Re: [PATCH] mt76: mt7603: add debugfs knob to enable/disable edcca

[Lorenzo Bianconi <lorenzo@kernel.org>]

[-- Attachment #1: Type: text/plain, Size: 2673 bytes --]

> 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 wrote:
> > > > > > > > Lorenzo Bianconi <lorenzo@kernel.org> writes:
> > > > > > > > 
> > > > > > > > > Introduce a knob in mt7603 debugfs in order to enable/disable
> > > > > > > > > edcca processing
> > > > > > > > >
> > > > > > > > > Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
> > > > > > > > 
> > > > > > > > It's good to explain what edcca does and how the file is used supposed
> > > > > > > > to be used. In other words, have a small introduction for the user.
> > > > > > > 
> > > > > > > Hi Kalle,
> > > > > > > 
> > > > > > > edcca is used for adjusting energy detect based on CCA thresholds.
> > > > > > > The code was already there so I just reported the acronym.
> > > > > > 
> > > > > > What for it is needed ?
> > > > > 
> > > > > Care to comment why EDCCA is needed at all ?
> > > > > 
> > > > > Taking that debugfs file that enable it is read-only, it looks like
> > > > > feature that nobody needs nor tests.
> > > > 
> > > > already fixed in v2
> > > > https://patchwork.kernel.org/patch/10940645/
> > > 
> > > 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, not
> > > by someone who want to test EDCCA). So again, what for EDCCA is needed ?
> > 
> > As I have already written in a previous email, ED/CCA is used to control tx power
> > according to the CCA MIB counters (e.g do not transmit if the channel busy time
> > is higher than 90% for given amount of time in a row). I guess it is required
> > 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 removed?
> 
> > Regarding file permission for mt76x02 debugfs edcca node is a typo.
> Typo or not, effectively disable the feature and show nobody is
> testing it.
> 
> 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

> 
> Stanislaw

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 228 bytes --]