Commit 2b396a12 authored by Johannes Berg's avatar Johannes Berg Committed by John W. Linville
Browse files

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: default avatarJohannes Berg <johannes@sipsolutions.net>
Signed-off-by: default avatarReinette Chatre <reinette.chatre@intel.com>
Signed-off-by: default avatarJohn W. Linville <linville@tuxdriver.com>
parent 9bddbab3

drivers/net/wireless/iwlwifi/iwl-core.c

+17 −13
Original line number Diff line number Diff line
@@ -948,8 +948,13 @@ EXPORT_SYMBOL(iwl_set_rxon_ht); 
#define IWL_NUM_IDLE_CHAINS_DUAL	2

#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.

 * 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;

}



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);



	/* # 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"

 * 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).

 */



	return is_cam ? active_cnt : IWL_NUM_IDLE_CHAINS_SINGLE;

static int iwl_get_idle_rx_chain_count(struct iwl_priv *priv, int active_cnt)

{

	return active_cnt;

}



/* up to 4 chains */

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