Re: [PATCH v2] ARM: dts: Add dts file for odroid XU3 board

[Sjoerd Simons <sjoerd.simons@collabora.co.uk>]

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On Wed, 2015-01-07 at 23:49 +0000, Jonathan Stone -SISA wrote:
> 
> On On Wed, 2015-01-07 at 18:37 +0000, Sjoerd Simons writes wrote:
> >On Wed, 2015-01-07 at 18:37 +0000, Anand Moon wrote:>
> [...]
> 
> >> Only 4 core cpu's are on my board. Also CpuFreq is not working.
> > 
> > Can you share some point on this.
> 
> >The defconfig is using the bL switcher, which pairs up big and little cores to make them appear as one core.. So for 8 real cores, you'll get
> >4 "virtual cores".
> 
> That configuration is appropriate for the 5420, which allegedly has a hardware bug in the cache-coherence between the Cortex-A7 block and the Cortex-A15 block.
> Newer Exynos 5 SoCs -- 5422/5800, 5620, etc -- don't have that bug. The scheduler should configured to  do HMP on all 8 (or 6) cores.
> I don't have a 5410, but I assume it has the same bug as the 5420.

Yes the kernel/scheduler could be configured like that, but
exynos_defconfig turns on bL rather then HMP. 

Now it's not unthinkable to add code/dts properties to select the
right/preferred scheduling strategy depending on the board (HMP vs. bL).
But proper HMP scheduling is still a work in progress in mainline and
iirc specifically on the XU3 there are open issue wrt. MCPM and its
secure firmware. I've added Kevin to the CC as he's been working on this
topic so should know the status a lot better then i do.

> The XU3 kernel supplied by HardKernel shows all 8 cores, and does HMP scheduling across all 8.

Yes, that's independant of the dts though as mentioned above. Also there
are still opne issues to booting up all cores on an XU3 afaik. See 
   http://www.spinics.net/lists/linux-samsung-soc/msg39523.html

> I tried v1.0 of the Odroid-XU3 DTB patch, applied to linux-next
> 20150107.  I'm only seeing 1 core running on my Odroid-XU3.  The USB
> 3.0 port works (great!) but I'm not getting any HDMI output. I didn't
> try DisplayPort.   I'll gladly try v2 of the patch on an XU3; is there
> a better base to apply the patch to?

HDMI output is broken on all exynos boards in mainline atm. For exynos
5, see the thread here:
 http://www.spinics.net/lists/linux-samsung-soc/msg40708.html

As far as a i know with the DTS as posted (just posted v3 with a small
improvement), all base functionality that can work on mainline (MMC/SD,
network, USB2, USB3) works. Some less important bits (fan control &
power sensors) are outstanding, but that really shouldn't block the
merge of the DTS.

--
Sjoerd Simons <sjoerd.simons@collabora.co.uk>
Collabora Ltd.

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