Re: [PATCH v2 3/3] drm/i915/icl: Work around broken VBTs for port F detection

[Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>]

On Thu, 2018-12-20 at 17:52 +0200, Imre Deak wrote:
> VBT may include incorrect information about the presence of port F.
> Work
> around this on SKUs where we know the port is not present.

If we cannot trust the data in VBT, can we not test for the absence of
port-F by enabling the powerwell and checking for a timeout? Or at
least mark up a non-existent port after the first timeout so that we
don't keep probing it.  

This patch is an improvement over checking the VBT for all ports, so
Reviewed-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>

> 
> v2:
> - Fix IS_ICL_WITH_PORT_F, so it's useable from any context.
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=108915
> Cc: Mika Kahola <mika.kahola@intel.com>
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Signed-off-by: Imre Deak <imre.deak@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_drv.h      | 2 ++
>  drivers/gpu/drm/i915/intel_display.c | 4 +++-
>  2 files changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.h
> b/drivers/gpu/drm/i915/i915_drv.h
> index 815db160b966..e45cda9d9555 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -2317,6 +2317,8 @@ intel_info(const struct drm_i915_private
> *dev_priv)
>  				 (dev_priv)->info.gt == 3)
>  #define IS_CNL_WITH_PORT_F(dev_priv)   (IS_CANNONLAKE(dev_priv) && \
>  					(INTEL_DEVID(dev_priv) &
> 0x0004) == 0x0004)
> +#define IS_ICL_WITH_PORT_F(dev_priv)   (IS_ICELAKE(dev_priv) && \
> +					INTEL_DEVID(dev_priv) !=
> 0x8A51)
>  
>  #define IS_ALPHA_SUPPORT(intel_info) ((intel_info)-
> >is_alpha_support)
>  
> diff --git a/drivers/gpu/drm/i915/intel_display.c
> b/drivers/gpu/drm/i915/intel_display.c
> index 2b81da068010..bd7fdaf7e093 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -14276,8 +14276,10 @@ static void intel_setup_outputs(struct
> drm_i915_private *dev_priv)
>  		/*
>  		 * On some ICL SKUs port F is not present. No strap
> bits for
>  		 * this, so rely on VBT.
> +		 * Work around broken VBTs on SKUs known to have no
> port F.
>  		 */
> -		if (intel_bios_is_port_present(dev_priv, PORT_F))
> +		if (IS_ICL_WITH_PORT_F(dev_priv) &&
> +		    intel_bios_is_port_present(dev_priv, PORT_F))
>  			intel_ddi_init(dev_priv, PORT_F);
>  
>  		icl_dsi_init(dev_priv);

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