Add troubleshooting for wireless on suspend/resume

Based on my own experiences reinventing the wheel.

doc.md

@@ -187,6 +187,7 @@ Troubleshooting
  * [Apple MacBook Troubleshooting](/doc/macbook-troubleshooting/)
  * [Getting Sony Vaio Z laptop to work with Qubes](/doc/sony-vaio-tinkering/)
  * [Troubleshooting UEFI related problems](/doc/uefi-troubleshooting/)
+ * [Fixing wireless on suspend & resume](/doc/wireless-troubleshooting/)
 
 
 Reference Pages

troubleshooting/wireless-troubleshooting.md

@@ -0,0 +1,121 @@
+---
+layout: doc
+title: Wireless Troubleshooting
+permalink: /doc/wireless-troubleshooting/
+redirect_from:
+- /en/doc/wireless-troubleshooting/
+---
+
+Wireless Troubleshooting Guide
+==============================
+
+These instructions may help with suspend/resume issues for more devices than just wireless cards, that is just the (unfortunately not uncommon) example used here.
+
+Resetting wireless cards by reloading drivers
+---------------------------------------------
+
+If your wireless card works, but after suspending and resuming your computer, the Network-Manager applet just says "Device not ready", then try un-loading and re-loading the driver.
+
+### Determining your wireless card driver ###
+
+First, determine which kernel module corresponds to your wireless card. There are several ways to do this.
+
+The easiest is via the output of `lspci -k` in your sys-net VM:
+
+~~~
+[user@sys-net ~]$ lspci -k
+00:00.0 Network controller: Intel Corporation Wireless 8260 (rev 3a)
+	Subsystem: Intel Corporation Device 0130
+	Kernel driver in use: iwlwifi
+	Kernel modules: iwlwifi
+~~~
+
+Here we see that the machine in question has an Intel wireless card, being used by the `iwlwifi` kernel module.
+
+
+### Checking logs for relevant messages ###
+
+View the output of `dmesg` in sys-net, and check if you see a bunch of wireless related errors. Depending on your hardware, they may look like the following (or not):
+
+~~~
+iwlwifi 0000:00:00.0: loaded firmware version 16.242414.0 op_mode iwlmvm
+iwlwifi 0000:00:00.0: Detected Intel(R) Dual Band Wireless AC 8260, REV=0x208
+...
+IPv6: ADDRCONF(NETDEV_UP): wlp0s0: link is not ready
+iwlwifi 0000:00:00.0: L1 Enabled - LTR Enabled
+iwlwifi 0000:00:00.0: L1 Enabled - LTR Enabled
+iwlwifi 0000:00:00.0: Failed to load firmware chunk!
+iwlwifi 0000:00:00.0: Could not load the [0] uCode section
+iwlwifi 0000:00:00.0: Failed to start INIT ucode: -110
+iwlwifi 0000:00:00.0: Failed to run INIT ucode: -110
+...
+iwlwifi 0000:00:00.0: Direct firmware load for iwlwifi-8000C-18.ucode failed with error -2
+~~~
+
+### Seeing what modules you have loaded ###
+
+You can check which drivers are currently loaded with `lsmod`, and view details about a module with `modinfo <module_name>`.
+
+For example, we list what modules we have loaded:
+
+~~~
+[user@sys-net ~]$ lsmod
+Module                  Size  Used by
+iwlmvm                315392  0
+iwlwifi               155648  1 iwlmvm
+mac80211              708608  1 iwlmvm
+cfg80211              557056  3 iwlwifi,mac80211,iwlmvm
+...
+~~~
+
+and check one:
+
+~~~
+[user@sys-net ~]$ modinfo iwlmvm | grep -E '^(description|author|depends):'
+author:         Copyright(c) 2003- 2015 Intel Corporation <ilw@linux.intel.com>
+description:    The new Intel(R) wireless AGN driver for Linux
+depends:        iwlwifi,mac80211,cfg80211
+~~~
+
+Hey, it's our wireless driver!
+
+Now, check if reloading the module makes wireless work again:
+
+~~~
+[user@sys-net ~]$ sudo rmmod iwlmvm
+[user@sys-net ~]$ sudo modprobe iwlmvm
+~~~
+
+and try reconnecting to a network that is known to work.
+
+If that is successful, see below about having Qubes automatically reload the driver for you. If not, try also reloading some dependent modules, in our example we must also reload iwlwifi:
+
+~~~
+[user@sys-net ~]$ modinfo iwlwifi | grep -E '^(description|author|depends):'
+author:         Copyright(c) 2003- 2015 Intel Corporation <ilw@linux.intel.com>
+description:    Intel(R) Wireless WiFi driver for Linux
+depends:        cfg80211
+~~~
+
+~~~
+[user@sys-net ~]$ sudo rmmod iwlmvm
+[user@sys-net ~]$ sudo rmmod iwlwifi
+[user@sys-net ~]$ sudo modprobe iwlwifi # note the reverse order of loading/unloading
+[user@sys-net ~]$ sudo modprobe iwlmvm
+~~~
+
+Automatically reloading drivers on suspend/resume
+-------------------------------------------------
+
+If reloading the driver (which resets the hardware into a known-state) resolves your issue when done manually, you can have Qubes automatically un/reload them on suspend & resume by listing the relevant modules in `/rw/config/suspend-module-blacklist`.
+
+In the above example, it would look like this:
+
+~~~
+[user@sys-net config]$ cat /rw/config/suspend-module-blacklist
+# You can list here modules you want to be unloaded before going to sleep. This
+# file is used only if the VM has any PCI device assigned. Modules will be
+# automatically loaded after resume.
+iwlmvm
+iwlwifi
+~~~