Hi @Nathan Chancellor, Yes, with do_div, we are expecting the remainder value. Regarding the warning related to the adjusted_pixel_rate type cast, I haven't been able to reproduce this locally, possibly due to differences in the cross-compiler. We should consider typecasting adjusted_pixel_rate or treating it as unsigned ? Adding @Nikula, Jani to suggest. Regards, Mitul > -----Original Message----- > From: Nathan Chancellor <nathan@xxxxxxxxxx> > Sent: Wednesday, June 19, 2024 11:56 PM > To: Golani, Mitulkumar Ajitkumar <mitulkumar.ajitkumar.golani@xxxxxxxxx> > Cc: intel-gfx@xxxxxxxxxxxxxxxxxxxxx; Nautiyal, Ankit K > <ankit.k.nautiyal@xxxxxxxxx>; intel-xe@xxxxxxxxxxxxxxxxxxxxx > Subject: Re: [PATCH v16 9/9] drm/i915: Compute CMRR and calculate vtotal > > On Wed, Jun 19, 2024 at 06:10:34PM +0000, Golani, Mitulkumar Ajitkumar > wrote: > > Hi @Nathan Chancellor > > > > Probably fix is merged in drm-intel-next related patch: > > https://patchwork.freedesktop.org/series/134860/ > > > > Can you please check and suggest if this patch is merged ? > > This is still reproducible at commit 851de367dede ("drm/i915: Enable > plane/pipeDMC ATS fault interrupts on mtl") in drm-intel-next, which includes > that change as commit e2dc7cb72b25 ("drm/i915/display: Update calculation > to avoid overflow"). The issue is the dividend in do_div() is required to be an > unsigned 64-bit type but you used a signed type. > Updating adjusted_pixel_rate to be a u64 should resolve the issue and match > the return type of mul_u32_u32(). I just wasn't sure if that was the only fix > this code would need, as do_div() is not typically used with an assignment. > > Cheers, > Nathan > > > > -----Original Message----- > > > From: Nathan Chancellor <nathan@xxxxxxxxxx> > > > Sent: Wednesday, June 19, 2024 9:12 PM > > > To: Golani, Mitulkumar Ajitkumar > > > <mitulkumar.ajitkumar.golani@xxxxxxxxx> > > > Cc: intel-gfx@xxxxxxxxxxxxxxxxxxxxx; Nautiyal, Ankit K > > > <ankit.k.nautiyal@xxxxxxxxx>; intel-xe@xxxxxxxxxxxxxxxxxxxxx > > > Subject: Re: [PATCH v16 9/9] drm/i915: Compute CMRR and calculate > > > vtotal > > > > > > Hi Mitul, > > > > > > On Mon, Jun 10, 2024 at 12:52:02PM +0530, Mitul Golani wrote: > > > ... > > > > diff --git a/drivers/gpu/drm/i915/display/intel_vrr.c > > > > b/drivers/gpu/drm/i915/display/intel_vrr.c > > > > index 4ad99a54aa83..05f67dc9d98d 100644 > > > > --- a/drivers/gpu/drm/i915/display/intel_vrr.c > > > > +++ b/drivers/gpu/drm/i915/display/intel_vrr.c > > > > @@ -12,6 +12,9 @@ > > > > #include "intel_vrr_regs.h" > > > > #include "intel_dp.h" > > > > > > > > +#define FIXED_POINT_PRECISION 100 > > > > +#define CMRR_PRECISION_TOLERANCE 10 > > > > + > > > > bool intel_vrr_is_capable(struct intel_connector *connector) { > > > > const struct drm_display_info *info = > > > > &connector->base.display_info; @@ -107,6 +110,52 @@ int > > > > intel_vrr_vmax_vblank_start(const struct > > > intel_crtc_state *crtc_state) > > > > return crtc_state->vrr.vmax - > > > > intel_vrr_vblank_exit_length(crtc_state); > > > > } > > > > > > > > +static bool > > > > +is_cmrr_frac_required(struct intel_crtc_state *crtc_state) { > > > > + int