Re: [Intel-gfx] [PATCH v6 2/7] drm/i915: update the QGV point frequency calculations

[Jani Nikula <jani.nikula@linux.intel.com>]

On Tue, 23 May 2023, Vinod Govindapillai <vinod.govindapillai@intel.com> wrote:
> From MTL onwwards, pcode locks the QGV point based on peak BW of
> the intended QGV point passed by the driver. So the peak BW
> calculation must match the value expected by the pcode. Update
> the calculations as per the Bspec.
>
> v2: use DIV_ROUND_* macro for the calculations (Ville)
>
> Bspec: 64636
>
> Signed-off-by: Vinod Govindapillai <vinod.govindapillai@intel.com>
> Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_bw.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_bw.c b/drivers/gpu/drm/i915/display/intel_bw.c
> index ab405c48ca3a..c8075a37c3ab 100644
> --- a/drivers/gpu/drm/i915/display/intel_bw.c
> +++ b/drivers/gpu/drm/i915/display/intel_bw.c
> @@ -182,7 +182,7 @@ static int mtl_read_qgv_point_info(struct drm_i915_private *dev_priv,
>  	val2 = intel_uncore_read(&dev_priv->uncore,
>  				 MTL_MEM_SS_INFO_QGV_POINT_HIGH(point));
>  	dclk = REG_FIELD_GET(MTL_DCLK_MASK, val);
> -	sp->dclk = DIV_ROUND_UP((16667 * dclk), 1000);
> +	sp->dclk = DIV_ROUND_CLOSEST(16667 * dclk + 500, 1000);

What's with the +500 there?

BR,
Jani.


>  	sp->t_rp = REG_FIELD_GET(MTL_TRP_MASK, val);
>  	sp->t_rcd = REG_FIELD_GET(MTL_TRCD_MASK, val);

-- 
Jani Nikula, Intel Open Source Graphics Center