iwlwifi: eliminate the possible 1/2 dBm tx power loss in 6x00 & 6x50 series

In both 6x00 and 6x50 series, the enhanced/extended tx power table in
EEPROM is used to set the max. tx power limit.
This new tx power table is in 1/2 dBm format, which creates an issue of
possibility of 1/2 dBm loss when driver set the tx power limit; because
of driver keep track and report the tx power in dBm format.

In order to prevent the 1/2 dBm loss, keep track of the true max tx
power in 1/2 dBm format in driver; do the comparison and adjust the tx
power if needed when send tx power command to uCode.

Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

3 files changed, 52 insertions, 14 deletions

diff --git a/drivers/net/wireless/iwlwifi/iwl-5000.c b/drivers/net/wireless/iwlwifi/iwl-5000.c
index 6eaf26b0763..48982fb4499 100644
--- a/drivers/net/wireless/iwlwifi/iwl-5000.c
+++ b/drivers/net/wireless/iwlwifi/iwl-5000.c
@@ -1250,6 +1250,22 @@ int  iwl5000_send_tx_power(struct iwl_priv *priv)
 
         /* half dBm need to multiply */
         tx_power_cmd.global_lmt = (s8)(2 * priv->tx_power_user_lmt);
+
+        if (priv->tx_power_lmt_in_half_dbm &&
+            priv->tx_power_lmt_in_half_dbm < tx_power_cmd.global_lmt) {
+                /*
+                 * For the newer devices which using enhanced/extend tx power
+                 * table in EEPROM, the format is in half dBm. driver need to
+                 * convert to dBm format before report to mac80211.
+                 * By doing so, there is a possibility of 1/2 dBm resolution
+                 * lost. driver will perform "round-up" operation before
+                 * reporting, but it will cause 1/2 dBm tx power over the
+                 * regulatory limit. Perform the checking here, if the
+                 * "tx_power_user_lmt" is higher than EEPROM value (in
+                 * half-dBm format), lower the tx power based on EEPROM
+                 */
+                tx_power_cmd.global_lmt = priv->tx_power_lmt_in_half_dbm;
+        }
         tx_power_cmd.flags = IWL50_TX_POWER_NO_CLOSED;
         tx_power_cmd.srv_chan_lmt = IWL50_TX_POWER_AUTO;
 
diff --git a/drivers/net/wireless/iwlwifi/iwl-dev.h b/drivers/net/wireless/iwlwifi/iwl-dev.h
index 774a315996e..a474383ec0b 100644
--- a/drivers/net/wireless/iwlwifi/iwl-dev.h
+++ b/drivers/net/wireless/iwlwifi/iwl-dev.h
@@ -1247,6 +1247,7 @@ struct iwl_priv {
         /* TX Power */
         s8 tx_power_user_lmt;
         s8 tx_power_device_lmt;
+        s8 tx_power_lmt_in_half_dbm; /* max tx power in half-dBm format */
 
 
 #ifdef CONFIG_IWLWIFI_DEBUG
diff --git a/drivers/net/wireless/iwlwifi/iwl-eeprom.c b/drivers/net/wireless/iwlwifi/iwl-eeprom.c
index e42eb6499f0..ac88ff042d4 100644
--- a/drivers/net/wireless/iwlwifi/iwl-eeprom.c
+++ b/drivers/net/wireless/iwlwifi/iwl-eeprom.c
@@ -762,7 +762,8 @@ static int iwl_mod_ht40_chan_info(struct iwl_priv *priv,
  *     find the highest tx power from all chains for the channel
  */
 static s8 iwl_get_max_txpower_avg(struct iwl_priv *priv,
-                struct iwl_eeprom_enhanced_txpwr *enhanced_txpower, int element)
+                struct iwl_eeprom_enhanced_txpwr *enhanced_txpower,
+                int element, s8 *max_txpower_in_half_dbm)
 {
         s8 max_txpower_avg = 0; /* (dBm) */
 
@@ -794,10 +795,14 @@ static s8 iwl_get_max_txpower_avg(struct iwl_priv *priv,
             (enhanced_txpower[element].mimo3_max > max_txpower_avg))
                 max_txpower_avg = enhanced_txpower[element].mimo3_max;
 
-        /* max. tx power in EEPROM is in 1/2 dBm format
-         * convert from 1/2 dBm to dBm
+        /*
+         * max. tx power in EEPROM is in 1/2 dBm format
+         * convert from 1/2 dBm to dBm (round-up convert)
+         * but we also do not want to loss 1/2 dBm resolution which
+         * will impact performance
          */
-        return max_txpower_avg >> 1;
+        *max_txpower_in_half_dbm = max_txpower_avg;
+        return (max_txpower_avg & 0x01) + (max_txpower_avg >> 1);
 }
 
