linux-kernel - Re: [PATCH v3 19/19] usb: dwc3: add support for AMD NL platform

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Date:	Wed, 29 Oct 2014 09:11:46 -0500
From:	Felipe Balbi <balbi@...com>
To:	Huang Rui <ray.huang@....com>
CC:	Felipe Balbi <balbi@...com>,
	Alan Stern <stern@...land.harvard.edu>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Paul Zimmerman <Paul.Zimmerman@...opsys.com>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Jason Chang <jason.chang@....com>,
	Vincent Wan <vincent.wan@....com>, Tony Li <tony.li@....com>,
	<linux-usb@...r.kernel.org>, <linux-pci@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 19/19] usb: dwc3: add support for AMD NL platform

On Wed, Oct 29, 2014 at 05:13:43PM +0800, Huang Rui wrote:
> Hi Felipe, Paul,
> 
> On Tue, Oct 28, 2014 at 10:35:37PM +0800, Huang Rui wrote:
> > On Tue, Oct 28, 2014 at 08:38:56AM -0500, Felipe Balbi wrote:
> 
> <snip>
> 
> > > 
> > > however, as I mentioned before, the core shouldn't have to know that
> > > it's running on an AMD platform. We already support several different
> > > platforms (OMAP5, AM437x, DRA7xx, Exynos5, Exynos7, Qcom, Merrifield,
> > > Baytrail, Braswell, HAPS PCIe, and STiH407) and none of them get their
> > > $my_awesome_platform flag in dwc3, why should AMD be any different ?
> > > 
> > > This is the only part of $subject that I cannot accept because it would
> > > mean we would be giving AMD a special treatment when there shouldn't be
> > > any, for anybody.
> > > 
> > 
> > That's because I used this flag to enable below quirks on AMD NL FPGA
> > board, and FPGA flag only can be detected on core. Can I set
> > disable_scramble_quirk, dis_u3_susphy_quirk, and dis_u2_susphy_quirk
> > for all the FPGA platforms?
> > 
> > if (dwc->amd_nl_plat && dwc->is_fpga) {
> >         dwc->disable_scramble_quirk = true;
> >         dwc->dis_u3_susphy_quirk = true;
> >         dwc->dis_u2_susphy_quirk = true;
> > }
> > 
> 
> I confirmed with HW designer, these three quirks only will be needed
> on FPGA board. And these should *not* be used on non-FPGA board, as you
> known.
> 
> So I would like to use below conditions on dwc3 core. When I set these
> quirk flags in pci glue layer, then core can filter them by is_fpga
> flag to support both on FPGA and SoC. Is there any concern? If that, I
> should remove WARN_ONCE at disable_scramble flag.
> 
> if (dwc->disable_scramble_quirk && dwc->is_fpga) {..}
> 
> if (dwc->dis_u2_susphy_quirk && dwc->is_fpga) {..}
> 
> if (dwc->dis_u3_susphy_quirk && dwc->is_fpga) {..}

the problem is that somebody might need this on non-FPGA. Currently,
only AMD needs these and only on FPGA, but you never know.

I guess we can add it like this for now and once we have a real AMD
product, we drop FPGA support from AMD.

cheers

-- 
balbi

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