[U-Boot] [PATCH 1/2] i.MX: mxc_ipuv3_fb: add ipuv3_fb_shutdown() routine to stop IPU before bootm

[Dirk Behme]

On 23.09.2012 17:56, Stefano Babic wrote:
> On 22/09/2012 16:37, Fabio Estevam wrote:
>> On Sat, Sep 22, 2012 at 10:42 AM, Otavio Salvador
>> <otavio at ossystems.com.br>  wrote:
>>> Hello Eric,
>>>
>>> On Fri, Sep 21, 2012 at 5:36 PM, Eric Nelson
>>> <eric.nelson at boundarydevices.com>  wrote:
>>>> Signed-off-by: Eric Nelson<eric.nelson at boundarydevices.com>
>>>
>>> Did you test it in mx5 too? We seem to need to handle it in mx5 too as
>>> we had hungs in FSL kernel when using framebuffer in U-Boot. We're
>>> using a patch in kernel for workaround it but it seems your fix does
>>> what is need.
>>
>> I have just tested Eric's series on a mx53loco and it does fix the
>> kernel hang issue.
>>
>> I made some comments on this series and hopefully Eric's v2 can get
>> into 2012.10, since this is a bug fix.
>
> Ok, I am waiting for V2 and I will push it.
>
> Anyway, a question about the issue. It seems to me that it is not
> possible with IPUV3 (I have not tested myself, so my question) to get
> the u-boot splashscreen displayed on the LCD until the kernel has
> finished to boot. This could be possible (and it is possible on other
> SOC) if the IPU is loaded as module instead of statically linked to the
> kernel, and if the kernel does not touch the IPU setup. This means also
> that it should not disable the clocks used by U-Boot for the IPU.
>
> But I understand from your patch that this way is not possible on
> iMX53/MX6, and IPU must be always disabled. Is this correct ?

I'm no expert on this, so I might be wrong and people will correct me:

No, not always. It's my understanding that at the *moment* we have to 
disable the IPU in U-Boot before jumping into the kernel due to a bug 
in Sascha's kernel IPU driver:

http://lists.infradead.org/pipermail/linux-arm-kernel/2012-September/121980.html

http://lists.infradead.org/pipermail/linux-arm-kernel/2012-September/122100.html

So from my understanding, this isn't a SOC limitation. But we have to 
do it as long as the kernel's IPU driver isn't fixed.

Sorry if this is wrong ;)

Best regards

Dirk