On 05/06/2015 21:14, Chris (Christopher) Brand wrote:
Hi Julien,
Hi Chris,
When the property "clock-frequency" is present in the DT timer node, it means
that the bootloader/firmware didn't correctly configured the
CNTFRQ/CNTFRQ_EL0 on each processor.
I did try this out, and it didn't affect my results. I don't understand why,
though :-)
My test was limited as I don't have a platform where CNTFRQ/CNTFRQ_EL0
is not valid. I may have done a mistake in the code.
What I see is that in preinit_xen_time(), the call to dt_property_read_u32()
returns zero. When I built Xen, I set CONFIG_DTB_FILE, and looking at the
corresponding dts file it has a timer node with a clock-frequency property. I
know that our bootloader also creates a DTB, though, and it looks like that one
does *not* have a clock-frequency property in the timer node, so I guess Xen
ends up using that one somehow. CNTFRQ on core 0 (only) is also set to the
correct frequency, so I end up with the correct frequency in my Dom0 kernel
anyway.
dt_property_read_u32 returns 0 when it cannot find a property or because
the size of the value is not valid.
The device tree provided via CONFIG_DTB_FILE will always take precedence
to the one pass by the bootloader.
How do you set CONFIG_DTB_FILE?
I would also look to see if by any chance the wrong device tree is set
via CONFIG_DTB_FILE.
You can check what is the device tree used by dumping it from DOM0.
Thought, it may be slightly different (some nodes are rewritten). You
can dump it using dtc -I fs /proc/device-tree -O dts
Regards,
[1]
http://wiki.xen.org/wiki/Xen_ARM_with_Virtualization_Extensions/Multiboot
--
Julien Grall
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