Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753372AbbFRIyD (ORCPT ); Thu, 18 Jun 2015 04:54:03 -0400 Received: from pandora.arm.linux.org.uk ([78.32.30.218]:39505 "EHLO pandora.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752667AbbFRIx5 (ORCPT ); Thu, 18 Jun 2015 04:53:57 -0400 Date: Thu, 18 Jun 2015 09:53:35 +0100 From: Russell King - ARM Linux To: Doug Anderson Cc: Philipp Zabel , Thierry Reding , Heiko Stuebner , David Airlie , Andy Yan , Yakir Yang , Fabio Estevam , "dri-devel@lists.freedesktop.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] drm: bridge/dw_hdmi: Filter modes > 165MHz for DVI Message-ID: <20150618085335.GF7557@n2100.arm.linux.org.uk> References: <1434582847-713-1-git-send-email-dianders@chromium.org> <20150617233040.GE7557@n2100.arm.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4131 Lines: 89 On Wed, Jun 17, 2015 at 07:52:14PM -0700, Doug Anderson wrote: > Russell, > > On Wed, Jun 17, 2015 at 4:30 PM, Russell King - ARM Linux > wrote: > > On Wed, Jun 17, 2015 at 04:14:07PM -0700, Doug Anderson wrote: > >> If you plug in a DVI monitor to your HDMI port, you need to filter out > >> clocks > 165MHz. That's because 165MHz is the maximum clock rate that > >> we can run single-link DVI at. > >> > >> If you want to run high resolutions to DVI, you'd need some type of an > >> active adapter that pretended that it was HDMI, interpreted the > >> signal, and produced a new dual link DVI signal at a lower clock rate. > >> > >> Signed-off-by: Doug Anderson > >> --- > >> Note: this patch was tested against a 3.14 kernel with backports. It > >> was only compile tested against linuxnext, but the code is > >> sufficiently similar that I'm convinced it will work there. > > > > Really? I have to wonder what your testing was... > > > > hdmi->vic = drm_match_cea_mode(mode); > > > > if (!hdmi->vic) { > > dev_dbg(hdmi->dev, "Non-CEA mode used in HDMI\n"); > > hdmi->hdmi_data.video_mode.mdvi = true; > > } else { > > dev_dbg(hdmi->dev, "CEA mode used vic=%d\n", hdmi->vic); > > hdmi->hdmi_data.video_mode.mdvi = false; > > } > > > > mdvi indicates whether the _currently set mode_ is a CEA mode or not (imho, > > it's mis-named). It doesn't indicate whether we have a HDMI display device > > or a DVI display device connected, which seems to be what you want to use > > it for below. > > > > To sort that, what you need to do is detect a HDMI display device using > > drm_detect_hdmi_monitor() on the EDID received from the device before > > parsing the modes, and save that value in a dw_hdmi struct member, and > > I'd suggest that it's a top-level struct member, not buried in 'hdmi_data' > > or 'video_mode'. > > OK, so clearly my patch won't work against mainline. I guess it's a > good thing that I pointed out that it was only tested locally (would > have been better to test against mainline, but I don't think that's so > easy since there are several unlanded patches in mainline for > Rockchip). As far as I'm aware, Freescale's original BSP version was the same, as is their later BSPs, and Jon's maintained 3.14-stable kernel. > As pointed out by others at , locally > our kernel has a slightly older version of > , which would change mdvi to be > as needed. Please don't post unreliable lkml.org URLs, please use some other archive site. I can't access this URL at the moment. > ...so I guess my change is blocked on someone reviewing/landing that > series. If that series is rejected (or is changed sufficiently so > that mdvi no longer is set via drm_detect_hdmi_monitor() then my patch > will need to be re-spun. That's not what I said. I said mdvi is set according to whether the mode being set is a CEA mode or not. We need something set according to the return value of drm_detect_hdmi_monitor(), which will tell us if the connected sink is a HDMI device or a DVI device (based upon the EDID.) A thought occurs to me this morning though: what happens if you connect a DVI monitor to an AV receiver which is then connected to this device. Does the resulting EDID contain the HDMI vendor ID? If it does, it means that drm_detect_hdmi_monitor() will return true, indicating that the connected device is HDMI, and we will still allow modes greater than 165MHz. That's probably a scenario that should be checked at some point... and it would throw a question mark over whether this is the correct approach to limit the video modes. -- FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up according to speedtest.net. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/