[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] xen/arm: Set up Versatile Express timer frequency to 24 Mhz
On 06/24/2013 03:52 PM, Stefano Stabellini wrote: > On Mon, 24 Jun 2013, Tim Deegan wrote: >> At 14:10 +0100 on 24 Jun (1372083058), Julien Grall wrote: >>> On TC2, the timer frequency was set to 100 Mhz which slows down the whole >>> platform. >>> When Linux is running on bare metal, the frequency is 24 Mhz. >>> >>> "sleep 60" in dom0 takes: >>> - 4 mins with a frequency equals to 100 Mhz >>> - 1 min with a frequency equals to 24 Mhz >>> >>> Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx> >> >> Is this a problem with the vexpress (e.g. the timer runs at 24MHz >> regardless of this setting, which would explain the otherwise odd >> numbers you give above), or just that linux code assumes the timer is >> always 24MHz? >> >> If it's the latter, I think it needs to be fixed on the linux side. Xen >> can't let the guest OS dictate things like this, since we might want to >> run two guests with different OSes. Also, if linux changes its choice, >> we'd have trouble with old and new linux running together. > > Linux gets the frequency from: > > 1) device tree > 2) the arch timer register > > in this order. > Either way it should work. > > Could it be that Xen is failing to set the frequency on the versatile > express? Therefore the hardware is running the timer at a different > frequency than Xen is expecting it to? Lots of place in the DTS and the board configuration use a frequency of 24Mhz. On the arndale, the timer frequency is 24Mhz, why do we need 100Mhz on the versatile express? It seems U-boot uses SP810 to modify the clock frequency on the versatile express but I can't find documentation about the different registers. -- Julien _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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