Re: [PATCH] ath10k: Allow setting coverage class

From: Sebastian Gottschall <s.gottschall@dd-wrt.com>
To: Ben Greear <greearb@candelatech.com>,
	Benjamin Berg <benjamin@sipsolutions.net>,
	Kalle Valo <kvalo@qca.qualcomm.com>,
	linux-wireless@vger.kernel.org
Cc: Mathias Kretschmer <mathias.kretschmer@fit.fraunhofer.de>,
	ath10k@lists.infradead.org,
	Simon Wunderlich <sw@simonwunderlich.de>
Subject: Re: [PATCH] ath10k: Allow setting coverage class
Date: Fri, 29 Jul 2016 18:38:26 +0200	[thread overview]
Message-ID: <6ab675fa-4ba8-6272-9ffe-2f08c46daff1@dd-wrt.com> (raw)
In-Reply-To: <579B71B4.7080206@candelatech.com>

if these sourcecodes would be just up to date with the binaries provided 
by qca. but qca doesnt seem to care that much about it.
this is mainly also the reason why there are soo many long term 
stability issues with no resolution

Am 29.07.2016 um 17:09 schrieb Ben Greear:
> On 07/29/2016 07:52 AM, Benjamin Berg wrote:
>> On Mi, 2016-07-27 at 10:26 -0700, Ben Greear wrote:
>>> On 07/27/2016 01:33 AM, Benjamin Berg wrote:
>>>>
>>>> Unfortunately ath10k does not generally allow modifying the 
>>>> coverage class
>>>> with the stock firmware and Qualcomm has so far refused to 
>>>> implement this
>>>> feature so that it can be properly supported in ath10k. If we 
>>>> however know
>>>> the registers that need to be modified for proper operation with a 
>>>> higher
>>>> coverage class, then we can do these modifications from the driver.
>>>>
>>>> This patch implements this hack for first generation cards which 
>>>> are based
>>>> on a core that is similar to ath9k. The registers are modified in 
>>>> place and
>>>> need to be re-written every time the firmware sets them. To achieve 
>>>> this
>>>> the register status is verified after any event from the firmware.
>>>>
>>>> The coverage class may not be modified temporarily right after the 
>>>> card
>>>> re-initializes the registers. This is for example the case during 
>>>> scanning.
>>>>
>>>> A warning will be generated if the hack is not supported on the 
>>>> card or
>>>> unexpected values are hit. There is no error reporting for userspace
>>>> applications though (this is a limitation in the mac80211 driver
>>>> interface).
>>>>
>>>>>> Thanks to Sebastian Gottschall <s.gottschall@dd-wrt.com> for 
>>>>>> initially
>>>> working on a userspace support for this. This patch wouldn't have been
>>>> possible without this documentation.
>>>
>>> I would be concerned about the various resets firmware does to work 
>>> around
>>> hardware hangs as well.  I don't think any events are generated for 
>>> these, unless
>>> you count the dbglog messages?
>>
>> Yeah, I am aware of the fact that the firmware may do internal resets
>> from time to time. The interesting question (and one for which I do not
>> know the answer) is whether we get a wmi or other event under all
>> conditions where the register may be rewritten due to a reset.
>>
>> The current code will re-set the register value after any wmi event
>> including debug messages. If this is not enough, then the only solution
>> might be to periodically poll the register values instead of relying on
>> a received event.
>
> You will get a dbglog event at least most of the time, so maybe that
> will be good enough.
>
> Someone with src code and that cared could audit the code I guess, but 
> then
> that person could also just implement the feature properly in the 
> firmware
> to begin with...
>
> Thanks,
> Ben
>

-- 
Mit freundlichen Grüssen / Regards

Sebastian Gottschall / CTO

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