From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752553Ab2G0VDS (ORCPT ); Fri, 27 Jul 2012 17:03:18 -0400 Received: from mail.active-venture.com ([67.228.131.205]:65369 "EHLO mail.active-venture.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752358Ab2G0VDR (ORCPT ); Fri, 27 Jul 2012 17:03:17 -0400 X-Originating-IP: 108.223.40.66 Date: Fri, 27 Jul 2012 14:03:37 -0700 From: Guenter Roeck To: Henrik Rydberg Cc: Guenter Roeck , linux-kernel@vger.kernel.org, lm-sensors@lm-sensors.org Subject: Re: [lm-sensors] [PATCH] hwmon: (applesmc) Decode and act on read/write status codes Message-ID: <20120727210337.GA11324@roeck-us.net> References: <1343412766-552-1-git-send-email-rydberg@euromail.se> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1343412766-552-1-git-send-email-rydberg@euromail.se> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Henrik, On Fri, Jul 27, 2012 at 08:12:46PM +0200, Henrik Rydberg wrote: > The behavior of the SMC has changed several times over the years, > causing read failures in the driver. It seems the problem can be > explained by a shift in SMC speed combined with improper action on > status codes. > > We should first wait for the SMC to settle, which was the most > frequent response on the old slow machines. Then, if the SMC is busy, > we need to try again later by resending the command. This was the most > likely response until 2012. Now, with a shorter wait time, we are > again most likely to poll while the SMC is settling, and as a result > we see high failure rates on many old and new models. > > With the distinction between busy and failure, we can also wait longer > before retrying, without sacrificing speed. This seems to bring > failures down to virtually zero on all models. > > Tested on: MBA1,1 MBA3,1 MBA5,1 MBA5,2 MBP9,2 > > Tested-by: Adam Somerville > Tested-by: Hubert Eichner > Signed-off-by: Henrik Rydberg Applied. > --- > Hi Guenter, > > It turns out the mid-2012 Macbooks need additional changes in order to > work reliably. Since the needed change is a great improvement also on > other problematic machines, it would make a lot of sense if this patch > could be squeezed into the merge window. > > As I mentioned in a previous mail, backporting e70acc100 by itself is > not a good idea, but together with this patch it should be ok. > I think the patches should mature a bit in mainline. We can decide in a month or so if we want to backport them to previous releases. Thanks, Guenter