RE: [PATCH net-next] net: ag71xx: disable napi interrupts during probe

[Keller, Jacob E]

> -----Original Message-----
> From: Rosen Penev <rosenp@xxxxxxxxx>
> Sent: Thursday, August 29, 2024 10:47 AM
> To: Keller, Jacob E <jacob.e.keller@xxxxxxxxx>
> Cc: netdev@xxxxxxxxxxxxxxx; davem@xxxxxxxxxxxxx; edumazet@xxxxxxxxxx;
> kuba@xxxxxxxxxx; pabeni@xxxxxxxxxx; linux@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; o.rempel@xxxxxxxxxxxxxx; p.zabel@xxxxxxxxxxxxxx
> Subject: Re: [PATCH net-next] net: ag71xx: disable napi interrupts during probe
> 
> On Wed, Aug 28, 2024 at 2:05 PM Jacob Keller <jacob.e.keller@xxxxxxxxx> wrote:
> >
> >
> >
> > On 8/28/2024 1:41 PM, Rosen Penev wrote:
> > > From: Sven Eckelmann <sven@xxxxxxxxxxxxx>
> > >
> > > ag71xx_probe is registering ag71xx_interrupt as handler for gmac0/gmac1
> > > interrupts. The handler is trying to use napi_schedule to handle the
> > > processing of packets. But the netif_napi_add for this device is
> > > called a lot later in ag71xx_probe.
> > >
> > > It can therefore happen that a still running gmac0/gmac1 is triggering the
> > > interrupt handler with a bit from AG71XX_INT_POLL set in
> > > AG71XX_REG_INT_STATUS. The handler will then call napi_schedule and the
> > > napi code will crash the system because the ag->napi is not yet
> > > initialized.
> > >
> > > The gmcc0/gmac1 must be brought in a state in which it doesn't signal a
> > > AG71XX_INT_POLL related status bits as interrupt before registering the
> > > interrupt handler. ag71xx_hw_start will take care of re-initializing the
> > > AG71XX_REG_INT_ENABLE.
> > >
> > > Signed-off-by: Sven Eckelmann <sven@xxxxxxxxxxxxx>
> > > Signed-off-by: Rosen Penev <rosenp@xxxxxxxxx>
> > > ---
> >
> > The description reads like a bug fix, so I would expect this to be
> > targeted to net and have a Fixes tag indicating what commit introduced
> > the issue, maybe:
> >
> > Fixes: d51b6ce441d3 ("net: ethernet: add ag71xx driver")
> >
> > The change seems reasonable to me otherwise.
> OTOH there are currently no dual GMAC users upstream. Just single.
> 

If that’s the case, updating the description to make that clear would help.