iwlwifi: workaround interrupt handling no some platforms

This patch adds workaround for an interrupt related hardware bug on
some platforms.  (Apparently these platforms boot-up w/ INTX_DISABLED
set. -- JWL)
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

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

@@ -2602,6 +2602,7 @@ static int iwl4965_mac_start(struct ieee80211_hw *hw)
 {
 	struct iwl_priv *priv = hw->priv;
 	int ret;
+	u16 pci_cmd;
 
 	IWL_DEBUG_MAC80211("enter\n");
 
@@ -2612,6 +2613,13 @@ static int iwl4965_mac_start(struct ieee80211_hw *hw)
 	pci_restore_state(priv->pci_dev);
 	pci_enable_msi(priv->pci_dev);
 
+	/* enable interrupts if needed: hw bug w/a */
+	pci_read_config_word(priv->pci_dev, PCI_COMMAND, &pci_cmd);
+	if (pci_cmd & PCI_COMMAND_INTX_DISABLE) {
+		pci_cmd &= ~PCI_COMMAND_INTX_DISABLE;
+		pci_write_config_word(priv->pci_dev, PCI_COMMAND, pci_cmd);
+	}
+
 	ret = request_irq(priv->pci_dev->irq, iwl4965_isr, IRQF_SHARED,
 			  DRV_NAME, priv);
 	if (ret) {