OMAP4430 failure to boot

From: tony@atomide.com (Tony Lindgren)
To: linux-arm-kernel@lists.infradead.org
Subject: OMAP4430 failure to boot
Date: Tue, 18 Jun 2013 23:43:07 -0700	[thread overview]
Message-ID: <20130619064307.GV5523@atomide.com> (raw)
In-Reply-To: <20130618183424.GD2718@n2100.arm.linux.org.uk>

* Russell King - ARM Linux <linux@arm.linux.org.uk> [130618 11:40]:
> So... the boot and build system last night managed to build its kernels
> after I dropped a couple of patches from my kernel, but we've gone from
> having both the 3430LDP and 4430SDP booting to only the 3430LDP.
> 
> Something has broken 4430SDP during the last week, and so far I've no
> idea what.  The 4430 seems to be utterly immune to any kind of debugging.
> It:
> 
> (a) doesn't produce any decompressor output because its part of the
> multiplatform kernel.  This means I've no idea if the decompressor is
> working or not.
> 
> (b) doesn't produce any output from the kernel via the use of printch()
> in the early assembly, nor via adding printascii() into printk().
> 
> Will has tested v3.10-rc6, and that works.  Will tested v3.10-rc6 plus
> arm-soc for-next, and got:
> 
> 	Error: unrecognized/unsupported machine ID (r1 = 0x00000ae7).

It's because it's DT only. I guess we could have some minimal generic
file handling that machine ID to produce an error to avoid having
to debug things?

If you have arm-soc for-next, omap4 is now DT only. So you have to
have CONFIG_ARM_APPENDED_DTB=y, CONFIG_ARM_ATAG_DTB_COMPAT=y and
CONFIG_ARM_ATAG_DTB_COMPAT_CMDLINE_EXTEND=y and append the .dtb to
zImage to boot. Or you can also update u-boot to pass the .dtb.
There are more accurate instructions in arm-soc commit b42b9181.

Moving omap4 to be DT only has been about 5900 lines of reduced data
and code so far, so that's a good reason for doing it. Most things
should work as earlier, except for the pandaboard EHCI is still missing
a fix for adding a clock alias for the auxclk. If there are things not
working, they should be quite easy to fix.

> I've just tested Linus' tip plus my tip, and that failed.  Tried Linus'
> tip.  Failed.  Removed the printch()/printascii() hooks, that got Linus'
> tip working.  I guess CONFIG_DEBUG_OMAP2UART1 is the wrong option.
> 
> And yes, Linus plus my tip also works without printascii.  So that leaves
> the questionable case of Linus tip+my tip+arm-soc tip not being bootable
> on OMAP4430 but is on OMAP3430.

Sounds like it's because of needing to boot with DT now.

Regards,

Tony