From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Clifton Subject: 8-bit vs. 10-bit palette mode, and LVDS dithering Date: Sat, 24 Apr 2010 17:25:10 +0100 Message-ID: <1272126310.5769.10.camel@pcjc2lap> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from ppsw-52.csi.cam.ac.uk (ppsw-52.csi.cam.ac.uk [131.111.8.152]) by gabe.freedesktop.org (Postfix) with ESMTP id 07E679E88D for ; Sat, 24 Apr 2010 09:25:12 -0700 (PDT) Received: from cpc1-cmbg11-0-0-cust151.cmbg.cable.ntl.com ([86.22.72.152]:41655 helo=[192.168.1.4]) by ppsw-52.csi.cam.ac.uk (smtp.hermes.cam.ac.uk [131.111.8.157]:465) with esmtpsa (LOGIN:pcjc2) (SSLv3:DHE-RSA-AES256-SHA:256) id 1O5iAJ-0007Pf-IO (Exim 4.70) for intel-gfx@lists.freedesktop.org (return-path ); Sat, 24 Apr 2010 17:25:11 +0100 List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: intel-gfx-bounces@lists.freedesktop.org Errors-To: intel-gfx-bounces@lists.freedesktop.org To: "intel-gfx@lists.freedesktop.org" List-Id: intel-gfx@lists.freedesktop.org Hi guys, I noticed an anomaly in the register settings on my GM45, according to PIPEBCONF, it is set in 10-bit palette mode, yet the KMS code programs the palette registers as if it is in 8-bit mode, and doesn't touch the PIPEBGCMAX{RED,GREEN,BLUE} entries for the final interpolation step. I've played with it, and I "think" my screen looks nicer with the palette reset to 8-bit mode. The KMS driver never touches this register normally, and I think it should reset it in intel_display.c's intel_crtc_load_lut. Ideally, it would be nice to have a higher resolution gamma correction. Will it work if I drm_mode_crtc_set_gamma_size(&intel_crtc->base, 129); and feed that into the 10-bit linear-interpolated lookup table? At what stage is the LVDS dithering involved here.. gamma correction probably makes a difference to whether a dither works nicely or not, and I'm wondering whether I can tune the dithering process at all. (I've got an HP laptop with a really bad colour profile, so it needs a fair bit of correction to make colours appear properly. The hardware hacker in me wonders if there is an EEPROM of gamma correction constants on the panel which could be "fixed", but sadly litte data is available from the panel manufacturer). Regards, -- Peter Clifton Electrical Engineering Division, Engineering Department, University of Cambridge, 9, JJ Thomson Avenue, Cambridge CB3 0FA Tel: +44 (0)7729 980173 - (No signal in the lab!) Tel: +44 (0)1223 748328 - (Shared lab phone, ask for me)