linux-kernel - Re: [PATCH v5 4/4] drm/i915/gen9_bc: Add W/A for missing STRAP config on TGP PCH + CML combos

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Date:   Wed, 10 Feb 2021 22:23:58 -0500
From:   Rodrigo Vivi <rodrigo.vivi@...el.com>
To:     Lyude Paul <lyude@...hat.com>
Cc:     intel-gfx@...ts.freedesktop.org,
        Karthik B S <karthik.b.s@...el.com>,
        David Airlie <airlied@...ux.ie>,
        Pankaj Bharadiya <pankaj.laxminarayan.bharadiya@...el.com>,
        "open list:DRM DRIVERS" <dri-devel@...ts.freedesktop.org>,
        open list <linux-kernel@...r.kernel.org>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Manasi Navare <manasi.d.navare@...el.com>,
        Yijun Shen <Yijun.Shen@...l.com>,
        José Roberto de Souza 
        <jose.souza@...el.com>, Dave Airlie <airlied@...hat.com>,
        Tejas Upadhyay <tejaskumarx.surendrakumar.upadhyay@...el.com>
Subject: Re: [PATCH v5 4/4] drm/i915/gen9_bc: Add W/A for missing STRAP
 config on TGP PCH + CML combos

On Tue, Feb 09, 2021 at 04:28:31PM -0500, Lyude Paul wrote:
> Apparently the new gen9_bc platforms that Intel has introduced don't
> provide us with a STRAP config register to read from for initializing DDI
> B, C, and D detection. So, workaround this by hard-coding our strap config
> in intel_setup_outputs().
> 
> Changes since v4:
> * Split this into it's own commit
> 
> Cc: Matt Roper <matthew.d.roper@...el.com>
> Cc: Jani Nikula <jani.nikula@...ux.intel.com>
> Cc: Ville Syrjala <ville.syrjala@...ux.intel.com>
> [originally from Tejas's work]
> Signed-off-by: Tejas Upadhyay <tejaskumarx.surendrakumar.upadhyay@...el.com>
> Signed-off-by: Lyude Paul <lyude@...hat.com>
> ---
>  drivers/gpu/drm/i915/display/intel_display.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> index beed08c00b6c..4dee37f8659d 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -11943,7 +11943,14 @@ static void intel_setup_outputs(struct drm_i915_private *dev_priv)
>  
>  		/* DDI B, C, D, and F detection is indicated by the SFUSE_STRAP
>  		 * register */
> -		found = intel_de_read(dev_priv, SFUSE_STRAP);
> +		if (HAS_PCH_TGP(dev_priv)) {
> +			/* W/A due to lack of STRAP config on TGP PCH*/
> +			found = (SFUSE_STRAP_DDIB_DETECTED |
> +				 SFUSE_STRAP_DDIC_DETECTED |
> +				 SFUSE_STRAP_DDID_DETECTED);

we have somewhere in this function these forced fuse straps for gen9 platform...
don't we have a ways to combine them?

Afterall, the reason that we need these forced bits is
because it is a gen9, not because it is a TGP...

> +		} else {
> +			found = intel_de_read(dev_priv, SFUSE_STRAP);
> +		}
>  
>  		if (found & SFUSE_STRAP_DDIB_DETECTED)
>  			intel_ddi_init(dev_priv, PORT_B);
> -- 
> 2.29.2
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@...ts.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

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