From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752419Ab3GIRPy (ORCPT ); Tue, 9 Jul 2013 13:15:54 -0400 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:45121 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751197Ab3GIRPw (ORCPT ); Tue, 9 Jul 2013 13:15:52 -0400 Date: Tue, 9 Jul 2013 19:15:50 +0200 From: Pavel Machek To: Greg KH Cc: kernel list , joe.lawrence@stratus.com, myron.stowe@redhat.com, bhelgaas@google.com Subject: Re: /sys/module/pcie_aspm/parameters/policy not writable? Message-ID: <20130709171550.GB14112@amd.pavel.ucw.cz> References: <20130709012611.GA22371@amd.pavel.ucw.cz> <20130709041321.GA30555@kroah.com> <20130709094906.GA3870@amd.pavel.ucw.cz> <20130709163726.GA11809@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130709163726.GA11809@kroah.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi! > > > > My thinkpad has rather high ping latencies... and perhaps it is due to > > > > PCIE ASPM. > > > > > > Why would that be the problem? The odds that the PCIE bus is the issue > > > seems strange to me. > > > > Aha: I guess that's why the file is not writable: > > > > pavel@amd:~$ dmesg | grep -i aspm > > ACPI FADT declares the system doesn't support PCIe ASPM, so disable it > > e1000e 0000:02:00.0: Disabling ASPM L0s L1 > > pavel@amd:~$ cat /sys/module/pcie_aspm/parameters/policy > > [default] performance powersave > > pavel@amd:~$ > > root@amd:~# echo -n performance > > > /sys/module/pcie_aspm/parameters/policy > > -su: echo: write error: Operation not permitted > > root@amd:~# > > > > But: > > 1) it should not list unavailable options > > It's a module parameter, you can't control if they are present or not > dynamically. > > > 2) operation not permitted seems like wrong error code for > > operation not supported. > > Then what should it be? I'd vote for EOPNOTSUPP /* Operation not supported on transport endpoint */ ... its certainly closer. EIO would also be an option. You are right we do not have really suitable errno. Operation not permitted is bad because it made me think that kernel denied the request for some reason, not that hardware does not support it. Thanks, Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html