From: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>,
Stefan Wahren <stefan.wahren@i2se.com>,
Felix Fietkau <nbd@nbd.name>,
Doug Anderson <dianders@chromium.org>,
Minas Harutyunyan <hminas@synopsys.com>,
USB list <linux-usb@vger.kernel.org>,
linux-wireless <linux-wireless@vger.kernel.org>
Subject: Re: [BUG] mt76x0u: Probing issues on Raspberry Pi 3 B+
Date: Tue, 12 Feb 2019 01:06:00 +0100 [thread overview]
Message-ID: <CAJ0CqmVFVBXi5E07-ZsYojC7mP4ogpwbcDkDTeebHwX+ayz2DQ@mail.gmail.com> (raw)
In-Reply-To: <Pine.LNX.4.44L0.1902111246410.1543-100000@iolanthe.rowland.org>
>
> On Mon, 11 Feb 2019, Stanislaw Gruszka wrote:
>
> > On Mon, Feb 11, 2019 at 10:12:57AM -0500, Alan Stern wrote:
> > > On Mon, 11 Feb 2019, Lorenzo Bianconi wrote:
> > >
> > > > Here it is a different issue respect to the AMD IOMMU one, dwc2 host driver
> > > > does not implement SG I/O so probing fails. I guess it is still useful to
> > > > implement a 'legacy' mode that enable mt76 on host controllers that do not implement
> > > > SG I/O (rpi is a very common device so it will be cool to have mt76 working on
> > > > it). Moreover we are not removing functionalities, user experience will remain
> > > > the same
> > >
> > > Has anyone considered adding SG support to dwc2? It shouldn't be very
> > > difficult. The corresponding change for ehci-hcd required adding no
> > > more than about 30 lines of code.
> >
> > That would be cool. Perhaps somebody with dwc2 hardware could do this.
> >
> > However in mt76x02u we possibly would like to support other usb host
> > drivers with sg_tablesize = 0 . I would like to clarify what is correct
> > to do with such drivers.
> >
> > Is ok to pass buffer via urb->sg with urb->num_sgs = 1 ? Or maybe
> > urb->num_sgs should be 0 to pass buffer via urb->sg on such drivers ?
> > Or maybe non of above is correct and the only option that will work
> > in 100% is pass buffer via urb->transfer_buffer ?
>
> See the kerneldoc for usb_sg_init(), usb_sg_wait(), and usb_sg_cancel()
> in drivers/usb/core/message.c. These routines will always do the right
> thing -- however usb_sg_wait() must be called in process context.
>
> Alan Stern
>
Hi Alan,
I actually used usb_sg_init()/usb_sg_wait() as reference to implement
mt76u {tx/rx} datapath, but I will double-check.
I guess we should even consider if there are other usb host drivers
that do not implement SG I/O and it is worth to support.
I am wondering if the right approach is to add SG to the controller
one by one or have legacy I/O in mt76 (not sure what is the 'best'
approach)
What do you think?
Regards,
Lorenzo
next parent reply other threads:[~2019-02-12 0:06 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20190211173315.GE6292@redhat.com>
[not found] ` <Pine.LNX.4.44L0.1902111246410.1543-100000@iolanthe.rowland.org>
2019-02-12 0:06 ` Lorenzo Bianconi [this message]
2019-02-12 9:30 ` [BUG] mt76x0u: Probing issues on Raspberry Pi 3 B+ Stanislaw Gruszka
2019-02-12 11:58 ` Lorenzo Bianconi
2019-02-12 13:15 ` Stanislaw Gruszka
2019-02-14 6:49 ` Stefan Wahren
2019-02-14 9:25 ` Stanislaw Gruszka
2019-02-14 9:48 ` Stefan Wahren
2019-02-14 9:54 ` Stanislaw Gruszka
2019-02-15 7:12 ` Stanislaw Gruszka
2019-02-16 11:05 ` Stefan Wahren
2019-02-16 14:07 ` Stanislaw Gruszka
2019-02-16 19:17 ` Stefan Wahren
2019-02-18 13:52 ` Stanislaw Gruszka
2019-02-18 14:25 ` Lorenzo Bianconi
2019-02-18 14:47 ` Stanislaw Gruszka
2019-02-18 14:43 ` Felix Fietkau
2019-02-18 15:03 ` Stanislaw Gruszka
2019-02-18 18:52 ` Felix Fietkau
2019-02-19 10:42 ` Stanislaw Gruszka
2019-02-19 12:19 ` Felix Fietkau
2019-02-20 13:00 ` Stanislaw Gruszka
2019-02-20 13:22 ` Lorenzo Bianconi
2019-02-20 16:14 ` Stanislaw Gruszka
2019-02-20 16:22 ` Lorenzo Bianconi
2019-02-20 16:32 ` Stanislaw Gruszka
2019-02-20 16:36 ` Lorenzo Bianconi
2019-03-03 21:16 ` Stefan Wahren
2019-02-18 22:19 ` Stefan Wahren
2019-02-19 10:59 ` Stanislaw Gruszka
2019-02-19 12:11 ` Felix Fietkau
2019-02-19 15:40 ` Alan Stern
2019-02-20 10:20 ` Stanislaw Gruszka
2019-02-20 15:25 ` Alan Stern
2019-02-19 17:02 ` Stefan Wahren
2019-02-12 15:27 ` Alan Stern
2019-02-09 12:08 Stefan Wahren
2019-02-09 18:46 ` Lorenzo Bianconi
2019-02-09 20:29 ` Stefan Wahren
2019-02-09 20:33 ` Lorenzo Bianconi
2019-02-09 22:47 ` Stefan Wahren
2019-02-10 9:41 ` Stanislaw Gruszka
2019-02-10 10:22 ` Lorenzo Bianconi
2019-02-11 7:44 ` Stanislaw Gruszka
2019-02-11 10:04 ` Lorenzo Bianconi
2019-02-11 10:33 ` Stefan Wahren
2019-02-11 11:06 ` Lorenzo Bianconi
2019-02-11 14:04 ` Stefan Wahren
2019-02-11 15:10 ` Lorenzo Bianconi
2019-02-11 15:27 ` Stefan Wahren
2019-02-11 15:57 ` Lorenzo Bianconi
2019-02-13 7:05 ` Stefan Wahren
2019-02-11 17:22 ` Stanislaw Gruszka
2019-02-10 9:29 ` Stanislaw Gruszka
2019-02-10 16:38 ` Stefan Wahren
2019-02-10 16:52 ` Lorenzo Bianconi
2019-02-10 17:39 ` Lorenzo Bianconi
2019-02-11 7:50 ` Stanislaw Gruszka
2019-02-11 8:08 ` Stefan Wahren
2019-02-11 9:52 ` Lorenzo Bianconi
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