[PATCH AUTOSEL 4.19 028/146] iwlwifi: mvm: clear HW_RESTART_REQUESTED when stopping the interface

From: Sasha Levin
Date: Wed Oct 31 2018 - 19:52:51 EST

From: Emmanuel Grumbach <emmanuel.grumbach@xxxxxxxxx>

[ Upstream commit 155f7e0441cd121b1e673d465a35e99f4b9b2f0b ]

Fix a bug that happens in the following scenario:
1) suspend without WoWLAN
2) mac80211 calls drv_stop because of the suspend
3) __iwl_mvm_mac_stop deallocates the aux station
4) during drv_stop the firmware crashes
5) iwlmvm:
* asks mac80211 to kick the restart flow
6) mac80211 puts the restart worker into a freezable
queue which means that the worker will not run for now
since the workqueue is already frozen
7) ...
8) resume
9) mac80211 runs ieee80211_reconfig as part of the resume
10) mac80211 detects that a restart flow has been requested
and that we are now resuming from suspend and cancels
the restart worker
11) mac80211 calls drv_start()
12) __iwl_mvm_mac_start checks that IWL_MVM_STATUS_HW_RESTART_REQUESTED
clears it, sets IWL_MVM_STATUS_IN_HW_RESTART and calls
13) iwl_fw_error_dump gets called and accesses the device
to get debug data
14) iwl_mvm_up adds the aux station
15) iwl_mvm_add_aux_sta() allocates an internal station for
the aux station
16) iwl_mvm_allocate_int_sta() tests IWL_MVM_STATUS_IN_HW_RESTART
and doesn't really allocate a station ID for the aux
17) a new queue is added for the aux station

Note that steps from 5 to 9 aren't really part of the
problem but were described for the sake of completeness.

Once the iwl_mvm_mac_stop() is called, the device is not
accessible, meaning that step 12) can't succeed and we'll
see the following:

drivers/net/wireless/intel/iwlwifi/pcie/trans.c:2122 iwl_trans_pcie_grab_nic_access+0xc0/0x1d6 [iwlwifi]()
Timeout waiting for hardware access (CSR_GP_CNTRL 0x080403d8)
Call Trace:
[<ffffffffc03e6ad3>] iwl_trans_pcie_grab_nic_access+0xc0/0x1d6 [iwlwifi]
[<ffffffffc03e6a13>] iwl_trans_pcie_dump_regs+0x3fd/0x3fd [iwlwifi]
[<ffffffffc03dad42>] iwl_fw_error_dump+0x4f5/0xe8b [iwlwifi]
[<ffffffffc04bd43e>] __iwl_mvm_mac_start+0x5a/0x21a [iwlmvm]
[<ffffffffc04bd6d2>] iwl_mvm_mac_start+0xd4/0x103 [iwlmvm]
[<ffffffffc042d378>] drv_start+0xa1/0xc5 [iwl7000_mac80211]
[<ffffffffc045a339>] ieee80211_reconfig+0x145/0xf50 [mac80211]
[<ffffffffc044788b>] ieee80211_resume+0x62/0x66 [mac80211]
[<ffffffffc0366c5b>] wiphy_resume+0xa9/0xc6 [cfg80211]

The station id of the aux station is set to 0xff in step 3
and because we don't really allocate a new station id for
the auxliary station (as explained in 16), we end up sending
a command to the firmware asking to connect the queue
to station id 0xff. This makes the firmware crash with the
following information:

0x000002F0 | trm_hw_status0
0x00000000 | trm_hw_status1
0x00000B38 | branchlink2
0x0001978C | interruptlink1
0x00000000 | interruptlink2
0xFF080501 | data1
0xDEADBEEF | data2
0xDEADBEEF | data3
Firmware error during reconfiguration - reprobe!

in iwl_mvm_mac_stop(). We won't be able to collect debug
data anyway and when we will brought up again, we will
have a clean state from the firmware perspective.
Since we won't have IWL_MVM_STATUS_IN_HW_RESTART set in
step 12) we won't get to the 2093 ASSERT either.

Fixes: bf8b286f86fc ("iwlwifi: mvm: defer setting IWL_MVM_STATUS_IN_HW_RESTART")
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@xxxxxxxxx>
Signed-off-by: Luca Coelho <luciano.coelho@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
drivers/net/wireless/intel/iwlwifi/mvm/mac80211.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wireless/intel/iwlwifi/mvm/mac80211.c b/drivers/net/wireless/intel/iwlwifi/mvm/mac80211.c
index b15b0d84bb7e..155cc2ac0120 100644
--- a/drivers/net/wireless/intel/iwlwifi/mvm/mac80211.c
+++ b/drivers/net/wireless/intel/iwlwifi/mvm/mac80211.c
@@ -1233,12 +1233,15 @@ void __iwl_mvm_mac_stop(struct iwl_mvm *mvm)

- * Clear IN_HW_RESTART flag when stopping the hw (as restart_complete()
- * won't be called in this case).
+ * Clear IN_HW_RESTART and HW_RESTART_REQUESTED flag when stopping the
+ * hw (as restart_complete() won't be called in this case) and mac80211
+ * won't execute the restart.
* But make sure to cleanup interfaces that have gone down before/during
* HW restart was requested.
- if (test_and_clear_bit(IWL_MVM_STATUS_IN_HW_RESTART, &mvm->status))
+ if (test_and_clear_bit(IWL_MVM_STATUS_IN_HW_RESTART, &mvm->status) ||
+ &mvm->status))
ieee80211_iterate_interfaces(mvm->hw, 0,
iwl_mvm_cleanup_iterator, mvm);