linux-kernel - Re: [RFC PATCH 3/4] tty: serial: 8250 core: add runtime pm

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 7 Jul 2014 14:20:56 +0100
From:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
To:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
	balbi@...com, linux-omap@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, tony@...mide.com,
	mika.westerberg@...ux.intel.com
Subject: Re: [RFC PATCH 3/4] tty: serial: 8250 core: add runtime pm

On Fri,  4 Jul 2014 18:34:10 +0200
Sebastian Andrzej Siewior <bigeasy@...utronix.de> wrote:

> While comparing the OMAP-serial and the 8250 part of this I noticed that
> the the latter does not use runtime-pm.

Yes it does, but 8250 parts (generally - omap presumably is special
here ?) need to be powered on to transmit/receive not just for register
access. The core uart layer implements a "pm" operation for this.

As 8250_dw uses runtime pm to implement the pm operation it's not as
simple as assumign it won't get triggered.

I *think* this is ok because the designware and other cases would take a
reference on open and drop it on close, so avoiding any confusion, but
for the register accesses on a closed port it would benefit from a
further double check with Mika especially as the suspend/resume on the
LPSS block on some Intel devices is a little bit too "interesting" for
comfort.

Otherwise however I think this is good.

Alan

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/