* [PATCH v2] drm/i915/dp: Use max params for panels < eDP 1.4
@ 2021-08-18 17:14 Kai-Heng Feng
2021-08-19 16:11 ` Ville Syrjälä
0 siblings, 1 reply; 2+ messages in thread
From: Kai-Heng Feng @ 2021-08-18 17:14 UTC (permalink / raw)
To: jani.nikula, joonas.lahtinen, rodrigo.vivi
Cc: Kai-Heng Feng, Ville Syrjälä,
David Airlie, Daniel Vetter, Imre Deak, Uma Shankar,
Manasi Navare, Ankit Nautiyal, José Roberto de Souza,
Sean Paul, intel-gfx, dri-devel, linux-kernel
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
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH v2] drm/i915/dp: Use max params for panels < eDP 1.4
2021-08-18 17:14 [PATCH v2] drm/i915/dp: Use max params for panels < eDP 1.4 Kai-Heng Feng
@ 2021-08-19 16:11 ` Ville Syrjälä
0 siblings, 0 replies; 2+ messages in thread
From: Ville Syrjälä @ 2021-08-19 16:11 UTC (permalink / raw)
To: Kai-Heng Feng
Cc: jani.nikula, joonas.lahtinen, rodrigo.vivi, David Airlie,
Daniel Vetter, Imre Deak, Uma Shankar, Manasi Navare,
Ankit Nautiyal, José Roberto de Souza, Sean Paul, intel-gfx,
dri-devel, linux-kernel
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
^ permalink raw reply [flat|nested] 2+ messages in thread
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