From mboxrd@z Thu Jan 1 00:00:00 1970 From: Heikki Krogerus Subject: Re: [PATCHv2 2/4] ACPI / LPSS: custom power domain for LPSS Date: Wed, 21 May 2014 13:52:58 +0300 Message-ID: <20140521105258.GB29349@xps8300> References: <1400161226-24067-1-git-send-email-heikki.krogerus@linux.intel.com> <3202918.AHHS8JP9gx@vostro.rjw.lan> <20140521100511.GA29349@xps8300> <4546817.Xm9e491t74@vostro.rjw.lan> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <4546817.Xm9e491t74@vostro.rjw.lan> Sender: linux-kernel-owner@vger.kernel.org To: "Rafael J. Wysocki" Cc: Mike Turquette , Jin Yao , Li Aubrey , Mika Westerberg , Andy Shevchenko , linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-acpi@vger.kernel.org On Wed, May 21, 2014 at 01:01:31PM +0200, Rafael J. Wysocki wrote: > On Wednesday, May 21, 2014 01:05:11 PM Heikki Krogerus wrote: > > On Tue, May 20, 2014 at 11:33:09PM +0200, Rafael J. Wysocki wrote: > > > First, is the 10 ms sleep really necessary? I'd expect the AML to take care of > > > such delays (this is not a PCI device formally). > > > > Unfortunately that is not the case. There is nothing in the AML for > > this. Mika, correct me if I'm wrong. > > > > > And because this is not a PCI device formally, why is the comment talking about > > > the PCI spec? Why is PCI relevant in any way here? > > > > Under the hood the devices are still PCI devices, even if they > > formally aren't. Maybe I should point that out in the comment.. > > > > We put the sleep there because without it there was no guarantee if > > the device was properly resumed by the time the drivers resume hooks > > were called. The symptom in case of a failure was simply that the > > registers could not be written, which leads into timeouts at least in > > case of the I2C and UART and making them unusable until the next > > suspend followed by resume. > > OK, so the msleep() is functionally necessary. Instead of talking about the > PCI in the comment, which will make a casual reader think "What the heck?", > please say something like "the delay is necessary for the subsequent register > writes to succeed on ". OK. Thanks, -- heikki