[Intel-gfx] [PATCH v2] drm/i915/dp: Use max params for panels < eDP 1.4

[Intel-gfx] [PATCH v2] drm/i915/dp: Use max params for panels < eDP 1.4

[Kai-Heng Feng]

Users reported that after commit 2bbd6dba84d4 ("drm/i915: Try to use
fast+narrow link on eDP again and fall back to the old max strategy on
failure"), the screen starts to have wobbly effect.

Commit a5c936add6a2 ("drm/i915/dp: Use slow and wide link training for
everything") doesn't help either, that means the affected eDP 1.2 panels
only work with max params.

So use max params for panels < eDP 1.4 as Windows does to solve the
issue.

v2:
 - Check eDP 1.4 instead of DPCD 1.1 to apply max params

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/3714
Fixes: 2bbd6dba84d4 ("drm/i915: Try to use fast+narrow link on eDP again and fall back to the old max strategy on failure")
Fixes: a5c936add6a2 ("drm/i915/dp: Use slow and wide link training for everything")
Suggested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
---
 drivers/gpu/drm/i915/display/intel_dp.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 75d4ebc669411..f87fad78f1a9f 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -1330,14 +1330,16 @@ intel_dp_compute_link_config(struct intel_encoder *encoder,
 	limits.min_bpp = intel_dp_min_bpp(pipe_config->output_format);
 	limits.max_bpp = intel_dp_max_bpp(intel_dp, pipe_config);
 
-	if (intel_dp->use_max_params) {
+	if (intel_dp->use_max_params ||
+	    intel_dp->edp_dpcd[0] < DP_EDP_14) {
 		/*
 		 * Use the maximum clock and number of lanes the eDP panel
 		 * advertizes being capable of in case the initial fast
-		 * optimal params failed us. The panels are generally
-		 * designed to support only a single clock and lane
-		 * configuration, and typically on older panels these
-		 * values correspond to the native resolution of the panel.
+		 * optimal params failed us or the EDP rev is earlier than 1.4.
+		 * The panels are generally designed to support only a single
+		 * clock and lane configuration, and typically on older panels
+		 * these values correspond to the native resolution of the
+		 * panel.
 		 */
 		limits.min_lane_count = limits.max_lane_count;
 		limits.min_clock = limits.max_clock;
-- 
2.32.0

[Intel-gfx] ✗ Fi.CI.CHECKPATCH: warning for drm/i915/dp: Use max params for panels < eDP 1.4

[Patchwork]

== Series Details ==

Series: drm/i915/dp: Use max params for panels < eDP 1.4
URL   : https://patchwork.freedesktop.org/series/93794/
State : warning

== Summary ==

$ dim checkpatch origin/drm-tip
33297386de4a drm/i915/dp: Use max params for panels < eDP 1.4
-:9: ERROR:GIT_COMMIT_ID: Please use git commit description style 'commit <12+ chars of sha1> ("<title line>")' - ie: 'commit 2bbd6dba84d4 ("drm/i915: Try to use fast+narrow link on eDP again and fall back to the old max strategy on failure")'
#9: 
Users reported that after commit 2bbd6dba84d4 ("drm/i915: Try to use

total: 1 errors, 0 warnings, 0 checks, 21 lines checked

[Intel-gfx] ✗ Fi.CI.BAT: failure for drm/i915/dp: Use max params for panels < eDP 1.4

[Patchwork]

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== Series Details ==

Series: drm/i915/dp: Use max params for panels < eDP 1.4
URL   : https://patchwork.freedesktop.org/series/93794/
State : failure

== Summary ==

CI Bug Log - changes from CI_DRM_10497 -> Patchwork_20849
====================================================

Summary
-------

  **FAILURE**

  Serious unknown changes coming with Patchwork_20849 absolutely need to be
  verified manually.
  
  If you think the reported changes have nothing to do with the changes
  introduced in Patchwork_20849, please notify your bug team to allow them
  to document this new failure mode, which will reduce false positives in CI.

  External URL: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_20849/index.html

Possible new issues
-------------------

  Here are the unknown changes that may have been introduced in Patchwork_20849:

### IGT changes ###

#### Possible regressions ####

  * igt@debugfs_test@read_all_entries:
    - fi-tgl-1115g4:      NOTRUN -> [DMESG-WARN][1]
   [1]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_20849/fi-tgl-1115g4/igt@debugfs_test@read_all_entries.html

  * igt@gem_ctx_create@basic-files:
    - fi-tgl-1115g4:      NOTRUN -> [INCOMPLETE][2]
   [2]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_20849/fi-tgl-1115g4/igt@gem_ctx_create@basic-files.html

  
Known issues
------------

  Here are the changes found in Patchwork_20849 that come from known issues:

