From mboxrd@z Thu Jan 1 00:00:00 1970 From: gnomes@lxorguk.ukuu.org.uk (One Thousand Gnomes) Date: Mon, 7 Jul 2014 14:20:56 +0100 Subject: [RFC PATCH 3/4] tty: serial: 8250 core: add runtime pm In-Reply-To: <1404491651-1388-3-git-send-email-bigeasy@linutronix.de> References: <1404491651-1388-1-git-send-email-bigeasy@linutronix.de> <1404491651-1388-3-git-send-email-bigeasy@linutronix.de> Message-ID: <20140707142056.46f61cf9@alan.etchedpixels.co.uk> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Fri, 4 Jul 2014 18:34:10 +0200 Sebastian Andrzej Siewior 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