iwlwifi: disable the buggy chain extension feature in HW

commit d012d04e4d6312ea157b6cf19e9689af934f5aa7 upstream.

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

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
[bwh: Backported to 3.2 as instructed: pass bus(trans) to iwl_write_prph()]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/net/wireless/iwlwifi/iwl-prph.h b/drivers/net/wireless/iwlwifi/iwl-prph.h
index d9b089e..0683006 100644 (file)
--- a/drivers/net/wireless/iwlwifi/iwl-prph.h
+++ b/drivers/net/wireless/iwlwifi/iwl-prph.h
@@ -228,6 +228,7 @@
 #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 5f17ab8..5815cf5 100644 (file)
--- a/drivers/net/wireless/iwlwifi/iwl-trans-pcie.c
+++ b/drivers/net/wireless/iwlwifi/iwl-trans-pcie.c
@@ -868,6 +868,11 @@ static void iwl_trans_pcie_tx_start(struct iwl_trans *trans)
        iwl_write_prph(bus(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(bus(trans), SCD_CHAINEXT_EN, 0);
+
        /* Enable DMA channel */
        for (chan = 0; chan < FH_TCSR_CHNL_NUM ; chan++)
                iwl_write_direct32(bus(trans), FH_TCSR_CHNL_TX_CONFIG_REG(chan),