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From: Adrian Chadd <adrian@FreeBSD.org>
Date: Sun, 2 Oct 2011 13:51:26 +0000 (UTC)
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Subject: svn commit: r225924 - head/sys/dev/ath/ath_hal/ar5416
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Author: adrian
Date: Sun Oct  2 13:51:26 2011
New Revision: 225924
URL: http://svn.freebsd.org/changeset/base/225924

Log:
  Document exactly what the RX interrupt mitigation timers do.

Modified:
  head/sys/dev/ath/ath_hal/ar5416/ar5416_reset.c

Modified: head/sys/dev/ath/ath_hal/ar5416/ar5416_reset.c
==============================================================================
--- head/sys/dev/ath/ath_hal/ar5416/ar5416_reset.c	Sun Oct  2 13:48:15 2011	(r225923)
+++ head/sys/dev/ath/ath_hal/ar5416/ar5416_reset.c	Sun Oct  2 13:51:26 2011	(r225924)
@@ -358,8 +358,30 @@ ar5416Reset(struct ath_hal *ah, HAL_OPMO
 	OS_REG_WRITE(ah, AR_OBS, 8);
 
 #ifdef	AH_AR5416_INTERRUPT_MITIGATION
+	/*
+	 * Disable the "general" TX/RX mitigation timers.
+	 */
 	OS_REG_WRITE(ah, AR_MIRT, 0);
 
+	/*
+	 * This initialises the RX interrupt mitigation timers.
+	 *
+	 * The mitigation timers begin at idle and are triggered
+	 * upon the RXOK of a single frame (or sub-frame, for A-MPDU.)
+	 * Then, the RX mitigation interrupt will fire:
+	 *
+	 * + 250uS after the last RX'ed frame, or
+	 * + 700uS after the first RX'ed frame
+	 *
+	 * Thus, the LAST field dictates the extra latency
+	 * induced by the RX mitigation method and the FIRST
+	 * field dictates how long to delay before firing an
+	 * RX mitigation interrupt.
+	 *
+	 * Please note this only seems to be for RXOK frames;
+	 * not CRC or PHY error frames.
+	 *
+	 */
 	OS_REG_RMW_FIELD(ah, AR_RIMT, AR_RIMT_LAST, 250);
 	OS_REG_RMW_FIELD(ah, AR_RIMT, AR_RIMT_FIRST, 700);
 #endif