Subject: ACPI

From: [email-masked] (Matthew Garrett)
Date: Tue, 26 Nov 2013 14:45:32 +0000

On Tue, Nov 26, 2013 at 01:43:40PM +0100, Linus Walleij wrote:
> On Mon, Nov 25, 2013 at 4:41 PM, Matthew Garrett <[email-masked]> wrote:
> 
> > In the past ACPI implementations handled GPIO by providing
> > methods that accessed hardware registers directly. I've seen DSDTs that
> > implement i2c entirely in ASL.
> 
> Is that common?

No, thankfully.

> Since i2c is a slow bus, can be 100kHz or so, how does that
> avoid locking the entire CPU while e.g. waiting for transactions on
> the external bus to complete?

Check status register, interruptible sleep, repeat until done.

> I have a feeling we should not recommend ARM implementers
> to go and do things like this.

Oh, absolutely.

-- 
Matthew Garrett | mjg59 at srcf.ucam.org