Date:   Tue, 12 Feb 2019 23:09:03 +0100
From:   Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
To:     Stanislaw Gruszka <sgruszka@redhat.com>
Cc:     Felix Fietkau <nbd@nbd.name>,
        linux-wireless <linux-wireless@vger.kernel.org>,
        lorenzo@kernel.org
Subject: Re: [PATCH 0/4] do not use sg if not properly supported by usb
 controller
Message-ID: <20190212220902.GA27836@localhost.localdomain>
References: <cover.1549977282.git.lorenzo@kernel.org>
 <20190212134550.GA12256@redhat.com>
 <20190212135100.GA15292@redhat.com>
 <CAJ0CqmVhH61P1V1fmhicPXwA7vHjv+Hh7h2DYbci1uDRJCyENA@mail.gmail.com>
 <20190212141725.GD12906@redhat.com>
 <20190212142528.GB24197@localhost.localdomain>
 <20190212145424.GE12906@redhat.com>
 <20190212150836.GA10823@localhost.localdomain>
 <20190212152559.GB23126@redhat.com>
 <20190212155001.GA12780@localhost.localdomain>
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> > On Tue, Feb 12, 2019 at 04:08:37PM +0100, Lorenzo Bianconi wrote:
> > > > > > What unnecessary operation ?
> > > > > 
> > > > > the ones in mt76u_fill_bulk_urb()
> > > > 
> > > > Your patches also add extra operations on hotpath due to urb->num_sgs and
> > > > dev->usb.sg_en checks.
> > > 
> > > here I guess you should use mt76u_check_sg() instead of
> > > udev->bus->sg_tablesize > 0 so I think you need to precompute it since it is in
> > > the hotpath
> > 
> > It's not necessary. If udev->bus->sg_tablesize > 0 is true and rest
> > of mt76u_check_sg() is not, we will submit urb with urb->num_sgs = 1 to
> > usb host driver, what is fine. 
> > 
> > > Moreover the RFC series has been tested by multiple users and on multiple
> > > devices
> > 
> > I know. Perhaps you could test my patch on rpi ?
> 
> sure, I will do it later

I confirm that even with Stanislaw's patch the usb dongle is properly working
on rpi3+

Regards,
Lorenzo

> 
> Regards,
> Lorenzo
> 
> > 
> > Stanislaw 
> > 
> >