iwlwifi: debugFs to enable/disable HT40 support

Add debugfs file to enable/disable HT40(40MHz) channel support.
By default, 40MHz is supported if AP can support the function.

By echo "1" to "disable_ht40" file, iwlwifi driver will disable the
40MHz support and only allow 20MHz channel.

Because the information exchange happen during association time,
so enable/disable ht40 channel only can be performed when it is not
associated with AP.

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>

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

@@ -632,6 +632,10 @@ u8 iwl_is_fat_tx_allowed(struct iwl_priv *priv,
 		if (!sta_ht_inf->ht_supported)
 			return 0;
 	}
+#ifdef CONFIG_IWLWIFI_DEBUG
+	if (priv->disable_ht40)
+		return 0;
+#endif
 	return iwl_is_channel_extension(priv, priv->band,
 			le16_to_cpu(priv->staging_rxon.channel),
 			iwl_ht_conf->extension_chan_offset);

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

@@ -88,6 +88,7 @@ struct iwl_debugfs {
 #ifdef CONFIG_IWLWIFI_LEDS
 		struct dentry *file_led;
 #endif
+		struct dentry *file_disable_ht40;
 	} dbgfs_data_files;
 	struct dir_rf_files {
 		struct dentry *file_disable_sensitivity;

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

@@ -653,6 +653,49 @@ static ssize_t iwl_dbgfs_thermal_throttling_read(struct file *file,
 	return ret;
 }
 
+static ssize_t iwl_dbgfs_disable_ht40_write(struct file *file,
+					 const char __user *user_buf,
+					 size_t count, loff_t *ppos)
+{
+	struct iwl_priv *priv = file->private_data;
+	char buf[8];
+	int buf_size;
+	int ht40;
+
+	memset(buf, 0, sizeof(buf));
+	buf_size = min(count, sizeof(buf) -  1);
+	if (copy_from_user(buf, user_buf, buf_size))
+		return -EFAULT;
+	if (sscanf(buf, "%d", &ht40) != 1)
+		return -EFAULT;
+	if (!iwl_is_associated(priv))
+		priv->disable_ht40 = ht40 ? true : false;
+	else {
+		IWL_ERR(priv, "Sta associated with AP - "
+			"Change to 40MHz channel support is not allowed\n");
+		return -EINVAL;
+	}
+
+	return count;
+}
+
+static ssize_t iwl_dbgfs_disable_ht40_read(struct file *file,
+					 char __user *user_buf,
+					 size_t count, loff_t *ppos)
+{
+	struct iwl_priv *priv = (struct iwl_priv *)file->private_data;
+	char buf[100];
+	int pos = 0;
+	const size_t bufsz = sizeof(buf);
+	ssize_t ret;
+
+	pos += scnprintf(buf + pos, bufsz - pos,
+			"11n 40MHz Mode: %s\n",
+			priv->disable_ht40 ? "Disabled" : "Enabled");
+	ret = simple_read_from_buffer(user_buf, count, ppos, buf, pos);
+	return ret;
+}
+
 DEBUGFS_READ_WRITE_FILE_OPS(sram);
 DEBUGFS_WRITE_FILE_OPS(log_event);
 DEBUGFS_READ_FILE_OPS(nvm);
@@ -667,6 +710,7 @@ DEBUGFS_READ_FILE_OPS(qos);
 DEBUGFS_READ_FILE_OPS(led);
 #endif
 DEBUGFS_READ_FILE_OPS(thermal_throttling);
+DEBUGFS_READ_WRITE_FILE_OPS(disable_ht40);
 
 /*
  * Create the debugfs files and directories
@@ -708,6 +752,7 @@ int iwl_dbgfs_register(struct iwl_priv *priv, const char *name)
 	DEBUGFS_ADD_FILE(led, data);
 #endif
 	DEBUGFS_ADD_FILE(thermal_throttling, data);
+	DEBUGFS_ADD_FILE(disable_ht40, data);
 	DEBUGFS_ADD_BOOL(disable_sensitivity, rf, &priv->disable_sens_cal);
 	DEBUGFS_ADD_BOOL(disable_chain_noise, rf,
 			 &priv->disable_chain_noise_cal);
@@ -747,6 +792,7 @@ void iwl_dbgfs_unregister(struct iwl_priv *priv)
 	DEBUGFS_REMOVE(priv->dbgfs->dbgfs_data_files.file_led);
 #endif
 	DEBUGFS_REMOVE(priv->dbgfs->dbgfs_data_files.file_thermal_throttling);
+	DEBUGFS_REMOVE(priv->dbgfs->dbgfs_data_files.file_disable_ht40);
 	DEBUGFS_REMOVE(priv->dbgfs->dir_data);
 	DEBUGFS_REMOVE(priv->dbgfs->dbgfs_rf_files.file_disable_sensitivity);
 	DEBUGFS_REMOVE(priv->dbgfs->dbgfs_rf_files.file_disable_chain_noise);

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

@@ -1164,6 +1164,7 @@ struct iwl_priv {
 	/* debugging info */
 	u32 framecnt_to_us;
 	atomic_t restrict_refcnt;
+	bool disable_ht40;
 #ifdef CONFIG_IWLWIFI_DEBUGFS
 	/* debugfs */
 	struct iwl_debugfs *dbgfs;