iwlwifi: don't disable SCD chain extension on newer devices

7000 device series have a fix for this hardware feature.
Stop disabling it, and get an improvement in Tx throughput.
This feature allows the scheduler to fetch more frames on
the fly while an A-MPDU is being built - which means that
we can get larger A-MPDU. This, of course, give an
improvement in the Tx throughput.
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>

drivers/net/wireless/iwlwifi/iwl-1000.c

@@ -62,6 +62,7 @@ static const struct iwl_base_params iwl1000_base_params = {
 	.led_compensation = 51,
 	.wd_timeout = IWL_WATCHDOG_DISABLED,
 	.max_event_log_size = 128,
+	.scd_chain_ext_wa = true,
 };
 
 static const struct iwl_ht_params iwl1000_ht_params = {

drivers/net/wireless/iwlwifi/iwl-2000.c

@@ -75,6 +75,7 @@ static const struct iwl_base_params iwl2000_base_params = {
 	.wd_timeout = IWL_DEF_WD_TIMEOUT,
 	.max_event_log_size = 512,
 	.shadow_reg_enable = false, /* TODO: fix bugs using this feature */
+	.scd_chain_ext_wa = true,
 };
 
 
@@ -88,6 +89,7 @@ static const struct iwl_base_params iwl2030_base_params = {
 	.wd_timeout = IWL_LONG_WD_TIMEOUT,
 	.max_event_log_size = 512,
 	.shadow_reg_enable = false, /* TODO: fix bugs using this feature */
+	.scd_chain_ext_wa = true,
 };
 
 static const struct iwl_ht_params iwl2000_ht_params = {

drivers/net/wireless/iwlwifi/iwl-5000.c

@@ -61,6 +61,7 @@ static const struct iwl_base_params iwl5000_base_params = {
 	.led_compensation = 51,
 	.wd_timeout = IWL_WATCHDOG_DISABLED,
 	.max_event_log_size = 512,
+	.scd_chain_ext_wa = true,
 };
 
 static const struct iwl_ht_params iwl5000_ht_params = {

drivers/net/wireless/iwlwifi/iwl-6000.c

@@ -85,6 +85,7 @@ static const struct iwl_base_params iwl6000_base_params = {
 	.wd_timeout = IWL_DEF_WD_TIMEOUT,
 	.max_event_log_size = 512,
 	.shadow_reg_enable = false, /* TODO: fix bugs using this feature */
+	.scd_chain_ext_wa = true,
 };
 
 static const struct iwl_base_params iwl6050_base_params = {
@@ -97,6 +98,7 @@ static const struct iwl_base_params iwl6050_base_params = {
 	.wd_timeout = IWL_DEF_WD_TIMEOUT,
 	.max_event_log_size = 1024,
 	.shadow_reg_enable = false, /* TODO: fix bugs using this feature */
+	.scd_chain_ext_wa = true,
 };
 
 static const struct iwl_base_params iwl6000_g2_base_params = {
@@ -109,6 +111,7 @@ static const struct iwl_base_params iwl6000_g2_base_params = {
 	.wd_timeout = IWL_LONG_WD_TIMEOUT,
 	.max_event_log_size = 512,
 	.shadow_reg_enable = false, /* TODO: fix bugs using this feature */
+	.scd_chain_ext_wa = true,
 };
 
 static const struct iwl_ht_params iwl6000_ht_params = {

drivers/net/wireless/iwlwifi/iwl-config.h

@@ -148,6 +148,7 @@ static inline u8 num_of_ant(u8 mask)
  * @shadow_reg_enable: HW shadow register support
  * @apmg_wake_up_wa: should the MAC access REQ be asserted when a command
  *	is in flight. This is due to a HW bug in 7260, 3160 and 7265.
+ * @scd_chain_ext_wa: should the chain extension feature in SCD be disabled.
  */
 struct iwl_base_params {
 	int eeprom_size;
@@ -163,6 +164,7 @@ struct iwl_base_params {
 	const bool shadow_reg_enable;
 	const bool pcie_l1_allowed;
 	const bool apmg_wake_up_wa;
+	const bool scd_chain_ext_wa;
 };
 
 /*

drivers/net/wireless/iwlwifi/pcie/tx.c

@@ -696,7 +696,8 @@ void iwl_pcie_tx_start(struct iwl_trans *trans, u32 scd_base_addr)
 	/* 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);
+	if (trans->cfg->base_params->scd_chain_ext_wa)
+		iwl_write_prph(trans, SCD_CHAINEXT_EN, 0);
 
 	iwl_trans_ac_txq_enable(trans, trans_pcie->cmd_queue,
 				trans_pcie->cmd_fifo);