Re: [PATCH] drm/i915: Do not do link training fallback or prune modes for eDP

[Manasi Navare <manasi.d.navare@intel.com>]

On Thu, Aug 17, 2017 at 02:01:05PM -0700, Manasi Navare wrote:
> On Thu, Aug 17, 2017 at 01:11:00PM -0700, Pandiyan, Dhinakaran wrote:
> > On Thu, 2017-08-17 at 12:46 -0700, Manasi Navare wrote:
> > > On Thu, Aug 17, 2017 at 07:01:05AM +0000, Rodrigo Vivi wrote:
> > > >    On Wed, Aug 16, 2017 at 11:51 PM Manasi Navare
> > > >    <[1]manasi.d.navare@intel.com> wrote:
> > > > 
> > > >      In case of eDP because the panel has a fixed mode we cannot
> > > >      link train fallback and prune modes since this results in
> > > >      no modes available for eDP connector.
> > > > 
> > > >    What about downclock modes?!
> > > 
> > > What are the downclock modes? We have seen an issue with pruning modes
> > > in case of eDP panel where we end up pruning the mode due to link train
> > > fallback and then we get an error saying "No modes available for the
> > > connector"
> > > 
> > 
> > fwiw I've got two laptops with eDP's having more than ten modes.
> >

Hmm, I have always dealt with laptops with eDPs with a fixed mode
and so are the systems in CI which are giving this "no mode
left on the connector error".

Manasi

> 
> Yes but link training is not supposed to fail for eDP since its a
> fixed connection and so after discussing with Daniel and Jani, this is
> the consensus that we shouldnt be falling back and retraining in case
> of eDP since most eDP panels are going to have 1 or 2 modes.
> 
> Manasi
>  
> > > > 
> > > >      Also since its a panel, link training should not fail dynamically
> > > >      based on cable conditions like in  case of DP.
> > > > 
> > > >    Is there any bug associated with this patch?
> > > 
> > > Yes this is the bug:
> > > https://bugs.freedesktop.org/show_bug.cgi?id=101518
> > > But the reason I didnt have this in the Fixes tab is because
> > > this patch will not fix the bug, it will just isolate to it being
> > > a bug with AUX Timeouts warning.
> > > 
> > > Regards
> > > Manasi
> > > 
> > > > 
> > > >      Cc: Jani Nikula <[2]jani.nikula@linux.intel.com>
> > > >      Cc: Jim Bride <[3]jim.bride@linux.intel.com>
> > > >      Cc: Ville Syrjälä <[4]ville.syrjala@linux.intel.com>
> > > >      Cc: Daniel Vetter <[5]daniel.vetter@intel.com>
> > > >      Signed-off-by: Manasi Navare <[6]manasi.d.navare@intel.com>
> > > >      ---
> > > >       drivers/gpu/drm/i915/intel_dp.c               | 2 +-
> > > >       drivers/gpu/drm/i915/intel_dp_link_training.c | 3 ++-
> > > >       drivers/gpu/drm/i915/intel_drv.h              | 1 +
> > > >       3 files changed, 4 insertions(+), 2 deletions(-)
> > > >      diff --git a/drivers/gpu/drm/i915/intel_dp.c
> > > >      b/drivers/gpu/drm/i915/intel_dp.c
> > > >      index 4fd4853..edac0c8 100644
> > > >      --- a/drivers/gpu/drm/i915/intel_dp.c
> > > >      +++ b/drivers/gpu/drm/i915/intel_dp.c
> > > >      @@ -109,7 +109,7 @@ static const int default_rates[] = { 162000,
> > > >      270000, 540000 };
> > > >        * If a CPU or PCH DP output is attached to an eDP panel, this
> > > >      function
> > > >        * will return true, and false otherwise.
> > > >        */
> > > >      -static bool is_edp(struct intel_dp *intel_dp)
> > > >      +bool is_edp(struct intel_dp *intel_dp)
> > > >       {
> > > >              struct intel_digital_port *intel_dig_port =
> > > >      dp_to_dig_port(intel_dp);
> > > >      diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c
> > > >      b/drivers/gpu/drm/i915/intel_dp_link_training.c
> > > >      index 05907fa..18ec61f 100644
> > > >      --- a/drivers/gpu/drm/i915/intel_dp_link_training.c
> > > >      +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
> > > >      @@ -332,7 +332,8 @@ intel_dp_start_link_train(struct intel_dp
> > > >      *intel_dp)
> > > >                            intel_connector->[7]base.base.id,
> > > >                            intel_connector->[8]base.name,
> > > >                            intel_dp->link_rate, intel_dp->lane_count);
> > > >      -       if (!intel_dp_get_link_train_fallback_values(intel_dp,
> > > >      +       /* Dont fallback and prune modes if its eDP */
> > > >      +       if (!is_edp(intel_dp) &&
> > > >      !intel_dp_get_link_train_fallback_values(intel_dp,
> > > > 
> > > >      intel_dp->link_rate,
> > > > 
> > > >      intel_dp->lane_count))
> > > >                      /* Schedule a Hotplug Uevent to userspace to start
> > > >      modeset */
> > > >      diff --git a/drivers/gpu/drm/i915/intel_drv.h
> > > >      b/drivers/gpu/drm/i915/intel_drv.h
> > > >      index fa47285..9800a15 100644
> > > >      --- a/drivers/gpu/drm/i915/intel_drv.h
> > > >      +++ b/drivers/gpu/drm/i915/intel_drv.h
> > > >      @@ -1548,6 +1548,7 @@ static inline unsigned int
> > > >      intel_dp_unused_lane_mask(int lane_count)
> > > >       }
> > > >       bool intel_dp_read_dpcd(struct intel_dp *intel_dp);
> > > >      +bool is_edp(struct intel_dp *intel_dp);
> > > >       int intel_dp_link_required(int pixel_clock, int bpp);
> > > >       int intel_dp_max_data_rate(int max_link_clock, int max_lanes);
> > > >       bool intel_digital_port_connected(struct drm_i915_private
> > > >      *dev_priv,
> > > >      --
> > > >      2.1.4
> > > >      _______________________________________________
> > > >      Intel-gfx mailing list
> > > >      [9]Intel-gfx@lists.freedesktop.org
> > > >      [10]https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> > > > 
> > > > References
> > > > 
> > > >    1. mailto:manasi.d.navare@intel.com
> > > >    2. mailto:jani.nikula@linux.intel.com
> > > >    3. mailto:jim.bride@linux.intel.com
> > > >    4. mailto:ville.syrjala@linux.intel.com
> > > >    5. mailto:daniel.vetter@intel.com
> > > >    6. mailto:manasi.d.navare@intel.com
> > > >    7. http://base.base.id/
> > > >    8. http://base.name/
> > > >    9. mailto:Intel-gfx@lists.freedesktop.org
> > > >   10. https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> > > _______________________________________________
> > > Intel-gfx mailing list
> > > Intel-gfx@lists.freedesktop.org
> > > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
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