[Intel-gfx] [PATCH 03/10] drm/i915: Check VBT for CRT port presence on HSW/BDW

[Chris Wilson]

On Tue, Dec 01, 2015 at 03:08:34PM +0200, ville.syrjala at linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> Unfortunatey there appear to quite a few HSW/BDW machines (eg.
> NUCs, Brix Pro) in the wild with LPT/WPT-H but non-working FDI.
> FDI training fails every single time on these machines. Dunno,
> maybe they just didn't bother wiring it up or something?
> 
> Unfortunately all the fuse bits and whatnot are telling us that
> the CRT connector is present. And so what we get from this is tons
> of false positives from the CI systems due to VGA connector forcing.
> 
> I've not found any way to detect this purely from hardware, so we
> have to resort to looking at the VBT int_crt_support bit. We used
> to check this bit on all platforms, but that broke all the old
> machines, so the check was then restricted to VLV only in
> commit 84b4e042c470 ("drm/i915: only apply crt_present check on VLV")
> 
> Considering HSW and VLV VBT probably got defined around the same time,
> it should be reasonably safe to assume that the bits is sane for
> HSW/BDW as well. At least I have one copy of some VBT spec here that
> says it's meant for both VLV and HSW, and it knows about the bit
> (lists it being valid from version 155 onwards). Also I have two
> HSW desktop machines with actual CRT ports and both have
> int_crt_support==1 in their VBTs.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_display.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index e80387dd6582..29ea4c458ab3 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -14263,7 +14263,7 @@ static bool intel_crt_present(struct drm_device *dev)
>  	if (HAS_DDI(dev) && I915_READ(DDI_BUF_CTL(PORT_A)) & DDI_A_4_LANES)
>  		return false;
>  
> -	if (IS_VALLEYVIEW(dev) && !dev_priv->vbt.int_crt_support)
> +	if ((HAS_DDI(dev) || IS_VALLEYVIEW(dev)) && !dev_priv->vbt.int_crt_support)

Would it not be better to move this knowledge to vbt if it is version
dependent?

	vbt.int_crtc_support = (UNKNOWN, NOT_PRESENT, PRESENT)

then

	if (dev_priv->vbt.int_crt_support == NOT_PRESENT)
>  		return false;
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre