Re: [Xen-devel] [PATCH] xen/arm: Propagate clock-frequency to DOMU if present in the DT timer node

["Chris (Christopher) Brand" <chris.brand@xxxxxxxxxxxx>]

Hi Julien,

>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.

Understood. That's why I thought it would be worthwhile posting my results :-)

>> 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?

A simple "export CONFIG_DTB_FILE=...".

>I would also look to see if by any chance the wrong device tree is set via 
>CONFIG_DTB_FILE.

I did double-check before I posted, and everything looks right to me. I 
certainly could have missed something. It does look like it's *somehow* getting 
the DT generated by the bootloader.

>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

When I do that (at a shell prompt in Dom0), the timer node does not have a 
clock-frequency property. So your patch isn't designed to help in this case 
(CNTFRQ set on core 0 only, no clock-frequency property in timer node of DT).

Chris


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