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Subject: Re: [PATCH] rtw88: add debugfs to fix tx rate
To:     Johannes Berg <johannes@sipsolutions.net>,
        Brian Norris <briannorris@chromium.org>
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Cc:     Tony Chuang <yhchuang@realtek.com>,
        Kalle Valo <kvalo@codeaurora.org>,
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From:   Ben Greear <greearb@candelatech.com>
Message-ID: <bdac6a5b-df73-3b8d-5fd2-3a5038563da4@candelatech.com>
Date:   Mon, 25 May 2020 09:16:58 -0700
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On 05/25/2020 02:07 AM, Johannes Berg wrote:
> On Wed, 2020-03-25 at 11:14 -0700, Brian Norris wrote:
>> On Wed, Mar 25, 2020 at 8:52 AM Ben Greear <greearb@candelatech.com> wrote:
>>> On 03/24/2020 10:16 PM, Brian Norris wrote:
>>>> Sure, but if you mask out all but 1 bitrate...voila! A fixed rate!
>>>
>>> So, see this thread from a while back.  Has anyone even *tried* to use
>>> this API you are proposing?
>>
>> Yes, in fact, I have! Which is why I noted:
>>
>>>> Now, there are other problems, like the others that Ben mentioned: the
>>>> rest of the mac80211 framework doesn't like it too much if you really
>>>> disable all but 1 rate (arguably a mac80211 bug -- but not a nl80211
>>>> bug)
>>> http://lists.infradead.org/pipermail/ath10k/2017-October/010291.html
>>
>> I hadn't seen that thread. So it sounds like maybe Johannes isn't
>> quite on the same page as Johannes ;)
>
> Hah. Happens all the time, not sure what that other Johannes is thinking
> ;-)
>
> More seriously though, I'm a bit lost now (and a big part of that is
> probably because I'm replying to a 2 months old thread, sorry).
>
>> If we're going to be particular about matching the AP's basic rates,
>> then this API is indeed probably not useful for the "single fixed rate
>> [for debugging/testing]" use case.
>>
>>>      mac80211: Revert some of e8e4f5, fixes setting single rate in ath10k.
>>
>> Commit e8e4f5 was an unfortunate consequence of the stuff I mentioned
>> earlier about how Chrome OS used to use SET_TX_BITRATE_MAX -- we
>> weren't nuanced about it at all, so we might configure a set of
>> bitrates that doesn't intersect at all with the AP's BasicRates. That
>> does make it hard for the driver/framework to decide what to do: do we
>> listen to the user, or to the AP? Incidentally, that's also one reason
>> why Chrome OS no longer uses the API; it was too big of a hammer for
>> what we want (initial-connection reliability), and required us to be
>> more delicate about {Supported,Basic}Rates than we really wanted to.
>
> Right.
>
> But I'm not sure why Ben needs to just do a pr_err()? Shouldn't that
> just not happen?

Try setting a single rate on ath10k.  It will not work unless you add my
patch.

I put a pr_err in there because you (or whoever pushed the regression upstream)
thought it was a problem to set a single rate, so I wanted to warn the user
but also let the action work.

Thanks,
Ben

>
> Hmm.
>
> johannes
>

-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com