linux-kernel - Re: [PATCH 1/2] usb: chipidea: add xilinx zynq platform data

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Message-ID: <20150828144256.GA30916@nathan3500-linux-VM>
Date:	Fri, 28 Aug 2015 09:42:56 -0500
From:	Nathan Sullivan <nathan.sullivan@...com>
To:	Peter Chen <peter.chen@...escale.com>
Cc:	punnaiah choudary kalluri <punnaia@...inx.com>,
	sundeep subbaraya <sundeep.lkml@...il.com>,
	Subbaraya Sundeep Bhatta <sbhatta@...inx.com>,
	"robh+dt@...nel.org" <robh+dt@...nel.org>,
	"pawel.moll@....com" <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	"ijc+devicetree@...lion.org.uk" <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>
Subject: Re: [PATCH 1/2] usb: chipidea: add xilinx zynq platform data

On Fri, Aug 28, 2015 at 09:30:12AM +0800, Peter Chen wrote:
> On Thu, Aug 27, 2015 at 09:33:07AM -0500, Nathan Sullivan wrote:
> > On Thu, Aug 27, 2015 at 01:11:30PM +0530, punnaiah choudary kalluri wrote:
> > > Hi,
> > > 
> > > On Thu, Aug 27, 2015 at 10:03 AM, Peter Chen <peter.chen@...escale.com> wrote:
> > > > On Thu, Aug 27, 2015 at 10:59:22AM +0530, sundeep subbaraya wrote:
> > > >> Hi,
> > > >>
> > > >>
> > > >> On Wed, Aug 26, 2015 at 8:57 PM, Nathan Sullivan <nathan.sullivan@...com> wrote:
> > > >> > The Xilinx Zynq udc does not need the CI_HDRC_DISABLE_STREAMING flag,
> > > >> > unlike the default platform data.  Add platform data specific to the
> > > >> > Zynq udc.
> > > >> >
> > > >> > Based on a patch by the same name from the Xilinx vendor tree.
> > > >>
> > > >> I am that Xilinx guy who sent this patch :). It is in Xilinx tree as
> > > >> temporary fix and
> > > >> I did not debug further why UDC works only when streaming is enabled.
> > > >> Probably this is right time to post my question here.
> > > >> I was expecting like:
> > > >> Streaming disabled - both low bandwidth and high bandwidth systems
> > > >> should work fine
> > > >> Streaming enabled - only for high bandwidth systems
> > > >> but this is not the case, Zynq UDC works only when Streaming is enabled.
> > > >> Please correct me if I am wrong.
> > > >
> > > > You are right, stream mode disabled should work at anytime.
> > > > It is so strange why zynq UDC only works when stream mode is enabled.
> > > 
> > > I am referring the section 8.5.2 in Synopsys usb 2.0 HS controllervDoc 2.20a,
> > >  this is what it says about SDIS (streaming mode disable option)
> > > 
> > > Before activating this mode, the user must check if the TX latency
> > > buffers per endpoint are able to
> > > accommodate at least one entire maximum size packet. The RX buffer
> > > size must, at least, double the TX
> > > buffer size per endpoint. To optimize the stream disable performance,
> > > system bus burst must be set as high
> > > as possible.
> > > When the stream disable mode is used, the burst size (VUSB_HS_RX_BURST
> > > and VUSB_HS_TX_BURST)
> > > must be a integer sub-multiple of the latency buffer size
> > > (VUSB_HS_RX_DEPTH for RX buffer and
> > > VUSB_HS_TX_CHAN for the TX buffer). If this is not respected the
> > > controller will not work properly in stream
> > > disable mode.
> > > The stream disable mode should just be used in situations where the
> > > available system bandwidth is low or the
> > > system bus access latency is high, in order to avoid underruns and
> > > overruns in the latency buffers. This works
> > > for all types of endpoints, except for ISO endpoints.
> > > Such a system can't ensure the real time support that the ISO
> > > endpoints require, so the ISO endpoints are not
> > > supported when the SDIS bit is set.
> > > 
> > > Definitely we need to root cause why disable streaming mode is not
> > > working for zynq but from controller spec
> > > point of view it is possible that controller not work properly in
> > > stream disable mode.
> > > 
> > > Regards,
> > > Punnaiah
> > > 
> > 
> > Maybe the burst size isn't set correctly by default?  It does say the controller
> > won't work correctly with stream disable set and an invalid burst size.  Looks
> > like TX and RX burst both default to 16, per the Zynq manual.
> > 
> > With the stream disable bit set, the behvior we see on our hardware is
> > that priming just stops, with an outstanding transfer in memory marked
> > active in the status field by the controller.  This happens at random, even 
> > when doing single transfers at a time like with g_ether set to have a queue
> > size of 1.  With SDIS clear everything works great.  Given that the Zynq is not
> > bandwidth constrained, it seems like SDIS clear should be the default.
> > 
> 
> I suspect the possible reason is the tx buffer for each endpoint is
> small (<=512 bytes), so it can't copy one packet (assume max packet size
> for bulk) to tx buffer, then the prime can't be finished.
> 
> Would you help to dump the registers HWTXBUF ($BASE + 0x10) and DCCPARAMS
> ($BASE + 124)?
> 
> tx buffer size = ((2 ^ HWTXBUF.VUSB_HS_TX_ADD) / DCCPARAMS.DEN) *
> (DWORD_PER_BYTES)
> 
> DWORD_PER_BYTES is 4
> 
> -- 
> 
> Best Regards,
> Peter Chen

HWTXBUF is 0x80060A10, DCCPARAMS is 0xE0003124.
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