Author: adrian
Date: Thu Feb 21 08:42:40 2013
New Revision: 247092
URL: http://svnweb.freebsd.org/changeset/base/247092
Log:
Be slightly more paranoid with the TX DMA buffer maximum threshold.
Specifically - never jack the TX FIFO threshold up to the absolute
maximum; always leave enough space for two DMA transactions to
appear.
This is a paranoia from the Linux ath9k driver. It can't hurt.
Obtained from: Linux ath9k
Modified:
head/sys/dev/ath/ath_hal/ar5416/ar5416_attach.c
head/sys/dev/ath/ath_hal/ar5416/ar5416_reset.c
Modified: head/sys/dev/ath/ath_hal/ar5416/ar5416_attach.c
==============================================================================
--- head/sys/dev/ath/ath_hal/ar5416/ar5416_attach.c Thu Feb 21 08:21:14
2013 (r247091)
+++ head/sys/dev/ath/ath_hal/ar5416/ar5416_attach.c Thu Feb 21 08:42:40
2013 (r247092)
@@ -244,9 +244,23 @@ ar5416InitState(struct ath_hal_5416 *ahp
/* Set overridable ANI methods */
AH5212(ah)->ah_aniControl = ar5416AniControl;
- /* Default FIFO Trigger levels */
+ /*
+ * Default FIFO Trigger levels
+ *
+ * These define how filled the TX FIFO needs to be before
+ * the baseband begins to be given some data.
+ *
+ * To be paranoid, we ensure that the TX trigger level always
+ * has at least enough space for two TX DMA to occur.
+ * The TX DMA size is currently hard-coded to AR_TXCFG_DMASZ_128B.
+ * That means we need to leave at least 256 bytes available in
+ * the TX DMA FIFO.
+ */
#define AR_FTRIG_512B 0x00000080 // 5 bits total
- /* AR9285/AR9271 need to use half the TX FIFOs */
+ /*
+ * AR9285/AR9271 have half the size TX FIFO compared to
+ * other devices
+ */
if (AR_SREV_KITE(ah) || AR_SREV_9271(ah)) {
AH5212(ah)->ah_txTrigLev = (AR_FTRIG_256B >> AR_FTRIG_S);
AH5212(ah)->ah_maxTxTrigLev = ((2048 / 64) - 1);
@@ -255,6 +269,9 @@ ar5416InitState(struct ath_hal_5416 *ahp
AH5212(ah)->ah_maxTxTrigLev = ((4096 / 64) - 1);
}
#undef AR_FTRIG_512B
+
+ /* And now leave some headspace - 256 bytes */
+ AH5212(ah)->ah_maxTxTrigLev -= 4;
}
uint32_t
Modified: head/sys/dev/ath/ath_hal/ar5416/ar5416_reset.c
==============================================================================
--- head/sys/dev/ath/ath_hal/ar5416/ar5416_reset.c Thu Feb 21 08:21:14
2013 (r247091)
+++ head/sys/dev/ath/ath_hal/ar5416/ar5416_reset.c Thu Feb 21 08:42:40
2013 (r247092)
@@ -570,6 +570,10 @@ ar5416InitDMA(struct ath_hal *ah)
/*
* let mac dma writes be in 128 byte chunks
*/
+ /*
+ * XXX If you change this, you must change the headroom
+ * assigned in ah_maxTxTrigLev - see ar5416InitState().
+ */
OS_REG_WRITE(ah, AR_RXCFG,
(OS_REG_READ(ah, AR_RXCFG) & ~AR_RXCFG_DMASZ_MASK) |
AR_RXCFG_DMASZ_128B);
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