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 d9b089e9a1a182c1688bd906cb4dc9279e6af0a6..0683006ec68d8b6f747c1b8a562b8e4301570492 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 5f17ab8e76bacbc7e4521951c15a716a532afc45..5815cf5df2e8f5acbacb85d46700abe3ed9a5785 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),