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

[Felix Fietkau <nbd@openwrt.org>]

On 2012-04-16 11:44 AM, Felix Fietkau wrote:
> 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?
By the way, I'm doing some more testing and it seems like I may be able
to get it working with standard compliant SIFS timing after all by
tweaking the rx latency settings some more.

John: Don't merge this series just yet, I'll send a v2 when I'm done
testing.

- Felix