Message-ID: <5317506B.1080305@connotech.com> (sfid-20140305_172708_385422_324AE29C)
Date: Wed, 05 Mar 2014 16:27:23 +0000
From: Thierry Moreau <thierry.moreau@connotech.com>
MIME-Version: 1.0
To: Larry Finger <Larry.Finger@lwfinger.net>,
	linux-wireless@vger.kernel.org
Subject: Re: rtlwifi (rtl8192ce) consistently reports EBUSY error, but scanning
 works
References: <5316C602.8020504@connotech.com> <5316CE44.5060905@lwfinger.net>
In-Reply-To: <5316CE44.5060905@lwfinger.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Sender: linux-wireless-owner@vger.kernel.org

On 03/05/14 07:12, Larry Finger wrote:
> On 03/05/2014 12:36 AM, Thierry Moreau wrote:
>> Hi!
>>
>> I am using a kind-of "linux from scratch" (i.e. Crux 3.0, 64 bits
>> Intel, kernel
>> 3.10.32) and I am stuck with a EBUSY error return from the wireless
>> driver I
>> suspect it comes from the driver behavior since it is consistent
>> either from the
>> command
>>
>> iw dev wlan1 set channel 2
>>
>> or the comand
>>
>> iwconfig wlan1 set channel 2
>>
>> (it occurred also with "iw" with a kernel where the iwconfig support
>> emulation
>> is off -- CONFIG_CFG82011_WEXT). The EBUSY error return occurs as
>> early as
>> immediately after the initial module install, and consistently
>> thereafter. The
>> wireless scanning works (reporting a nearby beacon on channel 1).

>>  [ ... ... ]

>>
>> Any suggestion about a next step in troubleshooting? Maybe trying the
>> latest
>> kernel release candidate?
>
> I use NetworkManager and I never see errors like this.
>
> You definitely should use either a newer kernel or the backports
> sources. There is a recent change that fixes a problem in rtl8192ce that
> caused interrupts to be disabled for a long time. That fix is in the
> mainline 3.14-rc5 and in the wireless-testing repo. It is in the process
> of being applied to the various stable kernels, but it is probably not
> there yet.
>
> If you just want to try that patch, it is available at
> https://lkml.org/lkml/2014/2/1/15.
>

Thanks for your reply Larry. I had seen the interrupt latency fix 
(latest release candidate) but since my problem occurs earlier than any 
wifi protocol activity, I abstained from upgrading.

Anyway since you suggested it, I moved to 3.14.0-rc5 and the problem 
occurs exactly as reported earlier (the dmesg indeed reports a different 
module load and init sequence).

 From your suggestions, I should try with tools other than iw and 
iwconfig. I thought the higher level wireless management tools would use 
the same kernel api.

Any other suggestion?

P.S. Yes, the "ip link set up wlan1" command was given. The EBUSY return 
applies equally before and after this command.

Regards,

-- Thierry Moreau