Re: [PATCH] Revert "usb: dwc3: gadget: use allocated/queued reqs for LST bit"

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

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On Mon, Oct 03, 2016 at 07:08:43PM +0300, Felipe Balbi wrote:
> 
> Hi,
> 
> ville.syrjala@linux.intel.com writes:
> > From: Ville Syrj�l� <ville.syrjala@linux.intel.com>
> >
> > This reverts commit 55a0237f8f47957163125e20ee9260538c5c341c.
> >
> > commit  55a0237f8f47 ("usb: dwc3: gadget: use allocated/queued reqs for
> > LST bit") causes my BYT FFRD8 with g_ether to behave poorly. ssh/scp
> > is very sluggish and can even stall entirely. Revert cures it.
> >
> > Cc: Felipe Balbi <felipe.balbi@linux.intel.com>
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Ville Syrj�l� <ville.syrjala@linux.intel.com>
> 
> Reverting that commit is not the best idea. Let's start with the usual:
> 
> - Kernel version
> - dmesg on both sides (host and device)
> - dwc3 tracepoints:
> 
> # mkdir -p /t
> # mount -t tracefs none /t
> # echo 8192 > /t/buffer_size_kb
> # echo 1 > /t/events/dwc3/enable
> # echo 0 > /t/events/dwc3/dwc3_readl/enable
> # echo 0 > /t/events/dwc3/dwc3_writel/enable
> 
> This should be enough to tell me what's really going on.

I've attached the (compressed due to size) dmesgs/traces from the device.
For my test I just did 'for i in `seq 1 5` ; dmesg ; done' in an ssh
session, and I did get the lag in the bad run, so presumably the trace
should have caught it. Both were on 4.8 (+ the revert for the good run).

Host side dmesg just showes me:
 usb 3-3.4: new high-speed USB device number 25 using xhci_hcd
 cdc_ether 3-3.4:1.0 usb0: register 'cdc_ether' at usb-0000:00:14.0-3.4, CDC Ethernet Device, ...
when I boot the device. Nothing extra appears when things lag around.
I'm running 4.5.something on the host.

-- 
Ville Syrj�l�
Intel OTC

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