Subject: Unable to boot mainline on snow chromebook since 3.15

From: [email-masked] (Marc Zyngier)
Date: Fri, 05 Sep 2014 15:12:50 +0100

On 05/09/14 14:46, Ajay kumar wrote:
> Hi Will,
> 
> On Fri, Sep 5, 2014 at 5:52 PM, Will Deacon <[email-masked]> wrote:
>> [Looks like it's not just Rutland that can't spell the address of the
>>  mailing list today. Fixed here, so please use this post in any replies].
>>
>> On Fri, Sep 05, 2014 at 12:57:04PM +0100, Will Deacon wrote:
>>> Hi all,
>>>
>>> I'm one of the few, foolish people to try running mainline on my 5250-based
>>> Samsung Chromebook (snow). I can live without wireless, usb3 and video
>>> acceleration, so actually it makes a reasonable development platform for
>>> doing A15-based (micro)-architectural work.
>>>
>>> However, since 3.15 I've not been able to boot *any* mainline kernels on
>>> this board. I did mean to report this earlier, but I have other machines
>>> that can run mainline so this has fallen by the wayside.
>>>
>>> The problems started with 3.16, where simple-fb would fail to initialise
>>> and I lost my display. Note that I don't have a serial console on this
>>> machine (I looked at the PCB and there's no way I can solder one of those
>>> myself :) I bisected the issue at the time, and I could get my display back
>>> by removing some of the new regulator and hdmi properties from the DT. At
>>> that point, I could boot, but DMA didn't initialise for the MMC controller
>>> so I couldn't mount my root filesystem.
>>> http://www.spinics.net/lists/dri-devel/msg66740.html
>>> With 3.17-rc3, it seems a lot worse -- I don't get any output after nv-uboot
>>> (i.e. the nv-uboot screen just remains on the display, with the last line
>>> reading "Stashed 20 records").
>>>
>>> I'd usually try to debug this a bit further, but without a console it's
>>> really painful to get anywhere. I've been working with 3.15, but now I'm
>>> having to backport patches when I want to test them, which is more effort
>>> than I can be bothered with.
>>>
>>> Is anybody else running mainline on this device and are these known/fixed
>>> problems?
> AFAIK, ARM chromebooks use DRM based display drivers and the required
> patches are still not merged:
> http://www.spinics.net/lists/dri-devel/msg66740.html
> 
> Corresponding DT patches are also still not merged:
> http://www.spinics.net/lists/arm-kernel/msg358324.html
> http://www.spinics.net/lists/arm-kernel/msg358325.html
> 
> There is a patch for configs as well:
> https://www.mail-archive.com/linux-samsung-soc at vger.kernel.org/msg35828.html
> 
> Try these patches(I hope they will apply directly on 3.17-rc3) and you should
> be able to use display on snow.

As Will said, it used to work with simplefb, and it doesn't anymore. It
means someone broke mainline. So before even considering merging these
DRM patches, I'd really like to see simplefb on Snow restored to working
conditions *in mainline*.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...