Date:   Tue, 12 Feb 2019 14:51:00 +0100
From:   Stanislaw Gruszka <sgruszka@redhat.com>
To:     lorenzo.bianconi@redhat.com
Cc:     nbd@nbd.name, linux-wireless@vger.kernel.org
Subject: Re: [PATCH 0/4] do not use sg if not properly supported by usb
 controller
Message-ID: <20190212135100.GA15292@redhat.com>
References: <cover.1549977282.git.lorenzo@kernel.org>
 <20190212134550.GA12256@redhat.com>
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(repost with corrected Lorenzo email)

On Tue, Feb 12, 2019 at 02:45:50PM +0100, Stanislaw Gruszka wrote:
> On Tue, Feb 12, 2019 at 02:24:47PM +0100, LorenzoBianconilorenzo@kernel.org wrote:
> > From: Lorenzo Bianconi <lorenzo@kernel.org>
> > 
> > Use linear fragment and not a single usb scatter-gather buffer in mt76u
> > {tx,rx} datapath if the usb controller has sg data length constraints.
> > Moreover add disable_usb_sg module parameter in order to explicitly
> > disable scatter-gather. SG I/O is not supported by all host drivers and
> > some users have reported sg issues on AMD IOMMU.
> 
> Again. This is not right approach. SG issues should be fixed
> not workarounded.
> 
> > This series has been tested on AMD IOMMU cpus/motherboards and on rpi3+
> 
> > - rebased on top of 'fix multiple issues in mt76u error path'
> >   https://patchwork.kernel.org/cover/10804919/
> > 
> > Lorenzo Bianconi (4):
> >   mt76: usb: move mt76u_check_sg in usb.c
> >   mt76: usb: do not use sg buffers for mcu messages
> >   mt76: usb: use a linear buffer for tx/rx datapath if sg is not
> >     supported
> >   mt76: usb: introduce disable_usb_sg parameter
> > 
> >  drivers/net/wireless/mediatek/mt76/mt76.h     |  14 +-
> >  .../net/wireless/mediatek/mt76/mt76x0/usb.c   |   2 +-
> >  .../wireless/mediatek/mt76/mt76x02_usb_mcu.c  |   3 +-
> >  .../wireless/mediatek/mt76/mt76x2/usb_init.c  |   2 +-
> >  drivers/net/wireless/mediatek/mt76/usb.c      | 133 +++++++++++++-----
> >  drivers/net/wireless/mediatek/mt76/usb_mcu.c  |   5 +-
> >  6 files changed, 105 insertions(+), 54 deletions(-)
> 
> I really think my approach is simpler. Diffstat from my proposed patch is:
> 
>   drivers/net/wireless/mediatek/mt76/mt76.h |  1 +
>   drivers/net/wireless/mediatek/mt76/usb.c  | 55 ++++++++++++++---------
>   2 files changed, 36 insertions(+), 20 deletions(-)
> 
> Also this fix bug(s), presumably regression for mt76x0, should be
> backported.
> 
> Stanislaw
>