LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Haavard Skinnemoen <hskinnemoen@atmel.com>
To: David Brownell <david-b@pacbell.net>
Cc: michael <trimarchi@gandalf.sssup.it>,
	linux-kernel@vger.kernel.org, Andrew Victor <linux@maxim.org.za>
Subject: Re: at91sam9260 wakeup on serial port
Date: Wed, 30 Jan 2008 21:34:22 +0100	[thread overview]
Message-ID: <20080130213422.504b6d53@siona> (raw)
In-Reply-To: <200801301056.13186.david-b@pacbell.net>

On Wed, 30 Jan 2008 10:56:12 -0800
David Brownell <david-b@pacbell.net> wrote:
> On Wednesday 30 January 2008, Haavard Skinnemoen wrote:
> > Yeah, although the nasty thing about UARTs is that you never know when
> > DMA really is idle.
> 
> If the UART isn't open, its DMA should be inactive.  :)
> 
> Also, after suspend() it should normally be inactive.
> (That latter is somewhat platform-specific.)

True, but can a closed or suspended UART wake the system? I guess it
could if it's really a GPIO interrupt that triggers the wakeup :-)

> > > The closest analogue to the AT91 support would map /sys/power/state:
> > > 
> > > 	standby --> to AP7 "Frozen"
> > > 	mem --> to AP7 "Stop"
> > 
> > Yes, that looks reasonable. We can also do something in between by
> > stopping most peripherals and busses. For example, keep one peripheral
> > bus and one USART running from OSC0 with everything else stopped.
> 
> Wouldn't that just be a variant of "Frozen"?  The clock API should
> be fully capable of disabling unused clocks, PLLs, and oscillators
> when the platform supports it.  It's common for lots of clocks to be
> disable even in non-suspended system states.

Yes, indeed. I was just pointing out that "Frozen" doesn't necessarily
mean what the datasheet says -- we can disable a lot of clocks manually.

> > I think we need some chip- or family-specific sleep code that knows how
> > to enter a given power state. But the specifics about how to wake the
> > system up must necessarily be board-specific (or even run-time
> > configurable.)
> 
> The sysfs wakeup attributes are the runtiime config mechanism for all
> events associated with a single device.

Right. I'm not all that familiar with the power management mechanisms
in the kernel yet, but this thread has made a few things much clearer.

Haavard

      reply	other threads:[~2008-01-30 20:34 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-01-28 11:15 michael
2008-01-28 13:56 ` Haavard Skinnemoen
2008-01-28 18:21   ` David Brownell
2008-01-28 18:44     ` trimarchi
2008-01-28 18:51     ` Haavard Skinnemoen
2008-01-30  0:37       ` michael
2008-01-30  3:44       ` David Brownell
2008-01-30 11:47         ` Haavard Skinnemoen
2008-01-30 18:56           ` David Brownell
2008-01-30 20:34             ` Haavard Skinnemoen [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20080130213422.504b6d53@siona \
    --to=hskinnemoen@atmel.com \
    --cc=david-b@pacbell.net \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux@maxim.org.za \
    --cc=trimarchi@gandalf.sssup.it \
    --subject='Re: at91sam9260 wakeup on serial port' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).