netdev - Re: Intel wireless microcode problem..

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Message-ID: <CANUX_P2KXKO9UcJbF1TniP64uY6ZJY2SqbKsoEsNqDTT0KFhdw@mail.gmail.com>
Date:	Thu, 14 Aug 2014 09:34:56 -0700
From:	Emmanuel Grumbach <egrumbach@...il.com>
To:	"Grumbach, Emmanuel" <emmanuel.grumbach@...el.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Larry Finger <Larry.Finger@...inger.net>,
	"Berg, Johannes" <johannes.berg@...el.com>,
	Intel Linux Wireless <ilw@...ux.intel.com>,
	"John W. Linville" <linville@...driver.com>,
	Linux Wireless List <linux-wireless@...r.kernel.org>,
	Network Development <netdev@...r.kernel.org>
Subject: Re: Intel wireless microcode problem..

>> >
>> > There is a new firmware that seems to help the problem. You can get it
>> > from Emmanuel's git clone. As he wrote earlier
>>
>> So quite frankly, this is *not* acceptable. We have regression policies for the
>> kernel, and this seems to be a kernel regression with the currently released
>> firmware. And I'm not downloading experimental firmware while traveling
>> with this laptop being my only way to work.
>>
>> The warnings cause *so* much message log spam that the machine is
>> occasionally spending 5% of CPU time on systemd journaling, and
>> presumably filling up disk space too.
>>
>> And the same way we don't tell people "update your buggy user space"
>> when we introduce kernel regressions, we don't tell people "try a new
>> firmware".
>>
>> People who have old systems (old distributions, old firmware, old hardware,
>> old *anything*) that works with their previous kernel, are supposed to be
>> able to upgrade their kernel with no regressions.
>> That's the rules for the kernel, and that's what the rules have been for a long
>> time. Kernel developers - including wireless driver writers
>> - had better understand that rule. It's the absolute #1 rule when it comes to
>> kernel development. This is not something new and surprosing.
>>
>> The insane amount of logging needs to be fixed. The wireless *works*, but
>> the logging is too verbose.
>>
>> Now, maybe this isn't actually a kernel regression at all - maybe triggered by
>> the horrid internet I have while traveling - but I tried twice, and when I
>> booted into the regular Fedora kernel for testing (oh, just noticed that it's
>> 3.15.8, not 3.16-based), I didn't see this kind of log spamming. So it looks like
>> a regression to me, and we have rules about regressions. And they are just
>> about the ONLY hard rules we have. But that regression rule really is very
>> very important indeed.
>>
>> The wireless *works* with the current firmware, so all that is required is to
>> make sure that the kernel stops spamming the logs so heavily. It would
>> obviously be better to try to figure out *why* the microcode error happens,
>> and what changed in the kernel to trigger it, but the "don't make the
>> machine have trouble with the insane amount of logs" is at least an
>> acceptable workaround.
>>
>> Ok?
>>
> As I said, I am tyring to repro right now - you are 100% right we are fully committed to make the current firmware work. The "experimental" firmware is just a firmware with a version problem - this is why I didn't release it formally. You can safely use it until we fix the problem.
> And we will fix it.
> And no - it is not related to the internet - this is surely a bug in our driver / firmware interface. I am currently trying to see how I can fix it - but I am also travelling...

Ok - I think I have a fix. I could reproduce your problem and I verified my fix.

diff --git a/drivers/net/wireless/iwlwifi/mvm/mac80211.c
b/drivers/net/wireless/iwlwifi/mvm/mac80211.c
index 0d6a8b7..66ef6a8 100644
--- a/drivers/net/wireless/iwlwifi/mvm/mac80211.c
+++ b/drivers/net/wireless/iwlwifi/mvm/mac80211.c
@@ -396,7 +396,8 @@ int iwl_mvm_mac_setup_register(struct iwl_mvm *mvm)
        else
                hw->wiphy->flags &= ~WIPHY_FLAG_PS_ON_BY_DEFAULT;

-       hw->wiphy->flags |= WIPHY_FLAG_SUPPORTS_SCHED_SCAN;
+       /* TODO: enable that for firmwares that don't crash only... */
+       /* hw->wiphy->flags |= WIPHY_FLAG_SUPPORTS_SCHED_SCAN; */
        hw->wiphy->max_sched_scan_ssids = PROBE_OPTION_MAX;
        hw->wiphy->max_match_sets = IWL_SCAN_MAX_PROFILES;
        /* we create the 802.11 header and zero length SSID IE. */

pull request on the way...
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