netdev - Re: [PATCH v3 3/4] net: nb8800: Move HW init to ndo

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Date:   Tue, 14 Nov 2017 13:54:20 +0000
From:   Måns Rullgård <mans@...sr.com>
To:     Marc Gonzalez <marc_gonzalez@...madesigns.com>
Cc:     David Miller <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        "Linux ARM" <linux-arm-kernel@...ts.infradead.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Thibaud Cornic <thibaud_cornic@...madesigns.com>,
        Mason <slash.tmp@...e.fr>
Subject: Re: [PATCH v3 3/4] net: nb8800: Move HW init to ndo_open()

Marc Gonzalez <marc_gonzalez@...madesigns.com> writes:

> On 14/11/2017 13:40, Måns Rullgård wrote:
>
>> Marc Gonzalez wrote:
>> 
>>> Power entire ethernet block down in ndo_stop().
>>> Power it back up in ndo_open() and perform HW init.
>>> Delete nb8800_dma_stop.
>> 
>> Leave it alone, please.  Not all chips might have a separate power
>> domain for this.  Also, it works just fine on the older chips.
>
> There is no need for separate power domains. The ethernet block is
> clock-gated when it is held in reset.

So you're not powering it down then.  Please be accurate.

> The reset register is implemented on all tango3, tango4, tango5 chips.

It's still not a core feature.

> nb8800_dma_stop() is a hack.

The hack originated from your company.

> The HW dev has stated that it is not supported.  One cannot conclude
> that it "works fine" just because you've never triggered the error
> condition. (On tango5, the error condition triggers systematically.)

That sounds like a problem for tango5.

Also, I have repeated asked you what happens if the tango5 runs out of
DMA buffers under normal operation.  Does that also cause it to lock up?
If so, you have a much bigger problem on your hands.

> We have several customer bug reports on tango3 and tango4 chips complaining
> about "broken" ethernet after a link down / link up cycle. They are using a
> different driver, but it implements the same hack in enet_stop_rx().
> There is a high probability that the DMA hack is responsible, and wedged the
> RX DMA state machine.

But you have no idea what's really the problem?

-- 
Måns Rullgård