Re: [PATCH v2] drm/i915/skl: Add warn about unsupported CDCLK rates

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Fri, Jun 08, 2018 at 05:00:02PM +0300, Imre Deak wrote:
> While checking workarounds related to the CDCLK PLL, I noticed that the
> DMC firmware bits for WA#1183 are missing for SKL. After that I
> clarified with HW people that it's not needed on SKL, since it doesn't
> support eDP1.4 which would be the only thing requiring the problematic
> CDCLK clock rates. So in theory we shouldn't ever choose these
> frequencies, but add an assert in any case for catching such cases and
> for documentation.
> 
> v2:
> - Move the check to skl_set_cdclk and warn whenever using the
>   corresponding VCO freq. (Ville)
> 
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Signed-off-by: Imre Deak <imre.deak@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_cdclk.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_cdclk.c b/drivers/gpu/drm/i915/intel_cdclk.c
> index 704ddb4d3ca7..a1e9434698b9 100644
> --- a/drivers/gpu/drm/i915/intel_cdclk.c
> +++ b/drivers/gpu/drm/i915/intel_cdclk.c
> @@ -991,6 +991,16 @@ static void skl_set_cdclk(struct drm_i915_private *dev_priv,
>  	u32 freq_select, cdclk_ctl;
>  	int ret;
>  
> +	/*
> +	 * Based on WA#1183 CDCLK rates 308 and 617MHz CDCLK rates are
> +	 * unsupported on SKL. In theory this should never happen since only
> +	 * the eDP1.4 2.16 and 4.32Gbps rates require it, but eDP1.4 is not
> +	 * supported on SKL either, see the above WA. WARN whenever trying to
> +	 * use the corresponding VCO freq as that always leads to using the
> +	 * minimum 308MHz CDCLK.
> +	 */
> +	WARN_ON_ONCE(vco == 8640000);

Needs IS_SKYLAKE()

with that
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

> +
>  	mutex_lock(&dev_priv->pcu_lock);
>  	ret = skl_pcode_request(dev_priv, SKL_PCODE_CDCLK_CONTROL,
>  				SKL_CDCLK_PREPARE_FOR_CHANGE,
> -- 
> 2.13.2

-- 
Ville Syrjälä
Intel
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx