commit: d012d04e4d6312ea157b6cf19e9689af934f5aa7
From: Emmanuel Grumbach <[email protected]>
Date: Wed, 6 Jun 2012 13:55:02 +0200
Subject: iwlwifi: disable the buggy chain extension feature in HW

This feature has been reported to be buggy and enabled by
default. We therefore need to disable it manually.

Cc: [email protected]
Signed-off-by: Emmanuel Grumbach <[email protected]>
Signed-off-by: Johannes Berg <[email protected]>
Signed-off-by: John W. Linville <[email protected]>
---
 drivers/net/wireless/iwlwifi/iwl-prph.h       |    1 +
 drivers/net/wireless/iwlwifi/iwl-trans-pcie.c |    5 +++++
 2 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/drivers/net/wireless/iwlwifi/iwl-prph.h 
b/drivers/net/wireless/iwlwifi/iwl-prph.h
index 3b10692..dfd5466 100644
--- a/drivers/net/wireless/iwlwifi/iwl-prph.h
+++ b/drivers/net/wireless/iwlwifi/iwl-prph.h
@@ -224,6 +224,7 @@
 #define SCD_TXFACT             (SCD_BASE + 0x10)
 #define SCD_ACTIVE             (SCD_BASE + 0x14)
 #define SCD_QUEUECHAIN_SEL     (SCD_BASE + 0xe8)
+#define SCD_CHAINEXT_EN                (SCD_BASE + 0x244)
 #define SCD_AGGR_SEL           (SCD_BASE + 0x248)
 #define SCD_INTERRUPT_MASK     (SCD_BASE + 0x108)
 
diff --git a/drivers/net/wireless/iwlwifi/iwl-trans-pcie.c 
b/drivers/net/wireless/iwlwifi/iwl-trans-pcie.c
index ec6fb39..79c6b91 100644
--- a/drivers/net/wireless/iwlwifi/iwl-trans-pcie.c
+++ b/drivers/net/wireless/iwlwifi/iwl-trans-pcie.c
@@ -1058,6 +1058,11 @@ static void iwl_tx_start(struct iwl_trans *trans)
        iwl_write_prph(trans, SCD_DRAM_BASE_ADDR,
                       trans_pcie->scd_bc_tbls.dma >> 10);
 
+       /* The chain extension of the SCD doesn't work well. This feature is
+        * enabled by default by the HW, so we need to disable it manually.
+        */
+       iwl_write_prph(trans, SCD_CHAINEXT_EN, 0);
+
        /* Enable DMA channel */
        for (chan = 0; chan < FH_TCSR_CHNL_NUM ; chan++)
                iwl_write_direct32(trans, FH_TCSR_CHNL_TX_CONFIG_REG(chan),
-- 
1.7.3.4
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