[ 39/69] iwlwifi: disable the buggy chain extension feature in HW

[Ben Hutchings]

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Emmanuel Grumbach <emmanuel.grumbach@xxxxxxxxx>

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@xxxxxxxxx>
Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
Signed-off-by: John W. Linville <linville@xxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/net/wireless/iwlwifi/iwl-prph.h       |    1 +
 drivers/net/wireless/iwlwifi/iwl-trans-pcie.c |    5 +++++
 2 files changed, 6 insertions(+)

--- 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)
 
--- a/drivers/net/wireless/iwlwifi/iwl-trans-pcie.c
+++ b/drivers/net/wireless/iwlwifi/iwl-trans-pcie.c
@@ -868,6 +868,11 @@
 	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(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),


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