Re: [PATCH] drm/i915: Don't override output type for DDI HDMI

From: Daniel Vetter <daniel@ffwll.ch>
To: Takashi Iwai <tiwai@suse.de>
Cc: Dave Airlie <airlied@redhat.com>, intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH] drm/i915: Don't override output type for DDI HDMI
Date: Thu, 19 Nov 2015 16:51:05 +0100	[thread overview]
Message-ID: <20151119155105.GI17050@phenom.ffwll.local> (raw)
In-Reply-To: <1447931396-19147-1-git-send-email-tiwai@suse.de>

On Thu, Nov 19, 2015 at 12:09:56PM +0100, Takashi Iwai wrote:
> Currently a DDI port may register the DP hotplug handler even though
> it's used with HDMI, and the DP HPD handler overrides the encoder
> type forcibly to DP.  This caused the inconsistency on a machine
> connected with a HDMI monitor; upon a hotplug event, the DDI port is
> suddenly switched to be handled as a DP although the same monitor is
> kept connected, and this leads to the erroneous blank output.
> 
> This patch papers over the bug by excluding the previous HDMI encoder
> type from this override.  This should be fixed more fundamentally,
> e.g. by moving the encoder type reset from the HPD or by having
> individual encoder objects for HDMI and DP.  But since the bug has
> been present for a long time (3.17), it's better to have a
> quick-n-dirty fix for now, and keep working on a cleaner fix.
> 
> Bugzilla: http://bugzilla.opensuse.org/show_bug.cgi?id=955190
> Fixes: 0e32b39ceed6 ('drm/i915: add DP 1.2 MST support (v0.7)')
> Cc: <stable@vger.kernel.org> # v3.17+
> Signed-off-by: Takashi Iwai <tiwai@suse.de>

If you plug in a hmid screen (using a level-shifter adapter), then a DP
screen, does still everything work?

We rely upon the detection code to correctly adjust the encoder type,
otherwise the subsequent modeset will pick the wrong code (even when
userspace asked the kernel to light up the right connector). I'm not sure
whether this is now broken ...
-Daniel

> ---
>  drivers/gpu/drm/i915/intel_dp.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 09bdd94ca3ba..d34e64300d66 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -5153,7 +5153,8 @@ intel_dp_hpd_pulse(struct intel_digital_port *intel_dig_port, bool long_hpd)
>  	enum intel_display_power_domain power_domain;
>  	enum irqreturn ret = IRQ_NONE;
>  
> -	if (intel_dig_port->base.type != INTEL_OUTPUT_EDP)
> +	if (intel_dig_port->base.type != INTEL_OUTPUT_EDP &&
> +	    intel_dig_port->base.type != INTEL_OUTPUT_HDMI)
>  		intel_dig_port->base.type = INTEL_OUTPUT_DISPLAYPORT;
>  
>  	if (long_hpd && intel_dig_port->base.type == INTEL_OUTPUT_EDP) {
> -- 
> 2.6.3
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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