linux-kernel - Re: [PATCHv3 10/12] usb: dwc3: add ULPI interface support

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Date:	Tue, 5 May 2015 10:02:08 -0500
From:	Felipe Balbi <balbi@...com>
To:	Heikki Krogerus <heikki.krogerus@...ux.intel.com>
CC:	Felipe Balbi <balbi@...com>,
	David Cohen <david.a.cohen@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Baolu Lu <baolu.lu@...ux.intel.com>,
	Paul Bolle <pebolle@...cali.nl>, <linux-usb@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCHv3 10/12] usb: dwc3: add ULPI interface support

On Mon, May 04, 2015 at 03:03:45PM +0300, Heikki Krogerus wrote:
> Hi Felipe,
> 
> > > With 1.94a and newer, DWC3_GUSB3PIPECTL(0) and DWC3_GUSB2PHYCFG(0)
> > > keep their ctx over any kind of soft reset. And any configurations
> > > done to them here will take affect the latest when
> > > dwc3_core_soft_reset() is called.
> > 
> > /me goes read Databook again.
> > 
> > You're right. You're using the soft reset bit from DCTL, that only
> > resets the device side, not any global register. There are two details
> > which you don't appear to take care of, however.
> > 
> > According to Table 7-82 on Databook 2.93a (page 725), bit 30 CSFTRST,
> > it's said that "Once this bit is cleared, the software must wait at
> > least 3 PHY clocks before accessing the PHY domain".
> 
> Ok, I'll add a delay for that.
> 
> > Futher down is
> > states that "Once a new clock is selected, the PHY domain must be reset
> > for proper operation".
> 
> All PHYs will be reset once we call dwc3_core_soft_reset() and we do
> not need them to be operational before that, except in case of
> ULPI in order to register the interface. To make sure the ULPI
> interface and PHY are operational we call dwc3_soft_reset() which does
> everything needed for us. When we use DCTL.SoftRst the core will reset
> also the ULPI PHY (PHYSoftRst in DWC3_GUSB2PHYCFG(0) has no effect
> with ULPI).
> 
> So dwc3_phy_setup() configures the PHY interfaces but it does not
> initialize them or the PHYs. dwc3_core_soft_reset() continues to take
> care of that in any case, so there is no reason to duplicate it. I
> think we need to point this out in the description comment of
> dwc3_phy_setup().

sounds good to me :-)

-- 
balbi

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