From: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
To: "Sharma, Shashank" <shashank.sharma@intel.com>
Cc: intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH 2/3] drm/i915: Reinitialize sink scrambling/TMDS clock ratio on HPD
Date: Tue, 9 Jan 2018 20:01:41 +0200 [thread overview]
Message-ID: <20180109180141.GU10981@intel.com> (raw)
In-Reply-To: <18665686-336e-2770-4bac-97323981ae72@intel.com>
On Thu, Dec 28, 2017 at 08:32:05PM +0530, Sharma, Shashank wrote:
>
>
> On 12/22/2017 11:58 PM, Ville Syrjala wrote:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> >
> > The LG 4k TV I have doesn't deassert HPD when I turn the TV off, but
> > when I turn it back on it will pulse the HPD line. By that time it has
> > forgotten everything we told it about scrambling and the clock ratio.
> > Hence if we want to get a picture out if it again we have to tell it
> > whether we're currently sending scrambled data or not. Implement
> > that via the encoder->post_hotplug() hook.
> I am not sure if I understood the problem statement correctly. Even if
> the TV triggers HPD line while turning it back, I would expect:
> - EDID read for TV's detection, which will refresh SCDC and scrambling
> capabilities
> - A new modeset will be triggered, which will program the scrambling and
> high tmds clock ratio again
> - Once HDMI controller is programmed, it will generate scrambled signals
> till next modeset / disable.
>
> So why do we need to do this ? I might be missing something, but lets
> discus about it.
The EDID is readable even when the HPD gets deasserted for a short
perios, hence we never consider the sink as being disconnected. Hence
there will be no modeset triggered by userspace.
--
Ville Syrjälä
Intel OTC
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next prev parent reply other threads:[~2018-01-09 18:01 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-22 18:28 [PATCH 1/3] drm/i915: Split encoder->hot_plug() into pre and post variants Ville Syrjala
2017-12-22 18:28 ` [PATCH 2/3] drm/i915: Reinitialize sink scrambling/TMDS clock ratio on HPD Ville Syrjala
2017-12-28 15:02 ` Sharma, Shashank
2018-01-09 18:01 ` Ville Syrjälä [this message]
2018-01-10 4:37 ` Sharma, Shashank
2018-01-10 16:23 ` Ville Syrjälä
2018-01-11 13:16 ` Sharma, Shashank
2017-12-22 18:28 ` [PATCH 3/3] drm/i915: Move SST DP link retraining into the ->post_hotplug() hook Ville Syrjala
2017-12-22 22:07 ` Manasi Navare
2017-12-22 19:52 ` ✗ Fi.CI.BAT: failure for series starting with [1/3] drm/i915: Split encoder->hot_plug() into pre and post variants Patchwork
2017-12-22 21:07 ` [PATCH 1/3] " Manasi Navare
-- strict thread matches above, loose matches on Subject: below --
2018-01-12 21:04 [PATCH 1/3] drm/i915: Convert intel_hpd_irq_event() into an encoder hotplug hook Ville Syrjala
2018-01-12 21:04 ` [PATCH 2/3] drm/i915: Reinitialize sink scrambling/TMDS clock ratio on HPD Ville Syrjala
2018-01-22 6:37 ` Sharma, Shashank
2018-01-22 19:15 ` Ville Syrjälä
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