linux-kernel - Re: [PATCH] usb: dwc3: exynos: remove usb_phy

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Date:	Thu, 28 Aug 2014 12:29:52 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Cc:	Vivek Gautam <gautam.vivek@...sung.com>,
	Felipe Balbi <balbi@...com>, Olof Johansson <olof@...om.net>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	Linux USB Mailing List <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Alan Stern <stern@...land.harvard.edu>
Subject: Re: [PATCH] usb: dwc3: exynos: remove usb_phy_generic support

On Thu, Aug 28, 2014 at 08:11:04PM +0200, Bartlomiej Zolnierkiewicz wrote:
> 
> [ added Alan and Greg to cc: ]
> 
> Hi,
> 
> On Wednesday, August 27, 2014 11:42:25 PM Vivek Gautam wrote:
> > Hi Baltlomiej,
> > 
> > 
> > On Wed, Aug 27, 2014 at 1:22 PM, Bartlomiej Zolnierkiewicz
> > <b.zolnierkie@...sung.com> wrote:
> > > dwc3 driver is using the new Exynos5 SoC series USB DRD PHY driver
> > > (PHY_EXYNOS5_USBDRD which selects GENERIC_PHY) as can be seen by
> > > looking at the following commits:
> > >
> > >   7a4cf0fde054 ("ARM: dts: Update DWC3 usb controller to use new
> > >   phy driver for exynos5250")
> > >
> > >   f070267b5fc1 ("ARM: dts: Enable support for DWC3 controller for
> > >   exynos5420")
> > >
> > > Thus remove unused usb_phy_generic support from dwc3 Exynos glue
> > > layer.
> > >
> > > [ The code that is being removed is harmful in the context of
> > >   multi_v7_defconfig and enabling "EHCI support for Samsung
> > >   S5P/EXYNOS SoC Series" (USB_EHCI_EXYNOS) + "OHCI support for
> > >   Samsung S5P/EXYNOS SoC Series" (USB_OHCI_EXYNOS) because "EHCI
> > >   support for OMAP3 and later chips" (USB_EHCI_HCD_OMAP) selects
> > >   "NOP USB Transceiver Driver" (NOP_USB_XCEIV).  NOP USB driver
> > >   attaches itself to usb_phy_generic platform devices created by
> > >   dwc3 Exynos glue layer and later causes Exynos EHCI driver to
> > >   fail probe and Exynos OHCI driver to hang on probe (as observed
> > >   on Exynos5250 Arndale board). ]
> > 
> > The issue with EHCI and OHCI on exynos platforms is that until now
> > they also request
> > usb-phy and only later if they don't find one, they go ahead and get a
> > 'phy' generic.
> > 
> > Fortunately we missed this issue with exynos_defconfig, and as you rightly
> > mentioned with multi_v7_defconfig, the NOP_USB_XCEIV gets enabled and
> > EHCI and OHCI exynos get no-op usb-phy, which actually blocks EHCI/OHCI from
> > initializing the real PHYs.
> > 
> > This issue is resolved with patches:
> > [PATCH v2 1/2] usb: host: ehci-exynos: Remove unnecessary usb-phy support
> > [PATCH v2 2/2] usb: host: ohci-exynos: Remove unnecessary usb-phy support
> > wherein we are completely removing the usb-phy support from ehci/ohci-exynos.
> > So with these patches we should not see the issue mentioned by you.
> 
> Indeed, your patches fix the issue.
> 
> Greg, could these two patches ([1] & [2]) get merged quickly, pretty please
> (they were already acked by Alan)?  They are not a mere cleanups because
> they fix the actual problem with using multi_v7_defconfig which in turn has
> been blocking Olof's defconfig update patch [3] for quite some time now.
> Moreover these patches are limited to Exynos host drivers so they should be
> pretty safe when it comes to potential regressions.
> 
> [1] http://www.spinics.net/lists/linux-usb/msg112294.html
> [2] http://www.spinics.net/lists/linux-usb/msg112293.html
> [3] http://www.spinics.net/lists/arm-kernel/msg349654.html

merged for 3.18-rc1, or do you "need" them for 3.17-final?

I already reverted one patch for exynos for 3.17-final that is sitting
in my tree to go to Linus soon as you all didn't seem to want it
anymore, so I'm getting really confused here...

thanks,

greg k-h
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