### IGT changes ###

#### Issues hit ####

  * igt@amdgpu/amd_basic@cs-gfx:
    - fi-rkl-guc:         NOTRUN -> [SKIP][3] ([fdo#109315]) +17 similar issues
   [3]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_20849/fi-rkl-guc/igt@amdgpu/amd_basic@cs-gfx.html
    - fi-kbl-soraka:      NOTRUN -> [SKIP][4] ([fdo#109271]) +13 similar issues
   [4]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_20849/fi-kbl-soraka/igt@amdgpu/amd_basic@cs-gfx.html

  * igt@runner@aborted:
    - fi-tgl-1115g4:      NOTRUN -> [FAIL][5] ([i915#2722])
   [5]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_20849/fi-tgl-1115g4/igt@runner@aborted.html

  
#### Possible fixes ####

  * igt@core_hotunplug@unbind-rebind:
    - fi-rkl-guc:         [DMESG-WARN][6] ([i915#3925]) -> [PASS][7]
   [6]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_10497/fi-rkl-guc/igt@core_hotunplug@unbind-rebind.html
   [7]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_20849/fi-rkl-guc/igt@core_hotunplug@unbind-rebind.html

  
  [fdo#109271]: https://bugs.freedesktop.org/show_bug.cgi?id=109271
  [fdo#109315]: https://bugs.freedesktop.org/show_bug.cgi?id=109315
  [i915#2722]: https://gitlab.freedesktop.org/drm/intel/issues/2722
  [i915#3925]: https://gitlab.freedesktop.org/drm/intel/issues/3925


Participating hosts (34 -> 33)
------------------------------

  Additional (1): fi-tgl-1115g4 
  Missing    (2): fi-bsw-cyan fi-kbl-guc 


Build changes
-------------

  * Linux: CI_DRM_10497 -> Patchwork_20849

  CI-20190529: 20190529
  CI_DRM_10497: c50a8ea72915f1e3972d011690a423bafbee7a58 @ git://anongit.freedesktop.org/gfx-ci/linux
  IGT_6178: 146260200f9a6d4536e48a195e2ab49a07d4f0c1 @ https://gitlab.freedesktop.org/drm/igt-gpu-tools.git
  Patchwork_20849: 33297386de4af8318a8c52f3684f130eb55823eb @ git://anongit.freedesktop.org/gfx-ci/linux


== Linux commits ==

33297386de4a drm/i915/dp: Use max params for panels < eDP 1.4

== Logs ==

For more details see: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_20849/index.html

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Re: [Intel-gfx] [PATCH v2] drm/i915/dp: Use max params for panels < eDP 1.4

[Ville Syrjälä]

On Thu, Aug 19, 2021 at 01:14:55AM +0800, Kai-Heng Feng wrote:
> Users reported that after commit 2bbd6dba84d4 ("drm/i915: Try to use
> fast+narrow link on eDP again and fall back to the old max strategy on
> failure"), the screen starts to have wobbly effect.
> 
> Commit a5c936add6a2 ("drm/i915/dp: Use slow and wide link training for
> everything") doesn't help either, that means the affected eDP 1.2 panels
> only work with max params.
> 
> So use max params for panels < eDP 1.4 as Windows does to solve the
> issue.
> 
> v2:
>  - Check eDP 1.4 instead of DPCD 1.1 to apply max params
> 
> Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/3714
> Fixes: 2bbd6dba84d4 ("drm/i915: Try to use fast+narrow link on eDP again and fall back to the old max strategy on failure")
> Fixes: a5c936add6a2 ("drm/i915/dp: Use slow and wide link training for everything")
> Suggested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
> ---
>  drivers/gpu/drm/i915/display/intel_dp.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index 75d4ebc669411..f87fad78f1a9f 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -1330,14 +1330,16 @@ intel_dp_compute_link_config(struct intel_encoder *encoder,
>  	limits.min_bpp = intel_dp_min_bpp(pipe_config->output_format);
>  	limits.max_bpp = intel_dp_max_bpp(intel_dp, pipe_config);
>  
> -	if (intel_dp->use_max_params) {
> +	if (intel_dp->use_max_params ||
> +	    intel_dp->edp_dpcd[0] < DP_EDP_14) {

I think we're going to need a is_edp check here or else we'll always
take this path on extenral DP when edp_dpcd[] is zeroed.

Hmm. Maybe just stick
intel_dp->use_max_params = intel_dp->edp_dpcd[0] < DP_EDP_14;
into intel_edp_init_dpcd()?

>  		/*
>  		 * Use the maximum clock and number of lanes the eDP panel
>  		 * advertizes being capable of in case the initial fast
> -		 * optimal params failed us. The panels are generally
> -		 * designed to support only a single clock and lane
> -		 * configuration, and typically on older panels these
> -		 * values correspond to the native resolution of the panel.
> +		 * optimal params failed us or the EDP rev is earlier than 1.4.
> +		 * The panels are generally designed to support only a single
> +		 * clock and lane configuration, and typically on older panels
> +		 * these values correspond to the native resolution of the
> +		 * panel.
>  		 */
>  		limits.min_lane_count = limits.max_lane_count;
>  		limits.min_clock = limits.max_clock;
> -- 
> 2.32.0

-- 
Ville Syrjälä
Intel