netdev - RE: [EXT] Prestera driver fail to probe twice

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Date: Wed, 7 Feb 2024 12:24:16 +0000
From: Elad Nachman <enachman@...vell.com>
To: Köry Maincent <kory.maincent@...tlin.com>
CC: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Taras Chornyi
	<taras.chornyi@...ision.eu>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>
Subject: RE: [EXT] Prestera driver fail to probe twice



> -----Original Message-----
> From: Köry Maincent <kory.maincent@...tlin.com>
> Sent: Wednesday, February 7, 2024 1:29 PM
> To: Elad Nachman <enachman@...vell.com>
> Cc: netdev@...r.kernel.org; Taras Chornyi <taras.chornyi@...ision.eu>;
> Thomas Petazzoni <thomas.petazzoni@...tlin.com>; Miquel Raynal
> <miquel.raynal@...tlin.com>
> Subject: Re: [EXT] Prestera driver fail to probe twice
> 
> On Wed, 7 Feb 2024 10:56:29 +0000
> Elad Nachman <enachman@...vell.com> wrote:
> 
> > > -----Original Message-----
> > > From: Köry Maincent <kory.maincent@...tlin.com>
> > > Sent: Wednesday, February 7, 2024 12:23 PM
> > > To: Elad Nachman <enachman@...vell.com>
> > > Cc: netdev@...r.kernel.org; Taras Chornyi
> > > <taras.chornyi@...ision.eu>; Thomas Petazzoni
> > > <thomas.petazzoni@...tlin.com>; Miquel Raynal
> > > <miquel.raynal@...tlin.com>
> > > Subject: Re: [EXT] Prestera driver fail to probe twice
> > >
> > > On Tue, 6 Feb 2024 18:30:33 +0000
> > > Elad Nachman <enachman@...vell.com> wrote:
> > >
> > > > Sorry, that's not how this works.
> > > >
> > > > The firmware CPU loader will only reload if the firmware crashed or exit.
> > > >
> > > > Hence, insmod on the host side will fail, as the firmware side
> > > > loader is not waiting For the host to send a new firmware, but
> > > > first for the existing firmware to exit.
> > >
> > > With the current implementation we can't rmmod/insmod the driver.
> > > Also, in case of deferring probe the same problem appears and the
> > > driver will never probe. I don't think this is a good behavior.
> > >
> > > Isn't it possible to verify that the firmware has already been sent
> > > and is working well at the probe time? Then we wouldn't try to flash it.
> >
> > Everything is possible, but that is the way the firmware interface was
> > initially designed. Changing this will break compatibility with board
> > already deployed in the field.
> 
> I don't understand, why fixing the probe by not flashing the firmware if it is
> already flashed, will break compatibility?
> Do I miss something?

First, firmware is loaded to RAM and not flashed.
Second, there is a certain control loop which dictates when the firmware loader expects new firmware by ABI, and that can only happen when the previous firmware code has terminated.

> 
> Regards,
> --
> Köry Maincent, Bootlin
> Embedded Linux and kernel engineering
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