From mboxrd@z Thu Jan 1 00:00:00 1970 From: One Thousand Gnomes Subject: Re: [RFC PATCH 3/4] tty: serial: 8250 core: add runtime pm Date: Mon, 7 Jul 2014 14:20:56 +0100 Message-ID: <20140707142056.46f61cf9@alan.etchedpixels.co.uk> References: <1404491651-1388-1-git-send-email-bigeasy@linutronix.de> <1404491651-1388-3-git-send-email-bigeasy@linutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: Received: from lxorguk.ukuu.org.uk ([81.2.110.251]:35838 "EHLO lxorguk.ukuu.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752953AbaGGNVl (ORCPT ); Mon, 7 Jul 2014 09:21:41 -0400 In-Reply-To: <1404491651-1388-3-git-send-email-bigeasy@linutronix.de> Sender: linux-serial-owner@vger.kernel.org List-Id: linux-serial@vger.kernel.org To: Sebastian Andrzej Siewior Cc: linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, balbi@ti.com, linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org, tony@atomide.com, mika.westerberg@linux.intel.com 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