imx6ul: fec: stuck on ifup after ifdown

[Sascha Hauer]

On Tue, Oct 06, 2020 at 10:44:24AM +0200, Lucas Stach wrote:
> On Mo, 2020-10-05 at 17:17 +0200, Sascha Hauer wrote:
> > Hi Stefano,
> > 
> > On Mon, Oct 05, 2020 at 02:43:15PM +0200, Manni Stefano wrote:
> > > Hi,
> > > 
> > > on a custom board based on a i.MX6UL using barebox v2020.08.1 'ifup eth0'
> > > invoked after 'ifdown eth0' stucks forever.
> > > 
> > > Have you ever experienced something similar?
> > 
> > I can confirm the same happens here on an i.MX6q board on current
> > master. I don't know what's happening here. The last thing I see is that
> > fec_tx_task_enable() is entered. Strange enough the same works on i.MX53
> > whereas on i.MX8M I get "ERROR: eth0: transmission timeout" on the
> > second ifup.
> > 
> > This is really strange. It seems fec_tx_task_enable() brings down the
> > whole SoC, but on the other hand the FEC works properly in a chainloaded
> > barebox, which should - from the view of the ethernet controller - be
> > the same as a repeated ifup/ifdown sequence.
> 
> There is a crucial difference between the two things: in a chainloaded
> Barebox we go through the FEC driver probe again, before doing the next
> ifup. When going through probe a full reset of the FEC peripheral is
> done.

Actually I thought there is a full FEC reset in fec_halt():

	writel(readl(fec->regs + FEC_X_CNTRL) | FEC_ECNTRL_RESET,
		fec->regs + FEC_X_CNTRL);

I only saw the FEC_ECNTRL_RESET bit but didn't realize this goes to a
completely unrelated register. We should have a FEC_X_CNTRL_GTS define
for this.

Given that, the fec_halt/fec_init path really looks quite different from
the fec_probe/fec_init path.

Sascha

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