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iwlwifi: default to using all chains 

When instructing the microcode to use just a single
chain when we have power saving enabled, we should
also tell the AP that we are doing SM powersave.
However, using a single chain doesn't actually have
any power saving advantage while idle -- measurements
show that the power consumption is no different when
using one vs. two or three chains.

Therefore, always instruct the microcode to use all
chains.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
This commit is contained in:
Johannes Berg 2009-09-25 14:24:25 -07:00 committed by John W. Linville
parent 9bddbab36d
commit 2b396a1209
1 changed files with 17 additions and 13 deletions
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30
drivers/net/wireless/iwlwifi/iwl-core.c
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@ -948,8 +948,13 @@ EXPORT_SYMBOL(iwl_set_rxon_ht);
#define IWL_NUM_IDLE_CHAINS_DUAL 2 #define IWL_NUM_IDLE_CHAINS_DUAL 2
#define IWL_NUM_IDLE_CHAINS_SINGLE 1 #define IWL_NUM_IDLE_CHAINS_SINGLE 1
/* Determine how many receiver/antenna chains to use. /*
* More provides better reception via diversity. Fewer saves power. * Determine how many receiver/antenna chains to use.
*
* More provides better reception via diversity. Fewer saves power
* at the expense of throughput, but only when not in powersave to
* start with.
*
* MIMO (dual stream) requires at least 2, but works better with 3. * MIMO (dual stream) requires at least 2, but works better with 3.
* This does not determine *which* chains to use, just how many. * This does not determine *which* chains to use, just how many.
*/ */
@ -962,19 +967,18 @@ static int iwl_get_active_rx_chain_count(struct iwl_priv *priv)
return IWL_NUM_RX_CHAINS_MULTIPLE; return IWL_NUM_RX_CHAINS_MULTIPLE;
} }
/*
* When we are in power saving, there's no difference between
* using multiple chains or just a single chain, but due to the
* lack of SM PS we lose a lot of throughput if we use just a
* single chain.
*
* Therefore, use the active count here (which will use multiple
* chains unless connected to a legacy AP).
*/
static int iwl_get_idle_rx_chain_count(struct iwl_priv *priv, int active_cnt) static int iwl_get_idle_rx_chain_count(struct iwl_priv *priv, int active_cnt)
{ {
bool is_cam = !test_bit(STATUS_POWER_PMI, &priv->status); return active_cnt;
/* # Rx chains when idling and maybe trying to save power */
/*
* XXX: this is incorrect!!
* we always indicate to the AP that
* our SM PS mode is "disabled"
*/
return is_cam ? active_cnt : IWL_NUM_IDLE_CHAINS_SINGLE;
} }
/* up to 4 chains */ /* up to 4 chains */