From mboxrd@z Thu Jan 1 00:00:00 1970 From: Guennadi Liakhovetski Date: Fri, 04 Jun 2010 15:27:15 +0000 Subject: HDMI timing parameters problem Message-Id: List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-fbdev@vger.kernel.org Hi all I'm trying to configure an HDMI controller on an ARM based SoC, and I cannot seem to find suitable values for blanking parameters. The monitor EDID reports 1280x1024@108MHz: H_ACTIVE = 1280 H_SYNC_OFFSET = 48 H_SYNC_WIDTH = 112 H_BLANKING = 408 V_ACTIVE = 1024 V_SYNC_OFFSET = 1 V_SYNC_WIDTH = 3 V_BLANKING = 42 The HDMI controller can be programmed in one of two modes: with a preset configuration or manually specifying each parameter. The only mode that somehow works up to now is the preset 1280x720@74.25MHz. With this mode the image on the monitor is stretched vertically, but it works. Unfortunately, the controller doesn't have any preset modes for 1280x1024 or for anything close enough. So, I have to support manual geometry configuration. To reduce the number of required changes, as a first step, I'm trying to achieve the same result in manual mode, as I've got with preset, by programming 1280x720. For this I've chosen the following configuration: .xres = 1280, .yres = 720, .left_margin = 224, .right_margin = 104, .hsync_len = 40, .upper_margin = 20, .lower_margin = 5, .vsync_len = 5, which is the same, as what I'm configuring my LCD controller with. This translates to H_ACTIVE = 1280 H_SYNC_OFFSET = 104 H_SYNC_WIDTH = 40 H_BLANKING = 368 V_ACTIVE = 720 V_SYNC_OFFSET = 5 V_SYNC_WIDTH = 5 V_BLANKING = 30 With it the monitor recognises the signal, the LED goes green, but there's no image. I've done a few more tests with various configurations, but so far with no success. Can anyone suggest how to debug this? How to find the proper video mode? Thanks Guennadi --- Guennadi Liakhovetski, Ph.D. Freelance Open-Source Software Developer http://www.open-technology.de/