linux-kernel - Re: Re: Issue with fw

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Date:   Wed, 15 Sep 2021 20:59:46 +0200
From:   Jernej Škrabec <jernej.skrabec@...il.com>
To:     Saravana Kannan <saravanak@...gle.com>
Cc:     linux-sunxi@...ts.linux.dev,
        Android Kernel Team <kernel-team@...roid.com>,
        linux-kernel@...r.kernel.org
Subject: Re: Re: Issue with fw_devlink=on on 5.14

/cc linux-kernel@...r.kernel.org

Dne sreda, 15. september 2021 ob 20:36:11 CEST je Saravana Kannan napisal(a):
> On Wed, Sep 15, 2021 at 11:23 AM Saravana Kannan <saravanak@...gle.com> 
wrote:
> >
> > On Wed, Sep 15, 2021 at 11:07 AM Jernej Škrabec
> > <jernej.skrabec@...il.com> wrote:
> > >
> > > Hi Saravana!
> > >
> > > I noticed that in kernel 5.14, at least on Allwinner H3, deinterlace 
driver
> > > doesn't load anymore if fw_devlink is set to on. If I set it to off, 
driver
> > > loads and works without problems. If I remove interconnects property in 
DT
> > > node and use driver hack instead, it also loads and work ok.
> > >
> > > For reference, I speak about this node:
> > > https://elixir.bootlin.com/linux/v5.14/source/arch/arm/boot/dts/sun8i-h3.dtsi#L153
> 
> Oh the dts file please. Not dtsi. I need the full picture of dependencies.

I just dumped DTB from the board I use for testing this:
http://ix.io/3yZB

> 
> -Saravana
> 
> > >
> > > Do you have any clue why it doesn't work?
> >
> > Kinda busy today and I'll take a close look later, but if you delete
> > "interconnect" but it works, then it seems like you have no driver for
> > your "mbus" interconnect? Is that expected?

Ah, you're completely right. There is no MBUS driver (yet), since current 
purpose of that node is to determine DMA memory offsets and for that you don't 
need a driver.

There is already WIP driver for it, though:
https://github.com/crust-firmware/linux/commit/
db34316a0194dbf0fcb8eba677ef11085a06a340

> >
> > If you have a driver, then make it use the proper driver model (probe
> > a platform device).
> >
> > If you don't have a driver for it, I'm assuming you have
> > CONFIG_MODULES enabled. Otherwise, fw_devlink=on is smart enough to
> > know not to block on devices that'll never be probed.

Correct, modules are enabled.

> >
> > If you do need CONFIG_MODULES enabled, then use
> > deferred_probe_timeout=xxx so that fw_devlink doesn't wait for more
> > modules to be loaded past xxx seconds.

It's not what I want, but more that we broke default configuration and 
CONFIG_MODULES=y should really work. Is there any other way to fix this besides 
providing dummy MBUS driver? I doubt it would be accepted for backporting.

> >
> > Also I like to look up emails on lore, so when emailing me about
> > fw_devlink (or any Linux stuff in general I suppose), it'd be nice if
> > you can cc LKML.

Noted.

Best regards,
Jernej

> >
> > Thanks,
> > Saravana
>