linux-kernel - Re: [PATCH 2/4] usb: dwc3: Fix gadget pullup in SS mode

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Date:	Wed, 19 Sep 2012 20:24:44 +0300
From:	Felipe Balbi <balbi@...com>
To:	"Sonasath, Moiz" <m-sonasath@...com>
Cc:	balbi@...com, Kishon Vijay Abraham I <kishon@...com>,
	grant.likely@...retlab.ca, rob.herring@...xeda.com,
	rob@...dley.net, linux@....linux.org.uk, linux-usb@...r.kernel.org,
	linux-omap@...r.kernel.org, devicetree-discuss@...ts.ozlabs.org,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 2/4] usb: dwc3: Fix gadget pullup in SS mode

On Wed, Sep 19, 2012 at 11:50:53AM -0500, Sonasath, Moiz wrote:
> Felipe,
> 
> On Wed, Sep 19, 2012 at 11:04 AM, Felipe Balbi <balbi@...com> wrote:
> 
> > Hi,
> >
> > On Wed, Sep 19, 2012 at 10:02:48AM -0500, Sonasath, Moiz wrote:
> > > Felipe,
> > >
> > > On Wed, Sep 19, 2012 at 6:53 AM, Felipe Balbi <balbi@...com> wrote:
> > >
> > > > Hi,
> > > >
> > > > On Wed, Sep 19, 2012 at 05:00:27PM +0530, Kishon Vijay Abraham I wrote:
> > > > > From: Moiz Sonasath <m-sonasath@...com>
> > > > >
> > > > > For the gadget pullup functionality to work in
> > > > > SS mode it requires a particular sequence of
> > > > > toggling the run-stop bit. Here is the required
> > > > > sequence:
> > > > >
> > > > > - Set DCTL[31]
> > > > > - Clear DCTL[31]
> > > > > - Clear OMAP5430_CONTROL_CORE__PHY_POWER_USB[14]
> > > > > - Clear DCTL[8:5] = 0x00
> > > > > - Set DCTL[8:5] = 0x05
> > > > > - Wait 25 Ms
> > > > > - Set DCTL[31]
> > > > > - Set OMAP5430_CONTROL_CORE__PHY_POWER_USB[14]
> > > > >
> > > > > Tested rigourously the gadget pull-up functionality
> > > > > in bot HS and SS modes.
> > > > >
> > > > > Signed-off-by: Moiz Sonasath <m-sonasath@...com>
> > > > > Signed-off-by: Kishon Vijay Abraham I <kishon@...com>
> > > >
> > > > this needs to split into three patches:
> > > >
> > > > add new poweron field, implement it on omap-usb3, use it on
> > > > dwc3/gadget.c
> > > >
> > > > btw, I don't think the changes to run_stop bit are necessary and if
> > they
> > > > are, that'd either be a silicon errata or it would've been mentioned on
> > > > the databook. I don't remember seeing that on the databook so I'm
> > > > assuming that this is caused by a bad use of the PHY.
> > > >
> > > > Why that mdelay(25) ? why 25 ms ? That's quite a long time, actually.
> > > >
> > >
> > > Felipe, This is infact a HW bug that the Si-Val team did accept and gave
> > us
> > > this workaround sequence with the precise delay :-)
> > >
> > > Supposedly this will be fixed in ES 2.0.
> >
> > in that case this doesn't have to go to mainline since we're not
> > supporting ES1.0 in mainline :-)
> >
> > at minimum this should've come with a proper revision check anyway.
> >
> 
> Actually most of it is under a rev check :)

fair enough.

> Perhaps the last: usb_phy_shutdown(dwc->usb3_phy);
> in the else part should be in
> if (dwc->revision <= DWC3_REVISION_187A) check

Is this an OMAP errata or Synopsys errata ? If it's a Synopsys errata we
need to make sure to add the comment above the workaround, if it's an
OMAP errata, we can't apply the workaround to all users since they might
not need it, so we need a more clever scheme.

On top of that, if it's an ES1 errata, I rather not have this in
mainline since we won't support ES1 at all in mainline, which means this
workaround will be useless in a mainline kernel tree.

-- 
balbi

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