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 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"

> 
>      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
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