> -----Original Message----- > From: Jani Nikula [mailto:jani.nikula@xxxxxxxxxxxxxxx] > Sent: Friday, November 20, 2015 3:47 PM > To: Kahola, Mika; intel-gfx@xxxxxxxxxxxxxxxxxxxxx > Subject: Re: [PATCH] drm/i915: Make DP fast link training a > module parameter > > On Fri, 20 Nov 2015, Mika Kahola <mika.kahola@xxxxxxxxx> wrote: > > There is a bug report > > > > https://bugs.freedesktop.org/show_bug.cgi?id=91393 > > > > indicating that there are panels that do not support link training > > starting with non-zero voltage swing and pre-emphasis values. > > > > This patch proposes to make this fast link training feature as one > > module parameter. To take more conservative approach this feature is > > disabled by default. > > Please let's not add any more of these. If we can't make this work > automatically (we should still keep trying) I'd say we remove it. > > Adding features behind module parameters means that most people will > never use them. Theoretically it doubles our testing efforts because we > would have to test with the feature on and off; in practise that won't happen > and only the default will be tested (because we already have so many > features behind parameters). The code bitrots and breaks even for the > platforms on which it did work originally. Then there are a minority of people > who will enable all possible knobs they read about on forums and think will > improve performance or power savings or something, and report bugs when > they fail. > > IMO there's just too much effort for too little gain if we can't enable this. I > just wish we would have been able to block more of the module parameters > earlier... > The idea that I had in mind was to keep this feature as selectable item until we get this working for all panel combinations. That said, I consider this would have been only a first aid to the problem. Anyway, back to the drawing board... Cheers, Mika > > BR, > Jani. > > > > > > Signed-off-by: Mika Kahola <mika.kahola@xxxxxxxxx> > > --- > > drivers/gpu/drm/i915/i915_drv.h | 1 + > > drivers/gpu/drm/i915/i915_params.c | 4 ++++ > > drivers/gpu/drm/i915/intel_dp_link_training.c | 11 ++++++++++- > > 3 files changed, 15 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/gpu/drm/i915/i915_drv.h > > b/drivers/gpu/drm/i915/i915_drv.h index a47e0f4..dc2d5a0 100644 > > --- a/drivers/gpu/drm/i915/i915_drv.h > > +++ b/drivers/gpu/drm/i915/i915_drv.h > > @@ -2669,6 +2669,7 @@ struct i915_params { > > bool verbose_state_checks; > > bool nuclear_pageflip; > > int edp_vswing; > > + bool enable_dp_flt; > > }; > > extern struct i915_params i915 __read_mostly; > > > > diff --git a/drivers/gpu/drm/i915/i915_params.c > > b/drivers/gpu/drm/i915/i915_params.c > > index 835d609..aea5d47 100644 > > --- a/drivers/gpu/drm/i915/i915_params.c > > +++ b/drivers/gpu/drm/i915/i915_params.c > > @@ -56,6 +56,7 @@ struct i915_params i915 __read_mostly = { > > .edp_vswing = 0, > > .enable_guc_submission = false, > > .guc_log_level = -1, > > + .enable_dp_flt = false, > > }; > > > > module_param_named(modeset, i915.modeset, int, 0400); @@ -202,3 > > +203,6 @@ MODULE_PARM_DESC(enable_guc_submission, "Enable GuC > > submission (default:false)") module_param_named(guc_log_level, > > i915.guc_log_level, int, 0400); MODULE_PARM_DESC(guc_log_level, > > "GuC firmware logging level (-1:disabled (default), 0-3:enabled)"); > > + > > +module_param_named_unsafe(enable_dp_flt, i915.enable_dp_flt, bool, > > +0400); MODULE_PARM_DESC(enable_dp_flt, "Enable DP fast link training > > +(default:false)"); > > diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c > > b/drivers/gpu/drm/i915/intel_dp_link_training.c > > index 8888793..f8b6d69 100644 > > --- a/drivers/gpu/drm/i915/intel_dp_link_training.c > > +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c > > @@ -85,8 +85,17 @@ static bool > > intel_dp_reset_link_train(struct intel_dp *intel_dp, > > uint8_t dp_train_pat) > > { > > - if (!intel_dp->train_set_valid) > > + if (i915.enable_dp_flt) { > > + DRM_DEBUG_KMS("DP flt enabled, train set valid: %s\n", > > + intel_dp->train_set_valid ? "true" : "false"); > > + > > + if (!intel_dp->train_set_valid) > > + memset(intel_dp->train_set, 0, sizeof(intel_dp- > >train_set)); > > + } else { > > + DRM_DEBUG_KMS("DP flt disabled\n"); > > memset(intel_dp->train_set, 0, sizeof(intel_dp->train_set)); > > + } > > + > > intel_dp_set_signal_levels(intel_dp); > > return intel_dp_set_link_train(intel_dp, dp_train_pat); } > > -- > Jani Nikula, Intel Open Source Technology Center _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
