From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sebastian Hesselbarth Subject: Re: [PATCH v4] drm/i2c: tda998x: fix sync generation and calculation Date: Thu, 20 Jun 2013 22:28:16 +0200 Message-ID: <51C365E0.1060000@gmail.com> References: <1371757563-27862-1-git-send-email-sebastian.hesselbarth@gmail.com> <20130620200624.GQ2718@n2100.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20130620200624.GQ2718@n2100.arm.linux.org.uk> Sender: linux-kernel-owner@vger.kernel.org To: Russell King - ARM Linux Cc: David Airlie , Darren Etheridge , linux-arm-kernel@lists.infradead.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org List-Id: dri-devel@lists.freedesktop.org On 06/20/2013 10:06 PM, Russell King - ARM Linux wrote: > On Thu, Jun 20, 2013 at 09:46:03PM +0200, Sebastian Hesselbarth wrote: >> + ref_pix = 3 + mode->hsync_start - mode->hdisplay; >> + de_pix_s = mode->htotal - mode->hdisplay; >> + de_pix_e = de_pix_s + mode->hdisplay; >> + hs_pix_s = mode->hsync_start - mode->hdisplay; >> + hs_pix_e = hs_pix_s + mode->hsync_end - mode->hsync_start; > > Correct, however, these can be simplified. [...] > These calculations are the same as what was originally in the driver: > > + de_start = mode->htotal - mode->hdisplay; > + de_end = mode->htotal; > + hs_start = mode->hsync_start - mode->hdisplay; > + hs_end = mode->hsync_end - mode->hdisplay; > > when it was first committed. > > This is otherwise exactly what I came up with which gets my TV working > again in HDMI mode. Russell, I am fine with any way to describe de/hs but you should notice that I also modified refpix/refline and added interlaced sync. With the original sync calculation, on some modes there was source blanking captured by TDA998x which was also visible in the output image. I chose the above description to make it more readable. Also the patch takes care of input sync and output sync inversion while the original driver always expected positive HS/VS. I tested these sync settings on 4 DVI monitors and TV sets all accepted each mode perfectly. Especially, not-so-cheap TV sets are very picky about wrong sync. Sebastian