iwlwifi: pcie: remove non-responsive device

If we fail to to grab NIC access because the device is not responding
(i.e. CSR_GP_CNTRL returns 0xFFFFFFFF), remove the device from the PCI
bus, to avoid any further damage, and to let the user space rescan.

In order to inform the userspace that a rescan is needed, we send a
kobject uevent with "INACCESSIBLE".

This functionality is disabled by default, but can be enabled via a
new module parameter called "remove_when_gone".  In the future we may
change this module parameter to include 3 modes instead: do nothing;
auto-rescan or; send uevent.
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Rajat Jain <rajatja@google.com>

drivers/net/wireless/intel/iwlwifi/iwl-drv.c

@@ -1850,3 +1850,9 @@ MODULE_PARM_DESC(d0i3_timeout, "Timeout to D0i3 entry when idle (ms)");
 
 module_param_named(disable_11ac, iwlwifi_mod_params.disable_11ac, bool, 0444);
 MODULE_PARM_DESC(disable_11ac, "Disable VHT capabilities (default: false)");
+
+module_param_named(remove_when_gone,
+		   iwlwifi_mod_params.remove_when_gone, bool,
+		   0444);
+MODULE_PARM_DESC(remove_when_gone,
+		 "Remove dev from PCIe bus if it is deemed inaccessible (default: false)");

drivers/net/wireless/intel/iwlwifi/iwl-modparams.h

@@ -122,6 +122,7 @@ enum iwl_uapsd_disable {
  * @lar_disable: disable LAR (regulatory), default = 0
  * @fw_monitor: allow to use firmware monitor
  * @disable_11ac: disable VHT capabilities, default = false.
+ * @remove_when_gone: remove an inaccessible device from the PCIe bus.
  */
 struct iwl_mod_params {
 	int swcrypto;
@@ -143,6 +144,7 @@ struct iwl_mod_params {
 	bool lar_disable;
 	bool fw_monitor;
 	bool disable_11ac;
+	bool remove_when_gone;
 };
 
 #endif /* #__iwl_modparams_h__ */

drivers/net/wireless/intel/iwlwifi/pcie/internal.h

@@ -383,6 +383,8 @@ struct iwl_self_init_dram {
  * @hw_init_mask: initial unmasked hw causes
  * @fh_mask: current unmasked fh causes
  * @hw_mask: current unmasked hw causes
+ * @in_rescan: true if we have triggered a device rescan
+ * @scheduled_for_removal: true if we have scheduled a device removal
  */
 struct iwl_trans_pcie {
 	struct iwl_rxq *rxq;
@@ -464,6 +466,9 @@ struct iwl_trans_pcie {
 	u32 fh_mask;
 	u32 hw_mask;
 	cpumask_t affinity_mask[IWL_MAX_RX_HW_QUEUES];
+	u16 tx_cmd_queue_size;
+	bool in_rescan;
+	bool scheduled_for_removal;
 };
 
 static inline struct iwl_trans_pcie *

drivers/net/wireless/intel/iwlwifi/pcie/trans.c

@@ -75,6 +75,7 @@
 #include <linux/gfp.h>
 #include <linux/vmalloc.h>
 #include <linux/pm_runtime.h>
+#include <linux/module.h>
 
 #include "iwl-drv.h"
 #include "iwl-trans.h"
@@ -1935,6 +1936,29 @@ static void iwl_trans_pcie_set_pmi(struct iwl_trans *trans, bool state)
 		clear_bit(STATUS_TPOWER_PMI, &trans->status);
 }
 
+struct iwl_trans_pcie_removal {
+	struct pci_dev *pdev;
+	struct work_struct work;
+};
+
+static void iwl_trans_pcie_removal_wk(struct work_struct *wk)
+{
+	struct iwl_trans_pcie_removal *removal =
+		container_of(wk, struct iwl_trans_pcie_removal, work);
+	struct pci_dev *pdev = removal->pdev;
+	char *prop[] = {"EVENT=INACCESSIBLE", NULL};
+
+	dev_err(&pdev->dev, "Device gone - attempting removal\n");
+	kobject_uevent_env(&pdev->dev.kobj, KOBJ_CHANGE, prop);
+	pci_lock_rescan_remove();
+	pci_dev_put(pdev);
+	pci_stop_and_remove_bus_device(pdev);
+	pci_unlock_rescan_remove();
+
+	kfree(removal);
+	module_put(THIS_MODULE);
+}
+
 static bool iwl_trans_pcie_grab_nic_access(struct iwl_trans *trans,
 					   unsigned long *flags)
 {
@@ -1977,11 +2001,55 @@ static bool iwl_trans_pcie_grab_nic_access(struct iwl_trans *trans,
 			   (BIT(trans->cfg->csr->flag_mac_clock_ready) |
 			    CSR_GP_CNTRL_REG_FLAG_GOING_TO_SLEEP), 15000);
 	if (unlikely(ret < 0)) {
-		iwl_trans_pcie_dump_regs(trans);
-		iwl_write32(trans, CSR_RESET, CSR_RESET_REG_FLAG_FORCE_NMI);
+		u32 cntrl = iwl_read32(trans, CSR_GP_CNTRL);
+
 		WARN_ONCE(1,
 			  "Timeout waiting for hardware access (CSR_GP_CNTRL 0x%08x)\n",
-			  iwl_read32(trans, CSR_GP_CNTRL));
+			  cntrl);
+
+		iwl_trans_pcie_dump_regs(trans);
+
+		if (iwlwifi_mod_params.remove_when_gone && cntrl == ~0U) {
+			struct iwl_trans_pcie_removal *removal;
+
+			if (trans_pcie->scheduled_for_removal)
+				goto err;
+
+			IWL_ERR(trans, "Device gone - scheduling removal!\n");
+
+			/*
+			 * get a module reference to avoid doing this
+			 * while unloading anyway and to avoid
+			 * scheduling a work with code that's being
+			 * removed.
+			 */
+			if (!try_module_get(THIS_MODULE)) {
+				IWL_ERR(trans,
+					"Module is being unloaded - abort\n");
+				goto err;
+			}
+
+			removal = kzalloc(sizeof(*removal), GFP_ATOMIC);
+			if (!removal) {
+				module_put(THIS_MODULE);
+				goto err;
+			}
+			/*
+			 * we don't need to clear this flag, because
+			 * the trans will be freed and reallocated.
+			*/
+			trans_pcie->scheduled_for_removal = true;
+
+			removal->pdev = to_pci_dev(trans->dev);
+			INIT_WORK(&removal->work, iwl_trans_pcie_removal_wk);
+			pci_dev_get(removal->pdev);
+			schedule_work(&removal->work);
+		} else {
+			iwl_write32(trans, CSR_RESET,
+				    CSR_RESET_REG_FLAG_FORCE_NMI);
+		}
+
+err:
 		spin_unlock_irqrestore(&trans_pcie->reg_lock, *flags);
 		return false;
 	}