Re: [PATCH] drm/i915: Don't trust the DP_DETECT bit for eDP ports on CHV

[Jani Nikula <jani.nikula@linux.intel.com>]

On Mon, 13 Oct 2014, Damien Lespiau <damien.lespiau@intel.com> wrote:
> On Thu, Oct 09, 2014 at 07:37:15PM +0300, ville.syrjala@linux.intel.com wrote:
>> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>> 
>> On CHV the display DDC pins may be muxed to an alternate function if
>> there's no need for DDC on a specific port, which is the case for eDP
>> ports since there's no way to plug in a DP++ HDMI dongle.
>> 
>> This causes problems when trying to determine if the port is present
>> since the the DP_DETECTED bit is the latched state of the DDC SDA pin
>> at boot. If the DDC pins are muxed to an alternate function the bit
>> may indicate that the port isn't present.
>> 
>> To work around this look at the VBT as well as the DP_DETECTED bit
>> to determine if we should attempt registering an eDP port. Do this
>> only for ports B and C since port D doesn't support eDP (no PPS/BLC).
>> 
>> In theory someone could also wire up a normal DP port w/o DDC lines.
>> That would just mean that simple DP++ HDMI dongles wouldn't work
>> on such a port. With this change we would still fail to register
>> such DP ports. But let's hope no one wires their board in such a way,
>> and if they do we can extend the VBT checks to cover normal DP ports
>> as well.
>> 
>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=84265
>> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>

Pushed to drm-intel-next-fixes, thanks for the patch and review.

BR,
Jani.

>
> -- 
> Damien
>
>> ---
>>  drivers/gpu/drm/i915/intel_display.c | 33 +++++++++++++++++++++------------
>>  1 file changed, 21 insertions(+), 12 deletions(-)
>> 
>> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
>> index b5476dc..d6fc469 100644
>> --- a/drivers/gpu/drm/i915/intel_display.c
>> +++ b/drivers/gpu/drm/i915/intel_display.c
>> @@ -12280,27 +12280,36 @@ static void intel_setup_outputs(struct drm_device *dev)
>>  		if (I915_READ(PCH_DP_D) & DP_DETECTED)
>>  			intel_dp_init(dev, PCH_DP_D, PORT_D);
>>  	} else if (IS_VALLEYVIEW(dev)) {
>> -		if (I915_READ(VLV_DISPLAY_BASE + GEN4_HDMIB) & SDVO_DETECTED) {
>> +		/*
>> +		 * The DP_DETECTED bit is the latched state of the DDC
>> +		 * SDA pin at boot. However since eDP doesn't require DDC
>> +		 * (no way to plug in a DP->HDMI dongle) the DDC pins for
>> +		 * eDP ports may have been muxed to an alternate function.
>> +		 * Thus we can't rely on the DP_DETECTED bit alone to detect
>> +		 * eDP ports. Consult the VBT as well as DP_DETECTED to
>> +		 * detect eDP ports.
>> +		 */
>> +		if (I915_READ(VLV_DISPLAY_BASE + GEN4_HDMIB) & SDVO_DETECTED)
>>  			intel_hdmi_init(dev, VLV_DISPLAY_BASE + GEN4_HDMIB,
>>  					PORT_B);
>> -			if (I915_READ(VLV_DISPLAY_BASE + DP_B) & DP_DETECTED)
>> -				intel_dp_init(dev, VLV_DISPLAY_BASE + DP_B, PORT_B);
>> -		}
>> +		if (I915_READ(VLV_DISPLAY_BASE + DP_B) & DP_DETECTED ||
>> +		    intel_dp_is_edp(dev, PORT_B))
>> +			intel_dp_init(dev, VLV_DISPLAY_BASE + DP_B, PORT_B);
>>  
>> -		if (I915_READ(VLV_DISPLAY_BASE + GEN4_HDMIC) & SDVO_DETECTED) {
>> +		if (I915_READ(VLV_DISPLAY_BASE + GEN4_HDMIC) & SDVO_DETECTED)
>>  			intel_hdmi_init(dev, VLV_DISPLAY_BASE + GEN4_HDMIC,
>>  					PORT_C);
>> -			if (I915_READ(VLV_DISPLAY_BASE + DP_C) & DP_DETECTED)
>> -				intel_dp_init(dev, VLV_DISPLAY_BASE + DP_C, PORT_C);
>> -		}
>> +		if (I915_READ(VLV_DISPLAY_BASE + DP_C) & DP_DETECTED ||
>> +		    intel_dp_is_edp(dev, PORT_C))
>> +			intel_dp_init(dev, VLV_DISPLAY_BASE + DP_C, PORT_C);
>>  
>>  		if (IS_CHERRYVIEW(dev)) {
>> -			if (I915_READ(VLV_DISPLAY_BASE + CHV_HDMID) & SDVO_DETECTED) {
>> +			if (I915_READ(VLV_DISPLAY_BASE + CHV_HDMID) & SDVO_DETECTED)
>>  				intel_hdmi_init(dev, VLV_DISPLAY_BASE + CHV_HDMID,
>>  						PORT_D);
>> -				if (I915_READ(VLV_DISPLAY_BASE + DP_D) & DP_DETECTED)
>> -					intel_dp_init(dev, VLV_DISPLAY_BASE + DP_D, PORT_D);
>> -			}
>> +			/* eDP not supported on port D, so don't check VBT */
>> +			if (I915_READ(VLV_DISPLAY_BASE + DP_D) & DP_DETECTED)
>> +				intel_dp_init(dev, VLV_DISPLAY_BASE + DP_D, PORT_D);
>>  		}
>>  
>>  		intel_dsi_init(dev);
>> -- 
>> 2.0.4
>> 
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-- 
Jani Nikula, Intel Open Source Technology Center
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