linux-kernel - Re: Kernel almost hangs when CONFIG_DRM

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Message-ID: <20110829133808.GA2025@gere.osrc.amd.com>
Date:	Mon, 29 Aug 2011 15:38:08 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Peter Zijlstra <peterz@...radead.org>,
	Alex Deucher <alexdeucher@...il.com>
CC:	Pavel Ivanov <paivanof@...il.com>,
	Michel Dänzer <michel@...nzer.net>,
	<dri-devel@...ts.freedesktop.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: Kernel almost hangs when CONFIG_DRM_RADEON=y

On Mon, Aug 29, 2011 at 03:20:21PM +0200, Peter Zijlstra wrote:
> On Sun, 2011-08-28 at 07:36 +0200, Borislav Petkov wrote:
> > > > With CONFIG_DRM_RADEON=y, the microcode is needed before it can be
> > > > loaded from userspace, so it needs to be built into the kernel as well.
> > > 
> > > How should I do that? I've tried to set all "m"s to "y" in .config and
> > > still saw this issue. Should I set some special parameter?
> > 
> > You need to add "radeon/CEDAR_pfp.bin" to CONFIG_EXTRA_FIRMWARE when you
> > configure your kernel and enable CONFIG_FIRMWARE_IN_KERNEL.
> > 
> > The radeon/CEDAR_pfp.bin file (+ leading directory, mind you) should
> > most probably be located in /lib/firmware or to whatever you have set
> > CONFIG_EXTRA_FIRMWARE_DIR so that Kbuild can find it (if not, you'll get
> > a warning at the end of the kernel build). This way, it works for both
> > radeon being =m and =y.
> 
> Should we make Kconfig pop up a dialog and ask for the whereabouts of
> these firmware thingies when you mark the driver =y? 
> 
> This all sounds like magic to me, having to know you need to add to
> EXTRA_FIRMWARE, having to know what file it needs etc.. For all intents
> and purposes =y just doesn't work and that's broken.

Yep, you make a lot of sense. I had to fumble the build/reboot cycle a
couple of times and do some code staring even to figure this out. In
the end, I copied the whole radeon/ folder from David's firmware git
repo into /lib/firmware and made radeon.ko =m again so that I don't have
to add *.bin entries to CONFIG_EXTRA_FIRMWARE each time I'm building a
kernel on a different machine.

Besides, there was this other issue on lkml today where
CONFIG_EXTRA_FIRMWARE can cause nconf to segfault when you overflow
its length of 256 by trying to include a bunch of firmware *bin files:
http://lkml.org/lkml/2011/8/29/86

Alex?

-- 
Regards/Gruss,
Boris.

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