[RFC] drm/i915/display: Update vtotal math to address 32b build

[Golani, Mitulkumar Ajitkumar]

Hi @De Marchi, Lucas

> -----Original Message-----
> From: De Marchi, Lucas <lucas.demarchi at intel.com>
> Sent: Wednesday, June 12, 2024 10:02 AM
> To: Golani, Mitulkumar Ajitkumar <mitulkumar.ajitkumar.golani at intel.com>
> Cc: intel-xe at lists.freedesktop.org; intel-gfx at lists.freedesktop.org
> Subject: Re: [RFC] drm/i915/display: Update vtotal math to address 32b build
> 
> On Wed, Jun 12, 2024 at 12:02:08AM GMT, Mitul Golani wrote:
> >Fix few divisions which may not work on 32b builds.
> >
> >Use DIV_ROUND_UP, with that expecting deviate params from +/- 1
> >accuracy in value.
> >
> >Fixes: 1676ecd303ac ("drm/i915: Compute CMRR and calculate vtotal")
> >Signed-off-by: Mitul Golani <mitulkumar.ajitkumar.golani at intel.com>
> >---
> > drivers/gpu/drm/i915/display/intel_vrr.c | 10 ++++++----
> > 1 file changed, 6 insertions(+), 4 deletions(-)
> >
> >diff --git a/drivers/gpu/drm/i915/display/intel_vrr.c
> >b/drivers/gpu/drm/i915/display/intel_vrr.c
> >index 05f67dc9d98d..5112961f6964 100644
> >--- a/drivers/gpu/drm/i915/display/intel_vrr.c
> >+++ b/drivers/gpu/drm/i915/display/intel_vrr.c
> >@@ -122,10 +122,11 @@ is_cmrr_frac_required(struct intel_crtc_state
> >*crtc_state)
> >
> > 	actual_refresh_k =
> > 		drm_mode_vrefresh(adjusted_mode) *
> FIXED_POINT_PRECISION;
> >-	pixel_clock_per_line =
> >-		adjusted_mode->crtc_clock * 1000 / adjusted_mode-
> >crtc_htotal;
> >+	pixel_clock_per_line = DIV_ROUND_UP(adjusted_mode->crtc_clock *
> 1000,
> >+					    adjusted_mode->crtc_htotal);
> > 	calculated_refresh_k =
> >-		pixel_clock_per_line * FIXED_POINT_PRECISION /
> adjusted_mode->crtc_vtotal;
> >+		DIV_ROUND_UP(pixel_clock_per_line *
> FIXED_POINT_PRECISION,
> >+			     adjusted_mode->crtc_vtotal);
> >
> > 	if ((actual_refresh_k - calculated_refresh_k) <
> CMRR_PRECISION_TOLERANCE)
> > 		return false;
> >@@ -149,7 +150,8 @@ cmrr_get_vtotal(struct intel_crtc_state
> >*crtc_state, bool video_mode_required)
> >
> > 	crtc_state->cmrr.cmrr_n =
> > 		desired_refresh_rate * adjusted_mode->crtc_htotal *
> multiplier_n;
> >-	vtotal = (adjusted_mode->crtc_clock * 1000 * multiplier_n) /
> crtc_state->cmrr.cmrr_n;
> >+	vtotal = DIV_ROUND_UP(adjusted_mode->crtc_clock * 1000 *
> multiplier_n,
> >+			      crtc_state->cmrr.cmrr_n);
> 
> to fix the 32b build you need to build with DIV_ROUND_UP_ULL ().
> 

Thanks, tried with DIV_ROUND_UP_ULL, build is passing on 32b config as well. Change is floated for review.

Regards,
Mitul

> Lucas De Marchi
> 
> > 	adjusted_pixel_rate = adjusted_mode->crtc_clock * 1000 *
> multiplier_m;
> > 	crtc_state->cmrr.cmrr_m = do_div(adjusted_pixel_rate,
> > crtc_state->cmrr.cmrr_n);
> >
> >--
> >2.45.2
> >