On Tue, 23 May 2023, "Govindapillai, Vinod" <vinod.govindapillai@xxxxxxxxx> wrote: > On Tue, 2023-05-23 at 12:01 +0300, Jani Nikula wrote: >> On Tue, 23 May 2023, Vinod Govindapillai <vinod.govindapillai@xxxxxxxxx> 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@xxxxxxxxx> >> > Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@xxxxxxxxx> >> > --- >> > 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? > > This is what pcode expects. Somehow pcode use this formula and we have to exactly match this. Got > this confirmed from Art. I'm guessing all it really means is to round to closest, and they specified it like that instead of saying "round to closest". Essentially (x + (div/2)) / div is what DIV_ROUND_CLOSEST() does. It's odd to do it *twice*, and surely not what they expect. BR, Jani. > > BR > Vinod > >> >> 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
