Re: [PATCH] drm: bridge/dw_hdmi: Filter modes > 165MHz for DVI

Path	csiph.com!aioe.org!bofh.it!news.nic.it!robomod
From	Russell King - ARM Linux <linux@arm.linux.org.uk>
Newsgroups	linux.kernel
Subject	Re: [PATCH] drm: bridge/dw_hdmi: Filter modes > 165MHz for DVI
Date	Thu, 18 Jun 2015 01:40:05 +0200
Message-ID	<pCv65-7Va-63@gated-at.bofh.it> (permalink)
References	<pCuMH-7y2-41@gated-at.bofh.it>
X-Original-To	Doug Anderson <dianders@chromium.org>
Dkim-Signature	v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=arm.linux.org.uk; s=pandora-2014; h=Sender:In-Reply-To:Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date; bh=bocxE/DwIzZ8KIZOs33Ap+It4dtzrjx38NHMPCP4svs=; b=cyPOpIhcDs721iNF+VKpC/sEFaTohOd/DXvKq/V5gF8csvrH4i8e8vkFowDALaodS8AD1h5TxE0ySAPsYJJiVh3vPVURxXd0IQ1id+ez92lfvIWBbt/ZhzyQybtm31ZJwyqVv3YYyqeaAUsPF4ODI79DBfpX3Nzk43oI6fiPiDk=;
MIME-Version	1.0
Content-Type	text/plain; charset=us-ascii
Content-Disposition	inline
User-Agent	Mutt/1.5.23 (2014-03-12)
Sender	robomod@news.nic.it
List-ID	<linux-kernel.vger.kernel.org>
X-Mailing-List	linux-kernel@vger.kernel.org
Approved	robomod@news.nic.it
Lines	46
Organization	linux.* mail to news gateway
X-Original-Cc	Philipp Zabel <p.zabel@pengutronix.de>, Thierry Reding <treding@nvidia.com>, Heiko Stuebner <heiko@sntech.de>, David Airlie <airlied@linux.ie>, Andy Yan <andy.yan@rock-chips.com>, Yakir Yang <ykk@rock-chips.com>, Fabio Estevam <fabio.estevam@freescale.com>, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org
X-Original-Date	Thu, 18 Jun 2015 00:30:40 +0100
X-Original-Message-ID	<20150617233040.GE7557@n2100.arm.linux.org.uk>
X-Original-References	<1434582847-713-1-git-send-email-dianders@chromium.org>
X-Original-Sender	linux-kernel-owner@vger.kernel.org
Xref	aioe.org linux.kernel:1167457

Show key headers only | View raw

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 <dianders@chromium.org>
> ---
> 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'.

-- 
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/

Back to linux.kernel | Previous | Next — Previous in thread | Find similar | Unroll thread

Thread

[PATCH] drm: bridge/dw_hdmi: Filter modes > 165MHz for DVI Doug Anderson <dianders@chromium.org> - 2015-06-18 01:20 +0200
  Re: [PATCH] drm: bridge/dw_hdmi: Filter modes > 165MHz for DVI Russell King - ARM Linux <linux@arm.linux.org.uk> - 2015-06-18 01:40 +0200

csiph-web