Please check the DRAM configuration for the systems that fail. The higher latency is more likely with higher tRFC which is mainly found with 8 Gbit components.
>-----Original Message----- >From: daniel.vet...@ffwll.ch [mailto:daniel.vet...@ffwll.ch] On Behalf Of >Daniel Vetter >Sent: Friday, March 21, 2014 3:19 AM >To: Nikula, Jani; Runyan, Arthur J; Syrjala, Ville >Cc: intel-gfx >Subject: Re: [Intel-gfx] [PATCH] drm/i915: Increase WM memory latency values >on SNB with >high pixel clock > >On Fri, Mar 21, 2014 at 11:00:48AM +0200, Jani Nikula wrote: >> From: Ville Syrjälä <ville.syrj...@linux.intel.com> >> >> On SNB the BIOS provided WM memory latency values seem insufficient to >> handle high resolution displays. >> >> In this particular case the display mode was a 2560x1440@60Hz, which >> makes the pixel clock 241.5 MHz. It was empirically found that a memory >> latency value if 1.2 usec is enough to avoid underruns, whereas the BIOS >> provided value of 0.7 usec was clearly too low. Incidentally 1.2 usec >> is what the typical BIOS provided values are on IVB systems. >> >> Increase the WM memory latency values to 1.2 usec when encountering a >> display mode with pixel clock exceeding 225 MHz. 225 MHz was chosen as >> the threshold simply because that's the documented limit of SNB with >> HDMI, so one might surmise that the hardware may have been tested up >> to that frequency. In theory the latency shouldn't depend on the pixel >> clock at all. So it may be that we should just increase the latency >> values across the board for all SNB systems. But for now I'm inclined >> to limit this quirk to only those cases that are proven to need it, >> as doing otherwise might cause some increase in power consumption for >> everyone. >> >> Cc: Robert N <crsh...@gmail.com> >> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=70254 >> Signed-off-by: Ville Syrjälä <ville.syrj...@linux.intel.com> > >I think we should just unconditionally increase the memory latency. ivb >has a rather similar memory subsystem compared to snb, so just increasing >it always to this limits sounds ok. For lower resolutions we might simply >get away because there's more excess bandwidth available. > >Maybe Art can shed some light on this. >-Daniel > >> >> --- >> >> I'm just relaying the patch from bugzilla to the list as it seems to fix >> the bug. Don't ask me anything about it. >> >> BR, >> Jani. >> --- >> drivers/gpu/drm/i915/intel_display.c | 10 ++++++++++ >> drivers/gpu/drm/i915/intel_drv.h | 1 + >> drivers/gpu/drm/i915/intel_pm.c | 33 >> +++++++++++++++++++++++++++++++++ >> 3 files changed, 44 insertions(+) >> >> diff --git a/drivers/gpu/drm/i915/intel_display.c >> b/drivers/gpu/drm/i915/intel_display.c >> index 0b19afdfbaa7..b0ac92d8f461 100644 >> --- a/drivers/gpu/drm/i915/intel_display.c >> +++ b/drivers/gpu/drm/i915/intel_display.c >> @@ -9933,6 +9933,16 @@ static int __intel_set_mode(struct drm_crtc *crtc, >> */ >> drm_calc_timestamping_constants(crtc, >> &pipe_config->adjusted_mode); >> + >> + >> + /* >> + * The BIOS provided WM memory latency values are often >> + * inadequate for high resolution displays. Adjust them. >> + * >> + * FIXME not sure 225MHz is a good threshold. >> + */ >> + if (IS_GEN6(dev) && pipe_config->adjusted_mode.crtc_clock > 225000) >> + snb_wm_latency_quirk(dev); >> } >> >> /* Only after disabling all output pipelines that will be changed can we >> diff --git a/drivers/gpu/drm/i915/intel_drv.h >> b/drivers/gpu/drm/i915/intel_drv.h >> index 60ffad376390..b1d631c9dfa5 100644 >> --- a/drivers/gpu/drm/i915/intel_drv.h >> +++ b/drivers/gpu/drm/i915/intel_drv.h >> @@ -903,6 +903,7 @@ void intel_runtime_pm_put(struct drm_i915_private >> *dev_priv); >> void intel_init_runtime_pm(struct drm_i915_private *dev_priv); >> void intel_fini_runtime_pm(struct drm_i915_private *dev_priv); >> void ilk_wm_get_hw_state(struct drm_device *dev); >> +void snb_wm_latency_quirk(struct drm_device *dev); >> >> >> /* intel_sdvo.c */ >> diff --git a/drivers/gpu/drm/i915/intel_pm.c >> b/drivers/gpu/drm/i915/intel_pm.c >> index 39f3238bf1c3..226750452637 100644 >> --- a/drivers/gpu/drm/i915/intel_pm.c >> +++ b/drivers/gpu/drm/i915/intel_pm.c >> @@ -2104,6 +2104,39 @@ static void ilk_setup_wm_latency(struct drm_device >> *dev) >> intel_print_wm_latency(dev, "Cursor", dev_priv->wm.cur_latency); >> } >> >> +static bool ilk_increase_wm_latency(struct drm_i915_private *dev_priv, >> + uint16_t wm[5], uint16_t min) >> +{ >> + int level, max_level = ilk_wm_max_level(dev_priv->dev); >> + >> + if (wm[0] >= min) >> + return false; >> + >> + wm[0] = max(wm[0], min); >> + for (level = 1; level <= max_level; level++) >> + wm[level] = max_t(uint16_t, wm[level], DIV_ROUND_UP(min, 5)); >> + >> + return true; >> +} >> + >> +void snb_wm_latency_quirk(struct drm_device *dev) >> +{ >> + struct drm_i915_private *dev_priv = dev->dev_private; >> + bool changed; >> + >> + changed = ilk_increase_wm_latency(dev_priv, dev_priv->wm.pri_latency, 12) | >> + ilk_increase_wm_latency(dev_priv, dev_priv->wm.spr_latency, 12) | >> + ilk_increase_wm_latency(dev_priv, dev_priv->wm.cur_latency, 12); >> + >> + if (!changed) >> + return; >> + >> + DRM_DEBUG_KMS("WM latency values increased due to high pixel clock\n"); >> + intel_print_wm_latency(dev, "Primary", dev_priv->wm.pri_latency); >> + intel_print_wm_latency(dev, "Sprite", dev_priv->wm.spr_latency); >> + intel_print_wm_latency(dev, "Cursor", dev_priv->wm.cur_latency); >> +} >> + >> static void ilk_compute_wm_parameters(struct drm_crtc *crtc, >> struct ilk_pipe_wm_parameters *p, >> struct intel_wm_config *config) >> -- >> 1.7.9.5 >> >> _______________________________________________ >> Intel-gfx mailing list >> Intel-gfx@lists.freedesktop.org >> http://lists.freedesktop.org/mailman/listinfo/intel-gfx > >-- >Daniel Vetter >Software Engineer, Intel Corporation >+41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/intel-gfx
