On Tue, Sep 01, 2020 at 07:38:10PM +0200, Thomas Bogendoerfer wrote:

this is the problem:

       /* Always check for received packets. */
        sgiseeq_rx(dev, sp, hregs, sregs);

so the driver will look at the rx descriptor on every interrupt, so
we cache the rx descriptor on the first interrupt and if there was
$no rx packet, we will only see it, if cache line gets flushed for
some other reason.

That means a transfer back to device ownership is missing after a
(negative) check.

kick_tx() does a busy loop checking tx descriptors,
with just sync_desc_cpu...

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]

---end quoted text---