From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751423Ab1IWFHI (ORCPT ); Fri, 23 Sep 2011 01:07:08 -0400 Received: from home.keithp.com ([63.227.221.253]:33270 "EHLO keithp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750802Ab1IWFHG (ORCPT ); Fri, 23 Sep 2011 01:07:06 -0400 From: Keith Packard To: Jesse Barnes Cc: Dave Airlie , intel-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org Subject: Re: [Intel-gfx] [PATCH 6/9] drm/i915: Make sure eDP power is on before using aux channel In-Reply-To: <20110923082513.735b64fe@jbarnes-x220> References: <1316470923-27832-1-git-send-email-keithp@keithp.com> <1316470923-27832-7-git-send-email-keithp@keithp.com> <20110921092001.0b65bd3f@jbarnes-x220> <20110923082513.735b64fe@jbarnes-x220> User-Agent: Notmuch/0.6.1-66-ga900dda (http://notmuchmail.org) Emacs/23.3.1 (i486-pc-linux-gnu) Date: Thu, 22 Sep 2011 22:07:00 -0700 Message-ID: MIME-Version: 1.0 Content-Type: multipart/signed; boundary="=-=-="; micalg=pgp-sha1; protocol="application/pgp-signature" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --=-=-= Content-Transfer-Encoding: quoted-printable On Fri, 23 Sep 2011 08:25:13 +0530, Jesse Barnes = wrote: > Yeah that sounds good. (2) and (3) are ok cleanups, but it would be > best if they were a separate patch just in case the subtle timing > change breaks the panel power sequencing state machine. Ok, I'll split things up into tiny patches then; easier to review, and easier to try different combinations. > No I think: > 1) VDD AUX override on > 2) PPS on > 3) (delay) > 4) VDD AUX override off > is safe, I'm just worried about the timing of step (3). Ok, that seems like a nice plan to me -- just doing the PPS on sequence, and then setting VDD AUX off after PPS completes. That seems easy, and avoids leaving VDD AUX once the panel is completely running. > To fix both PCH eDP and CPU eDP in the past, I did have a version that > only used full PPS and not VDD AUX override. So it is possible, but > VDD AUX is a little cleaner since it allows us to keep the registers > locked potentially (theoretically we only actually want to unlock to > handle CPU eDP PLL enable/disable bugs and flicker-free panel fitter > downscaling). I really don't care about leaving registers locked; we're not running DOS anymore. Just doesn't make any sense to me. > But since we unlock unconditionally now, using full PPS would be ok. > Though we will have to shut it down still; PPS on to get AUX data and > EDID, then off while we program the mode and train DP, then PPS on > again. So I'm not sure it would save much. VDD AUX on or PPS has to be done to run the training anyways. > Yeah, I'm liking your delayed work much better now... Bring up the > panel early and then just modify the shutdown timeout at various points > to make sure it stays up from module_init all the way through the final > mode set (so an initial timeout of 2s or so would probably be > sufficient). The question is whether to do PPS or use VDD AUX on to start with. > Another potential optimization is to start trying AUX & i2c > transactions right after we apply VDD AUX override. The panel will > come up much faster than the T* values imply most of the time (varies > by panel). And polling the bits can get us into the actual panel > poking code much faster. While that's possible, it wasn't true on the MBA; it took almost the full T3 interval after VDD AUX was on before the EDID came back. > But I think the bottom line is to fix the EDID read (make sure the > panel is on) and the i2c stuff. Everything else is just tasty > gravy. :) Right, that is what fixed the MBA for me. > Also I think the change to prefer EDID over VBT is correct; afaik eDP > panels are required to have an EDID, so trusting that data over some > potentially untested VBT data is the right way to go. Especially when VBT comes from a BIOS emulation mess which just lies. I'll try to get a new sequence done tomorrow with these suggestions. Hope your Indian adventures are going well. =2D-=20 keith.packard@intel.com --=-=-= Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) iD8DBQFOfBP0Qp8BWwlsTdMRAqJ8AJ9CuMSwnGfX9evnDcklJ1JnwCJmfgCffh4Q 5x6qBNjubCmMgmAQQA3Cbb8= =BVx/ -----END PGP SIGNATURE----- --=-=-=--