calculated_refresh_k, actual_refresh_k, pixel_clock_per_line; > > > > + struct drm_display_mode *adjusted_mode = &crtc_state- > > > >hw.adjusted_mode; > > > > + struct drm_i915_private *i915 = > > > > +to_i915(crtc_state->uapi.crtc->dev); > > > > + > > > > + if (!HAS_CMRR(i915)) > > > > + return false; > > > > + > > > > + actual_refresh_k = > > > > + drm_mode_vrefresh(adjusted_mode) * > > > FIXED_POINT_PRECISION; > > > > + pixel_clock_per_line = > > > > + adjusted_mode->crtc_clock * 1000 / adjusted_mode- > > > >crtc_htotal; > > > > + calculated_refresh_k = > > > > + pixel_clock_per_line * FIXED_POINT_PRECISION / > > > > +adjusted_mode->crtc_vtotal; > > > > + > > > > + if ((actual_refresh_k - calculated_refresh_k) < > > > CMRR_PRECISION_TOLERANCE) > > > > + return false; > > > > + > > > > + return true; > > > > +} > > > > + > > > > +static unsigned int > > > > +cmrr_get_vtotal(struct intel_crtc_state *crtc_state, bool > > > > +video_mode_required) { > > > > + int multiplier_m = 1, multiplier_n = 1, vtotal, desired_refresh_rate; > > > > + long long adjusted_pixel_rate; > > > > + struct drm_display_mode *adjusted_mode = > > > > +&crtc_state->hw.adjusted_mode; > > > > + > > > > + desired_refresh_rate = drm_mode_vrefresh(adjusted_mode); > > > > + > > > > + if (video_mode_required) { > > > > + multiplier_m = 1001; > > > > + multiplier_n = 1000; > > > > + } > > > > + > > > > + 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; > > > > + 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); > > > > + > > > > + return vtotal; > > > > +} > > > > > > This change is now in -next as commit 1676ecd303ac ("drm/i915: > > > Compute CMRR and calculate vtotal"), where it breaks the xe build > > > for 32-bit platforms > > > with: > > > > > > $ make -skj"$(nproc)" ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- > > > allmodconfig drivers/gpu/drm/xe/i915-display/intel_vrr.o > > > In file included from arch/arm/include/asm/div64.h:107, > > > from include/linux/math.h:6, > > > from include/linux/kernel.h:27, > > > from include/linux/cpumask.h:11, > > > from include/linux/smp.h:13, > > > from include/linux/lockdep.h:14, > > > from include/linux/spinlock.h:63, > > > from include/linux/kref.h:16, > > > from include/drm/drm_device.h:5, > > > from include/drm/drm_drv.h:35, > > > from drivers/gpu/drm/xe/compat-i915-headers/i915_drv.h:13, > > > from drivers/gpu/drm/i915/display/intel_vrr.c:7: > > > drivers/gpu/drm/i915/display/intel_vrr.c: In function 'cmrr_get_vtotal': > > > include/asm-generic/div64.h:222:35: error: comparison of distinct > > > pointer types lacks a cast [-Werror] > > > 222 | (void)(((typeof((n)) *)0) == ((uint64_t *)0)); \ > > > | ^~ > > > drivers/gpu/drm/i915/display/intel_vrr.c:155:35: note: in > > > expansion of macro 'do_div' > > > 155 | crtc_state->cmrr.cmrr_m = do_div(adjusted_pixel_rate, > crtc_state- > > > >cmrr.cmrr_n); > > > | ^~~~~~ > > > cc1: all warnings being treated as errors > > > > > > Also, is do_div() correct here? It is different from the other > > > div_() macros in that the "return value" is the remainder, not the result of > the division. > > > > > > Cheers, > > > Nathan
