From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Vetter Subject: Re: [PATCH 5/9] drm/i915: CPT/PPT pch dp transcoder workaround Date: Mon, 29 Oct 2012 16:38:16 +0100 Message-ID: <20121029153816.GO5691@phenom.ffwll.local> References: <1351241899-7870-1-git-send-email-daniel.vetter@ffwll.ch> <1351241899-7870-6-git-send-email-daniel.vetter@ffwll.ch> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-ee0-f49.google.com (mail-ee0-f49.google.com [74.125.83.49]) by gabe.freedesktop.org (Postfix) with ESMTP id 9D15F9E7FB for ; Mon, 29 Oct 2012 08:37:12 -0700 (PDT) Received: by mail-ee0-f49.google.com with SMTP id c1so2229805eek.36 for ; Mon, 29 Oct 2012 08:37:11 -0700 (PDT) Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org Errors-To: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org To: Paulo Zanoni Cc: Daniel Vetter , Intel Graphics Development List-Id: intel-gfx@lists.freedesktop.org On Fri, Oct 26, 2012 at 12:21:11PM -0200, Paulo Zanoni wrote: > Hi > > 2012/10/26 Daniel Vetter : > > We need to set the timing override chicken bit after fdi link training > > has completed and before we enable the dp transcoder. We also have to > > clear that bit again after disabling the pch dp transcoder. > > > > See "Graphics BSpec: vol4g North Display Engine Registers [IVB], > > Display Mode Set Sequence" and "Graphics BSpec: vol4h South Display > > Engine Registers [CPT, PPT], South Display Engine Transcoder and FDI > > Control, Transcoder Debug and DFT, TRANS_CHICKEN_2" bit 31: > > > > "Workaround : Enable the override prior to enabling the transcoder. > > Disable the override after disabling the transcoder." > > > > While at it, use the _PIPE macro for the other TRANS_DP register. > > What confuses me is that the bit name is actually "Autotrain TimingGen > Override" and after a quick check it seems we don't use autotrain. > Also, by looking at the IVB mode set sequence it seems Auto Train is > the *recommended* method since manual is listed as "testing only". So > I'm not sure if we need this code now, but it seems we could try to > implement the auto train... Well, us using manual fdi train is a different matter altogether. And since there's nothing in the docs indicating that we don't need this w/a if we don't do autotraining, I prefer to just stick it into the code. And Damien tried to do the auto training, but somehow it failed ... > Also, I'd move the code that sets/unsets the chicken bit to > intel_enable_transcoder/intel_disable_transcoder. According to my reading of the modeset sequence we need to do this after the fdi train is fully done, but before we enable the pch dp transcoder. So I think this is the right place, and I can't actually move it anyplace else. And since the pch dp transcoder is a cpt/ppt-only feature, it' fits rather naturally. Cheers, Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch