From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benjamin Herrenschmidt Subject: Re: [PATCH] radeonfb: DDC i2c fix Date: Sat, 12 Mar 2005 10:52:17 +1100 Message-ID: <1110585137.5751.122.camel@gaston> References: <1110519970.5751.17.camel@gaston> <20050311201326.GA7379@dreamland.darkstar.lan> Reply-To: linux-fbdev-devel@lists.sourceforge.net Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Received: from sc8-sf-mx1-b.sourceforge.net ([10.3.1.11] helo=sc8-sf-mx1.sourceforge.net) by sc8-sf-list1.sourceforge.net with esmtp (Exim 4.30) id 1D9tvs-0007mp-Pt for linux-fbdev-devel@lists.sourceforge.net; Fri, 11 Mar 2005 15:52:40 -0800 Received: from gate.crashing.org ([63.228.1.57]) by sc8-sf-mx1.sourceforge.net with esmtp (TLSv1:AES256-SHA:256) (Exim 4.41) id 1D9tvq-00059o-Jg for linux-fbdev-devel@lists.sourceforge.net; Fri, 11 Mar 2005 15:52:40 -0800 In-Reply-To: <20050311201326.GA7379@dreamland.darkstar.lan> Sender: linux-fbdev-devel-admin@lists.sourceforge.net Errors-To: linux-fbdev-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Id: List-Post: List-Help: List-Subscribe: , List-Archive: Content-Type: text/plain; charset="us-ascii" To: Kronos Cc: Linux Fbdev development list , Andrew Morton On Fri, 2005-03-11 at 21:13 +0100, Kronos wrote: > Il Fri, Mar 11, 2005 at 04:46:10PM +1100, Benjamin Herrenschmidt ha scritto: > > The radeonfb code for DDC probing (like it's X.org counterpart) uses to > > leave the DDC clock & data lines asserted after the probing is complete. > > This causes problems with some Apple monitors like the new Cinema HD > > 23", who will turn themselves off when that happens. This fixes it. > > Fix is correct, but comment is not ;) After the loop SCL and SDA are > left low. Pulling them high puts the I2C bus in the stop condition. Well, they are pull-up lines. I'm not pulling them high per-se, I'm "releasing" them to their natural state, which is high ;) The ATI code does some weird shit around the i2c transfer proper, and I don't know exactly why. I don't have any spec about DDC2 though, my understand is that it's more than just i2c EEPROM though. It used to leave the 2 lines "assserted" at the end of the transfer (after the last stop condition) and that sounded wrong and causes the misbehaviour on the Apple display ... Ben. ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click