Re: [PATCH 1/3] hpet: allow fixed_mem32 ACPI resource type

From: Randy.Dunlap
Date: Wed Oct 12 2005 - 16:56:14 EST

(Sorry, replying from different email address; I've waited > 1 hour
for your email to arrive at ... :(
Maybe it was a bad choice.)

On Wed, 12 Oct 2005, Bjorn Helgaas wrote:

> On Wednesday 12 October 2005 12:58 pm, Randy Dunlap wrote:
> > Allow the ACPI HPET description table to use a resource type
> > of FIXED_MEM32 for the HPET reource. Use the fixed resoure
> > size of 1 KB for the HPET resource as per the HPET spec.
> I have a patch in my tree to convert HPET from an ACPI
> driver to a PNP driver, using PNPACPI. That should take
> care of issues like this.

Thanks, that's good news.

> But my patch is waiting on some PNP work by Adam to allow
> PNPACPI devices to have more than 2 IRQs.
> In the meantime, I think your patch is fine.
> > +#define HPET_RANGE_SIZE 1024 /* from HPET spec */
> Out of curiosity, why do you need this? ACPI_RSTYPE_FIXED_MEM32
> contains a length field, and my patch uses it. Did you run
> into some firmware that supplies incorrect information about the
> size of the HPET MMIO area?

a. The HPET spec says that the HPET block size is 1 KB
in section 3.2.1.

b. Table 3 (HPET description table) requires an HPET base
address (offset 40), but seems not to require a length.
However, the description text again states a fixed block size
of 1 KB.

c. Yes, I've seen descriptor.length field value of 0.
Whether it's incorrect is a discussion for an specster IMO.
At least it's debatable (by someone).

d. Yes, I would prefer to use (valid) length from the descriptor.
Maybe default to 1 KB if desc.length is 0 (?).

> Another minor HPET nit I fixed is that it currently doesn't
> use request_mem_region(). I did it in PNP terms, so it's
> waiting on Adam's work, but maybe it'd be worth an interim
> patch until that's ready.

OK, maybe you can get Bob Picco or me to add that to our
todo lists.

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