Re: [PATCH] imx{5,6}: reset otg port after usb-serial boot

[Michael Grzeschik <mgr@pengutronix.de>]

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On Mon, Aug 27, 2018 at 09:52:24AM +0200, Sascha Hauer wrote:
> On Mon, Aug 27, 2018 at 09:47:41AM +0200, Michael Grzeschik wrote:
> > On Fri, Aug 24, 2018 at 05:18:02PM -0300, Fabio Estevam wrote:
> > > Hi Michael,
> > > 
> > > On Fri, Aug 24, 2018 at 4:55 PM, Michael Grzeschik <mgr@pengutronix.de> wrote:
> > > 
> > > > I get that it is not safe to toggle bits if the clock is not
> > > > there. We could check for the bootsource. Is it possible to
> > > > ensure that we are started by imx-usb-loader?
> > > 
> > > It is possible to determine if we have started via USB download mode.
> > > 
> > > Check the is_boot_from_usb() implementation in U-Boot for a reference.
> > 
> > Right, So it seems to be safe to reach for the phys registers on mx6.
> > 
> > On mx5 and similar we have a nop phy and the only way to
> > communicate with it is through usbmisc, which is also in the
> > register space that leads to a hang if one clock is missing.
> > 
> > I will search for another solutions on those SoCs.
> 
> It's not necessary to ask for the bootsource. You just have to enable
> the clocks necessary to access the USB registers. Or the other way
> round: When the clocks are not enabled already, you could assume we have
> not booted from USB.

Right, I think enabling the clocks is a little bit more safe
as we otherwise would need to ensure that nobody slips in
a DCD that already ungates all clocks.

mgr

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