[Intel-gfx] [PATCH] drm/i915/bxt: Reversed polarity of PORT_PLL_REF_SEL bit

[Imre Deak]

On Tue, 2016-03-15 at 16:37 -0700, Dongwon Kim wrote:
> For BXT, Polarity of PORT_PLL_REF_SEL is reversed in
> its description in Bspec. This bit should be set for
> "Non-SSC".

Thanks for the patch.

In the future please also mention where the change originates from, in
this case it is a recent update to the specification (which in turn is
based on an internal report of an HDMI HW problem). Looking at that
internal report (HSD) it says it only affects BXT-P but not BXT-T, so
do we know that the meaning of the bit is inverted on both?

Adding Art for more info.

--Imre

> Signed-off-by: Dongwon Kim <dongwon.kim at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dpll_mgr.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dpll_mgr.c
> b/drivers/gpu/drm/i915/intel_dpll_mgr.c
> index 4b636c4..d55b308 100644
> --- a/drivers/gpu/drm/i915/intel_dpll_mgr.c
> +++ b/drivers/gpu/drm/i915/intel_dpll_mgr.c
> @@ -1285,7 +1285,7 @@ static void bxt_ddi_pll_enable(struct
> drm_i915_private *dev_priv,
>  	enum port port = (enum port)pll->id;	/* 1:1 port->PLL 
> mapping */
>  
>  	temp = I915_READ(BXT_PORT_PLL_ENABLE(port));
> -	temp &= ~PORT_PLL_REF_SEL;
> +	temp |= PORT_PLL_REF_SEL;
>  	/* Non-SSC reference */
>  	I915_WRITE(BXT_PORT_PLL_ENABLE(port), temp);
>