[U-Boot] Regarding patch: http://patchwork.ozlabs.org/patch/373593/

[Marek Vasut <marex@denx.de>]

On Tuesday, April 07, 2015 at 04:52:09 PM, Ramneek Mehresh wrote:
> > -----Original Message-----
> > From: Mehresh Ramneek-B31383
> > Sent: Tuesday, April 07, 2015 8:12 PM
> > To: 'Marek Vasut'
> > Cc: u-boot; sr at denx.de
> > Subject: RE: Regarding patch: http://patchwork.ozlabs.org/patch/373593/
> > 
> > > -----Original Message-----
> > > From: Marek Vasut [mailto:marex at denx.de]
> > > Sent: Tuesday, April 07, 2015 7:44 PM
> > > To: Mehresh Ramneek-B31383
> > > Cc: u-boot; sr at denx.de
> > > Subject: Re: Regarding patch:
> > > http://patchwork.ozlabs.org/patch/373593/
> > > 
> > > On Tuesday, April 07, 2015 at 04:05:31 PM, Ramneek Mehresh wrote:
> > > > > -----Original Message-----
> > > > > From: Marek Vasut [mailto:marex at denx.de]
> > > > > Sent: Tuesday, April 07, 2015 7:22 PM
> > > > > To: Mehresh Ramneek-B31383
> > > > > Cc: u-boot; sr at denx.de
> > > > > Subject: Re: Regarding patch:
> > > > > http://patchwork.ozlabs.org/patch/373593/
> > > > > 
> > > > > On Tuesday, April 07, 2015 at 08:18:03 AM, Ramneek Mehresh wrote:
> > > > > 
> > > > > [...]
> > > > > 
> > > > > > > Hi,
> > > > > > > 
> > > > > > > Is this similar hardware bug to the one which MX6 PCIe is
> > > > > > > suffering ? On MX6, the bug is that you cannot reset the PCIe
> > > > > > > and PCIe PHY from software, which means that if you start PCIe
> > > > > > > in U-Boot, you cannot reliably use it in Linux. Furthermore,
> > > > > > > if you reset the MX6 via WDT, you cannot start PCIe reliably
> > > > > > > in Linux even if PCIe is not used in U-Boot at all.
> > > > > > > 
> > > > > > > Is this the same type of hardware screwup where the design
> > > > > > > team didn't think reset was necessary?
> > > > > > 
> > > > > > I have raised request for this feature in up-coming socs, and
> > > > > > they have agreed to provide phy shut-down in future revs.
> > > > > > However, this support is not available in current revs for which
> > > > > > the
> > 
> > code is sent.
> > 
> > > > > > What do you suggest we should do for current socs?
> > > > > 
> > > > > Hi,
> > > > > 
> > > > > I don't know, but doesn't leaving the USB running cause trouble to
> > 
> > Linux?
> > 
> > > > > I think you should at least document the reasoning why the USB
> > > > > stop is not implemented for this broken hardware.
> > > > 
> > > > Hi Marek, it's not USB controller stop, it's Phy stop which is not
> > > > supported. Controller stopping is supported.
> > > 
> > > OK, does it pose a problem for Linux ? If not, then please just
> > > document it and let's stick with what there now.
> > 
> > No, it won't create issue in Linux because Linux usb driver resets the
> > controller (which in turn resets the phy). Please suggest what's the best
> > place to document this.
> > Shall I document this inside some u-boot doc file?
> 
> I can document this inside xhci_stop() part of fsl driver. In addition,
> this will also be documented in FSL USB driver documentation.
> Please tell if this is ok.

Yes, thanks!