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Date:   Wed, 15 May 2019 13:13:49 +0200
From:   Lorenzo Bianconi <lorenzo@kernel.org>
To:     Stanislaw Gruszka <sgruszka@redhat.com>
Cc:     Kalle Valo <kvalo@codeaurora.org>, nbd@nbd.name,
        lorenzo.bianconi@redhat.com, linux-wireless@vger.kernel.org
Subject: Re: [PATCH] mt76: mt7603: add debugfs knob to enable/disable edcca
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> On Wed, May 15, 2019 at 12:03:44PM +0200, Lorenzo Bianconi wrote:
> > > On Wed, May 15, 2019 at 11:43:55AM +0200, Lorenzo Bianconi wrote:
> > > > > On Mon, May 13, 2019 at 11:48:37AM +0200, Stanislaw Gruszka wrote:
> > > > > > On Mon, May 13, 2019 at 10:41:28AM +0200, Lorenzo Bianconi wrot=
e:
> > > > > > > > Lorenzo Bianconi <lorenzo@kernel.org> writes:
> > > > > > > >=20
> > > > > > > > > Introduce a knob in mt7603 debugfs in order to enable/dis=
able
> > > > > > > > > edcca processing
> > > > > > > > >
> > > > > > > > > Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
> > > > > > > >=20
> > > > > > > > It's good to explain what edcca does and how the file is us=
ed supposed
> > > > > > > > to be used. In other words, have a small introduction for t=
he user.
> > > > > > >=20
> > > > > > > Hi Kalle,
> > > > > > >=20
> > > > > > > edcca is used for adjusting energy detect based on CCA thresh=
olds.
> > > > > > > The code was already there so I just reported the acronym.
> > > > > >=20
> > > > > > What for it is needed ?
> > > > >=20
> > > > > Care to comment why EDCCA is needed at all ?
> > > > >=20
> > > > > Taking that debugfs file that enable it is read-only, it looks li=
ke
> > > > > feature that nobody needs nor tests.
> > > >=20
> > > > already fixed in v2
> > > > https://patchwork.kernel.org/patch/10940645/
> > >=20
> > > I'm aware of this patch and other one for mt76x02. But so far in the
> > > sources EDCCA is disabled for mt76x02 without possibility to enable it
> > > (and this permission file issue was pointed by Kalle during review, n=
ot
> > > by someone who want to test EDCCA). So again, what for EDCCA is neede=
d ?
> >=20
> > As I have already written in a previous email, ED/CCA is used to contro=
l tx power
> > according to the CCA MIB counters (e.g do not transmit if the channel b=
usy time
> > is higher than 90% for given amount of time in a row). I guess it is re=
quired
> > by ETSI regulatory.
> But what is user case for that, i.e. who need this (it wasn't implemented=
 in
> mt76x2 since you added it on Dec 2018). What will happen if it will be re=
moved?
>=20
> > Regarding file permission for mt76x02 debugfs edcca node is a typo.
> Typo or not, effectively disable the feature and show nobody is
> testing it.
>=20
> The reason I'm asking is that seems EDCCA is the main reason to
> implement watchod for mt76x2, it wasn't necessary to have a watchdog
> as seems devices did not hung before EDCCA was added.

IIRC I added the first watchdog implementation to fix tx hangs that occur
under heavy load even using FCC regulatory (so when EDCCA processing is
disabled)

Regards,
Lorenzo

>=20
> Stanislaw

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