Re: [PATCH 09/11] pps: low level IRQ timestamps recording.

[Rodolfo Giometti]

On Wed, Dec 02, 2009 at 04:10:44PM -0800, H. Peter Anvin wrote:
> On 12/02/2009 09:18 AM, Rodolfo Giometti wrote:
> > Add low level IRQ timestamps recording for x86 (32 and 64 bits)
> > platforms and enable UART clients in order to use it.
> > 
> > This improves PPS precision. :)
> 
> It also invokes getnstimeofday on every single interrupt, including ones
> which have absolutely nothing to do with the PPS, and are potentially
> high volume.  getnstimeofday can be a fairly expensive operation,
> especially if the best available clock is away from the CPU, or it
> requires extensive arithmetic in order to normalize the clock value...

I see, that's why I propose my patches to you: in order to have some
feedbacks for better solutions. :)

Can I add a IRQF_TIMESTAMP in order to ask to the system to record irq
timestamps for particular irq lines? The problem is that I cannot set
that flag at irq_register() time but I have to do it later... it can
be a problem?

Ciao,

Rodolfo

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