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Re: [Xen-devel] [RFC PATCH v2 13/22] xen/arm: its: Add virtual ITS command support

On 04/05/2015 13:58, Vijay Kilari wrote:
On Thu, Apr 30, 2015 at 7:59 PM, Julien Grall <julien.grall@xxxxxxxxxx> wrote:

On 30/04/15 14:47, Stefano Stabellini wrote:

If the devid is not within this range, the ITS won't recognize the value and
won't be able to send the interrupt.

So this is clearly not the right value.

Sure, in that case the maximum value allowed by GITS_TYPER.Devbits.
Vijay, what is the value of GITS_TYPER.Devbits on your platform?

It is 21 bits

I would imagine that 21 bits would be plenty to find an unused devid.

Alternatively we could use an inexistent function of a real device, such
as 00:00.1 (function 1 of the host bridge).

As discussed IRL, this idea sounds good to me.

Although I would be happy with any other way which ensure the devid is free.

Has prototyped with 00.00.1 as device id. But I see that Dom0 boot is
slow compared to polling mode. This could be because Dom0 has to keep
trapping on creader to check if creader is updated or not.

How did you implement the interrupt mode? Could it be improve?


Julien Grall

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