Re: Problems when using latest git tree to boot xen on OMAP5

[Chen Baozi <baozich@gmail.com>]

On 10/07/2013 04:39 PM, Ian Campbell wrote:
> On Sun, 2013-10-06 at 22:21 +0800, Chen Baozi wrote:
>> On Oct 4, 2013, at 10:11 PM, Chen Baozi <baozich@gmail.com> wrote:
>>
>>> Hi Julien,
>>>
>>> Since Ian has merged most my OMAP5 patches, I decide to try to update my working tree to it today. However, it seems it doesn't work as expected. There mainly two kind of problems that I met:
>>>
>>> 1. It seems that xen no longer maps some of io memory regions described in dts. For example, the memory regions in "ocp" node of omap5.dtsi.
>>
>> I looked into the codes today. It is because of checking
>> dt_device_is_available() before map_device(). Some node, for
>> example /ocp/mmc@480d1000, is disabled in omap5-uevm.dts separately
>> from omap5.dtsi where it is original defined. In this case, xen won't
>> map its memory region for dom0. However, it seems dom0 kernel still
>> accesses those regions.
> 
>> I guess there would be a bug dealing with this situations?
> 
> It is certainly a bug in the kernel if it is accessing something which
> is disabled. It may also independently be a bug in the dts that this
> devices is disabled.
> 
> However in v3.12-rc4 I don't see mmc@480d1000 being disabled in
> omap5-uevm.dts and I can't see anything in the history of that file
> either. Where did your copy come from?

I'm currently working on the "omap5-v3.11-rc3" branch from
git://github.com/rogerq/linux.git, which contains a few necessary
platform patches not upstreamed. In omap5-uevm.dts, there are lines like:

253 &mmc4 {
254     status = "disabled";
255 };
256
257 &mmc5 {
258     status = "disabled";
259 };

the mmc4 refers to mmc@480d1000, which defines at omap5.dtsi:

417         mmc4: mmc@480d1000 {

I checked Linus' mainline git tree. It is the same about disabled mmc4
in omap5-uevm.dts. And the change is introduced in commit 5dd18b0 of the
mainline kernel.

Anyway, I'll see what exactly happened in the dom0 kernel dealing with
those "disabled" regions.

Cheers,

Baozi

> 
> Hopefully we won't need a converse to the device blacklist, i.e. a
> whitelist of disabled devices to pass through regardless of the DTS
> enabled state.
> 
> Ian.
> 
>