linux-kernel - Re: qemu:beagle no longer booting with omap2plus

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Message-ID: <20160423214617.4d0905d2@bbrezillon>
Date:	Sat, 23 Apr 2016 21:46:17 +0200
From:	Boris Brezillon <boris.brezillon@...e-electrons.com>
To:	Guenter Roeck <linux@...ck-us.net>
Cc:	"linux-next@...r.kernel.org" <linux-next@...r.kernel.org>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Roger Quadros <rogerq@...com>,
	Brian Norris <computersforpeace@...il.com>,
	Tony Lindgren <tony@...mide.com>,
	"linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>
Subject: Re: qemu:beagle no longer booting with omap2plus_defconfig in -next

Hi Guenter,

On Sat, 23 Apr 2016 10:53:06 -0700
Guenter Roeck <linux@...ck-us.net> wrote:

> Hi,
> 
> since next-20160421, I get the following error and hang when trying to boot
> an omap2plus_defconfig image with qemu, machine 'beagle' and omap3-beagle.dtb.
> multi_v7_defconfig still works, as does machine 'beaglexm' with omap3-beagle-xm.dtb
> and omap2plus_defconfig. This is with Linaro's version of qemu.
> 
> nand: timeout while waiting for chip to become ready
> 
> The message repeats until the test times out.
> 
> Bisect points to "Merge remote-tracking branch 'nand/nand/next'" as the offending
> commit. However, the nand/nand/next branch itself is fine, as is the merge just
> prior to the nand/nand/next merge ("Merge remote-tracking branch 'l2-mtd/master'").
> 
> After some digging, I found that reverting commit "mtd: nand: omap2: Implement
> NAND ready using gpiolib" fixes the problem. What I don't know, though, is why
> the problem is only seen with omap2plus_defconfig, but not with multi_v7_defconfig,
> and why it is only seen with beagle/omap3-beagle.dtb but not with
> beaglexm/omap3-beagle-xm.dtb.
> 
> The 'rb-gpios' property is only defined in omap3-beagle.dts, but not in
> omap3-beagle-xm.dts, which may be part of the explanation. That still doesn't
> explain, though, why multi_v7_defconfig still works, but not omap2plus_defconfig.
> 
> Any ideas, anyone ?

I think you got it right for the DT changes: if rb-gpios is not
defined, it's working because the implementation fallback to "status
polling" mode, which is not relying on the new GPIO controller
implementation.
I don't know why it's working when using multi_v7_defconfig and not
with omap2_plus though (maybe a different probe order making
devm_gpiod_get_optional() return NULL instead of EPROBE_DEFER?).

And the other question I have for Roger is, do you see a reason why the
rb-gpio mode would not work?

-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com