 files changed, 59 insertions, 0 deletions

diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index e94cc526b0f6..e6b6bf81d5b9 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -597,8 +597,10 @@ enum ieee80211_conf_flags {
  * @IEEE80211_CONF_CHANGE_CHANNEL: the channel/channel_type changed
  * @IEEE80211_CONF_CHANGE_RETRY_LIMITS: retry limits changed
  * @IEEE80211_CONF_CHANGE_IDLE: Idle flag changed
+ * @IEEE80211_CONF_CHANGE_SMPS: Spatial multiplexing powersave mode changed
  */
 enum ieee80211_conf_changed {
+        IEEE80211_CONF_CHANGE_SMPS              = BIT(1),
         IEEE80211_CONF_CHANGE_LISTEN_INTERVAL   = BIT(2),
         IEEE80211_CONF_CHANGE_MONITOR           = BIT(3),
         IEEE80211_CONF_CHANGE_PS                = BIT(4),
@@ -609,6 +611,21 @@ enum ieee80211_conf_changed {
 };
 
 /**
+ * enum ieee80211_smps_mode - spatial multiplexing power save mode
+ *
+ * @
+ */
+enum ieee80211_smps_mode {
+        IEEE80211_SMPS_AUTOMATIC,
+        IEEE80211_SMPS_OFF,
+        IEEE80211_SMPS_STATIC,
+        IEEE80211_SMPS_DYNAMIC,
+
+        /* keep last */
+        IEEE80211_SMPS_NUM_MODES,
+};
+
+/**
  * struct ieee80211_conf - configuration of the device
  *
  * This struct indicates how the driver shall configure the hardware.
@@ -636,6 +653,10 @@ enum ieee80211_conf_changed {
  * @short_frame_max_tx_count: Maximum number of transmissions for a "short"
  *    frame, called "dot11ShortRetryLimit" in 802.11, but actually means the
  *    number of transmissions not the number of retries
+ *
+ * @smps_mode: spatial multiplexing powersave mode; note that
+ *      %IEEE80211_SMPS_STATIC is used when the device is not
+ *      configured for an HT channel
  */
 struct ieee80211_conf {
         u32 flags;
@@ -648,6 +669,7 @@ struct ieee80211_conf {
 
         struct ieee80211_channel *channel;
         enum nl80211_channel_type channel_type;
+        enum ieee80211_smps_mode smps_mode;
 };
 
 /**
@@ -930,6 +952,16 @@ enum ieee80211_tkip_key_type {
  * @IEEE80211_HW_BEACON_FILTER:
  *      Hardware supports dropping of irrelevant beacon frames to
  *      avoid waking up cpu.
+ *
+ * @IEEE80211_HW_SUPPORTS_STATIC_SMPS:
+ *      Hardware supports static spatial multiplexing powersave,
+ *      ie. can turn off all but one chain even on HT connections
+ *      that should be using more chains.
+ *
+ * @IEEE80211_HW_SUPPORTS_DYNAMIC_SMPS:
+ *      Hardware supports dynamic spatial multiplexing powersave,
+ *      ie. can turn off all but one chain and then wake the rest
+ *      up as required after, for example, rts/cts handshake.
  */
 enum ieee80211_hw_flags {
         IEEE80211_HW_HAS_RATE_CONTROL                   = 1<<0,
@@ -947,6 +979,8 @@ enum ieee80211_hw_flags {
         IEEE80211_HW_SUPPORTS_DYNAMIC_PS                = 1<<12,
         IEEE80211_HW_MFP_CAPABLE                        = 1<<13,
         IEEE80211_HW_BEACON_FILTER                      = 1<<14,
+        IEEE80211_HW_SUPPORTS_STATIC_SMPS               = 1<<15,
+        IEEE80211_HW_SUPPORTS_DYNAMIC_SMPS              = 1<<16,
 };
 
 /**
@@ -1215,6 +1249,31 @@ ieee80211_get_alt_retry_rate(const struct ieee80211_hw *hw,
  */
 
 /**
+ * DOC: Spatial multiplexing power save
+ *
+ * SMPS (Spatial multiplexing power save) is a mechanism to conserve
+ * power in an 802.11n implementation. For details on the mechanism
+ * and rationale, please refer to 802.11 (as amended by 802.11n-2009)
+ * "11.2.3 SM power save".
+ *
+ * The mac80211 implementation is capable of sending action frames
+ * to update the AP about the station's SMPS mode, and will instruct
+ * the driver to enter the specific mode. It will also announce the
+ * requested SMPS mode during the association handshake. Hardware
+ * support for this feature is required, and can be indicated by
+ * hardware flags.
+ *
+ * The default mode will be "automatic", which nl80211/cfg80211
+ * defines to be dynamic SMPS in (regular) powersave, and SMPS
+ * turned off otherwise.
+ *
+ * To support this feature, the driver must set the appropriate
+ * hardware support flags, and handle the SMPS flag to the config()
+ * operation. It will then with this mechanism be instructed to
+ * enter the requested SMPS mode while associated to an HT AP.
+ */
+
+/**
  * DOC: Frame filtering
  *
  * mac80211 requires to see many management frames for proper