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

[Marek Vasut]

On Tuesday, April 07, 2015 at 04:42:36 PM, Ramneek Mehresh wrote:
> > -----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?

A comment in the driver source would be fine.

Best regards,
Marek Vasut