 /**
@@ -806,7 +811,7 @@ static s8 iwl_get_max_txpower_avg(struct iwl_priv *priv,
  */
 static s8 iwl_update_common_txpower(struct iwl_priv *priv,
                 struct iwl_eeprom_enhanced_txpwr *enhanced_txpower,
-                int section, int element)
+                int section, int element, s8 *max_txpower_in_half_dbm)
 {
         struct iwl_channel_info *ch_info;
         int ch;
@@ -820,20 +825,22 @@ static s8 iwl_update_common_txpower(struct iwl_priv *priv,
         if (element == EEPROM_TXPOWER_COMMON_HT40_INDEX)
                 is_ht40 = true;
         max_txpower_avg =
-                iwl_get_max_txpower_avg(priv, enhanced_txpower, element);
+                iwl_get_max_txpower_avg(priv, enhanced_txpower,
+                                        element, max_txpower_in_half_dbm);
+
         ch_info = priv->channel_info;
 
         for (ch = 0; ch < priv->channel_count; ch++) {
                 /* find matching band and update tx power if needed */
                 if ((ch_info->band == enhinfo[section].band) &&
-                    (ch_info->max_power_avg < max_txpower_avg) && (!is_ht40)) {
+                    (ch_info->max_power_avg < max_txpower_avg) &&
+                    (!is_ht40)) {
                         /* Update regulatory-based run-time data */
                         ch_info->max_power_avg = ch_info->curr_txpow =
-                            max_txpower_avg;
+                                max_txpower_avg;
                         ch_info->scan_power = max_txpower_avg;
                 }
                 if ((ch_info->band == enhinfo[section].band) && is_ht40 &&
-                    ch_info->ht40_max_power_avg &&
                     (ch_info->ht40_max_power_avg < max_txpower_avg)) {
                         /* Update regulatory-based run-time data */
                         ch_info->ht40_max_power_avg = max_txpower_avg;
@@ -849,7 +856,7 @@ static s8 iwl_update_common_txpower(struct iwl_priv *priv,
  */
 static s8 iwl_update_channel_txpower(struct iwl_priv *priv,
                 struct iwl_eeprom_enhanced_txpwr *enhanced_txpower,
-                int section, int element)
+                int section, int element, s8 *max_txpower_in_half_dbm)
 {
         struct iwl_channel_info *ch_info;
         int ch;
@@ -858,7 +865,8 @@ static s8 iwl_update_channel_txpower(struct iwl_priv *priv,
 
         channel = enhinfo[section].iwl_eeprom_section_channel[element];
         max_txpower_avg =
-                iwl_get_max_txpower_avg(priv, enhanced_txpower, element);
+                iwl_get_max_txpower_avg(priv, enhanced_txpower,
+                                        element, max_txpower_in_half_dbm);
 
         ch_info = priv->channel_info;
         for (ch = 0; ch < priv->channel_count; ch++) {
@@ -872,7 +880,6 @@ static s8 iwl_update_channel_txpower(struct iwl_priv *priv,
                                 ch_info->scan_power = max_txpower_avg;
                         }
                         if ((enhinfo[section].is_ht40) &&
-                            (ch_info->ht40_max_power_avg) &&
                             (ch_info->ht40_max_power_avg < max_txpower_avg)) {
                                 /* Update regulatory-based run-time data */
                                 ch_info->ht40_max_power_avg = max_txpower_avg;
@@ -894,6 +901,7 @@ void iwlcore_eeprom_enhanced_txpower(struct iwl_priv *priv)
         struct iwl_eeprom_enhanced_txpwr *enhanced_txpower;
         u32 offset;
         s8 max_txpower_avg; /* (dBm) */
+        s8 max_txpower_in_half_dbm; /* (half-dBm) */
 
         /* Loop through all the sections
          * adjust bands and channel's max tx power
@@ -920,16 +928,29 @@ void iwlcore_eeprom_enhanced_txpower(struct iwl_priv *priv)
                         if (enhinfo[section].is_common)
                                 max_txpower_avg =
                                         iwl_update_common_txpower(priv,
-                                        enhanced_txpower, section, element);
+                                                enhanced_txpower, section,
+                                                element,
+                                                &max_txpower_in_half_dbm);
                         else
                                 max_txpower_avg =
                                         iwl_update_channel_txpower(priv,
-                                        enhanced_txpower, section, element);
+                                                enhanced_txpower, section,
+                                                element,
+                                                &max_txpower_in_half_dbm);
 
                         /* Update the tx_power_user_lmt to the highest power
                          * supported by any channel */
                         if (max_txpower_avg > priv->tx_power_user_lmt)
                                 priv->tx_power_user_lmt = max_txpower_avg;
+
+                        /*
+                         * Update the tx_power_lmt_in_half_dbm to
+                         * the highest power supported by any channel
+                         */
+                        if (max_txpower_in_half_dbm >
+                            priv->tx_power_lmt_in_half_dbm)
+                                priv->tx_power_lmt_in_half_dbm =
+                                        max_txpower_in_half_dbm;
                 }
         }
 }