From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paulo Marques Subject: gma500: wrong pixel clock on LVDS (half the correct frequency) Date: Thu, 08 May 2014 04:21:07 +0100 Message-ID: <536AF823.9030604@masterguardian.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: Received: from prt30a.wl-dns.com (prt30a.wl-dns.com [188.93.229.73]) by gabe.freedesktop.org (Postfix) with ESMTP id 5264C6E5BF for ; Wed, 7 May 2014 21:23:18 -0700 (PDT) Received: from [188.80.91.188] (port=63274 helo=[192.168.1.70]) by prt30a.wl-dns.com with esmtpsa (TLSv1:DHE-RSA-AES128-SHA:128) (Exim 4.82) (envelope-from ) id 1WiEtQ-00089w-67 for dri-devel@lists.freedesktop.org; Thu, 08 May 2014 04:21:08 +0100 List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" To: dri-devel@lists.freedesktop.org List-Id: dri-devel@lists.freedesktop.org Hi all, I have a embedded PC system here that has an Atom Z510. The system includes a GMA500 graphics chip. The display is connected through the LVDS port and has a resolution of 1024x768. The system works ok in Windows and painfully slowly in Linux with the vesa driver, but without any flicker. Using the gma500 driver, the pixel clock seems to be half of what it should be (measured with an oscilloscope). When the image is good the pixel clock is around 65MHz. When the gma500 driver sets the resolution the pixel clock goes to around 32MHz. This gives a frame rate of around 30Hz which explains the horrible screen flicker. The performance is quite good, though. I tried running xrandr to create new modes, but the pixel clock is always wrong, no matter what I tried. The kernel version is 3.12.1. I looked at the git repository log to see if anything changed in the meanwhile that could affect this, but nothing popped up. Can you give me some pointers to what I should try next? Some obscure kernel parameter? Do you need more information? The linux graphics system changed a bit over the last few years (KMS, etc.) and I missed some of the changes, so please bare with me if I ask silly questions... Thanks in advance for any help, Paulo Marques