From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jean Delvare Subject: Re: [PATCH 2/2] drm/radeon/kms: Use the standard VESA timeout for DDC channels Date: Wed, 21 Mar 2012 13:22:22 +0100 Message-ID: <201203211322.22325.jdelvare@suse.de> References: <201201281108.58888.jdelvare@suse.de> <86pqe3qoky.fsf@sumi.keithp.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mx2.suse.de (cantor2.suse.de [195.135.220.15]) by gabe.freedesktop.org (Postfix) with ESMTP id 9B16D9E797 for ; Wed, 21 Mar 2012 05:22:24 -0700 (PDT) In-Reply-To: <86pqe3qoky.fsf@sumi.keithp.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dri-devel-bounces+sf-dri-devel=m.gmane.org@lists.freedesktop.org Errors-To: dri-devel-bounces+sf-dri-devel=m.gmane.org@lists.freedesktop.org To: Keith Packard , Jerome Glisse Cc: dri-devel@lists.freedesktop.org List-Id: dri-devel@lists.freedesktop.org Hi Keith, On Sunday 29 January 2012 02:34:05 am Keith Packard wrote: > On Sat, 28 Jan 2012 11:08:58 +0100, Jean Delvare > wrote: > > The VESA specification suggests a 2.2 ms timeout on DDC channels. > > Use exactly that (as the i915 driver does) instead of hard-coding a > > jiffy count. > > The Vesa spec seems to say 2ms; at least according to the DDC/CI spec > paragraph 6.6. To be honest, I did not read it, I don't even think it is publicly available, is it? I did naively trust the comment in radeon_i2c.c: "vesa says 2.2 ms is enough". Not sure where this value came from if you claim the spec says 2 ms. Jerome, you wrote this comment in the first place, want to comment on that? The Intel drivers are using 2.2 ms too, since November 2008 (added to i915 driver by Jesse Barnes.) Maybe this all originates from X11 driver code? > usecs_to_jiffies rounds the value it gets up, so we > should never get an interval less than 2ms if we pass 2000us to it. Technically I agree, all we need to agree on is the value, 2000 us or 2200 us. I don't mind either way, I am not aware of specific complaints about the current code, I was just trying to clean things up, as hard- coding jiffy counts is bad and having different timeouts in the various drivers makes little sense IMHO. -- Jean Delvare Suse L3