Re: [PATCH 2/9] ath9k_hw: do not override SIFS time for half/quarter channels

[Felix Fietkau <nbd@openwrt.org>]

On 2012-04-16 8:30 AM, Daniel Halperin wrote:
> On Sun, Apr 15, 2012 at 11:27 AM, Felix Fietkau <nbd@openwrt.org> wrote:
>> On 2012-04-15 8:22 PM, Daniel Halperin wrote:
>>> Felix,
>>>
>>> This whole patch series throws the NICs out of spec compliance. For
>>> instance, page 626 of the 802.11-2007 standard (Table 17-15) says that
>>> aSIFStime is 32 us in 10 MHz mode and 64 us in 5 MHz mode.
>>>
>>> This might be okay to do for certain implementations (as, apparently,
>>> AR9280/AR9380), but will break compatibility with any device obeying
>>> the standard instead.
>>>
>>> (I wonder that, if this code below still works, then it seems that you
>>> might not be properly downclocking the chips' reference clock...)
>>>
>>> Are you aware there's a standard for this? Why violate it?
>> I'm aware that there's a standard for it, but if I put in the standard
>> values, the connection gets unreliable to the point where it's almost
>> unusable. That's why I chose to use existing products with 5/10 MHz
>> support as reference instead.
>>
> 
> I hear you, but still suspect the bug's somewhere else. Violating the
> standard likely isn't the right choice unless you have a good
> reason... it sounds like you don't know why this is happening but this
> hack 'seems to work'.
> 
> (UBNT is also ath-based, right? So it's not really proof that this
> hack doesn't break compatibility..)
Right, UBNT is also ath-based, and I dumped the registers on the device
to figure out what parameters they were using, and used those as
reference for my ath9k work.
I'm not aware of *any* standard compliant 5/10 MHz product out there, do
you know any?

- Felix