On Thu, May 17, 2018 at 12:28 AM, Jani Nikula
<jani.nikula@xxxxxxxxxxxxxxx> wrote:
> On Wed, 16 May 2018, Manasi Navare <manasi.d.navare@xxxxxxxxx> wrote:
>> This patch fixes the original commit c0cfb10d9e1de49 ("drm/i915/edp:
>> Do not do link training fallback or prune modes on EDP") that causes
>> a blank screen in case of certain eDP panels (Eg: seen on Dell XPS13 9350)
>> where first link training fails and a retraining is required by falling
>> back to lower link rate/lane count.
>> In case of some panels they advertise higher link rate/lane count
>> than whats required for supporting the panel's native mode.
>> But we always link train at highest link rate/lane count for eDP
>> and if that fails we can still fallback to lower link rate/lane count
>> as long as the fallback link BW still fits the native mode to avoid
>> pruning the panel's native mode yet retraining at fallback values
>> to recover from a blank screen.
>
> What eDP revision is the faulty panel? Does [1] help for that? Then we'd
> not need this.
# dd if=/dev/drm_dp_aux0 bs=1 | hexdump -C
...
00000700 02
So, should be eDP rev 1.3
>
> I think this also ties in with the alternate/downclock mode. It fails
> now and should be reverted [2]. However, if we know the panel has a
> valid mode with lower refresh rate, we might have a mode that actually
> fits a link with reduced bandwidth.
>
> IMO we need [1], [2], and patches to disconnect downclock mode from drrs
> support (so we/user can choose the downclock mode independent of drrs),
> and finally eDP link fallback selection based on if there's a downclock
> mode and if it fits a link with reduced link rate or lane count.
>
> BR,
> Jani.
>
>
> [1] http://patchwork.freedesktop.org/patch/msgid/20180509071321.28563-1-jani.nikula@xxxxxxxxx
> [2] http://patchwork.freedesktop.org/patch/msgid/20180516080110.22770-1-jani.nikula@xxxxxxxxx
Tested both patches and still the same problem.
Lucas De Marchi
>
>
>
>>
>> Cc: Clinton Taylor <clinton.a.taylor@xxxxxxxxx>
>> Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>
>> Cc: Ville Syrjala <ville.syrjala@xxxxxxxxxxxxxxx>
>> Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
>> Cc: Lucas De Marchi <lucas.demarchi@xxxxxxxxx>
>> Signed-off-by: Manasi Navare <manasi.d.navare@xxxxxxxxx>
>> ---
>> drivers/gpu/drm/i915/intel_dp.c | 25 +++++++++++++++++++++++++
>> drivers/gpu/drm/i915/intel_dp_link_training.c | 26 +++++++++-----------------
>> 2 files changed, 34 insertions(+), 17 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
>> index 2cc58596..7f7202a 100644
>> --- a/drivers/gpu/drm/i915/intel_dp.c
>> +++ b/drivers/gpu/drm/i915/intel_dp.c
>> @@ -387,6 +387,21 @@ static bool intel_dp_link_params_valid(struct intel_dp *intel_dp, int link_rate,
>> return true;
>> }
>>
>> +static bool intel_dp_can_link_train_fallback_for_edp(struct intel_dp *intel_dp,
>> + int link_rate,
>> + uint8_t lane_count)
>> +{
>> + struct drm_display_mode *fixed_mode = intel_dp->attached_connector->panel.fixed_mode;
>> + int mode_rate, max_rate;
>> +
>> + mode_rate = intel_dp_link_required(fixed_mode->clock, 18);
>> + max_rate = intel_dp_max_data_rate(link_rate, lane_count);
>> + if (mode_rate > max_rate)
>> + return false;
>> +
>> + return true;
>> +}
>> +
>> int intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
>> int link_rate, uint8_t lane_count)
>> {
>> @@ -396,9 +411,19 @@ int intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
>> intel_dp->num_common_rates,
>> link_rate);
>> if (index > 0) {
>> + if (intel_dp_is_edp(intel_dp) &&
>> + !intel_dp_can_link_train_fallback_for_edp(intel_dp,
>> + intel_dp->common_rates[index-1],
>> + lane_count))
>> + return -1;
>> intel_dp->max_link_rate = intel_dp->common_rates[index - 1];
>> intel_dp->max_link_lane_count = lane_count;
>> } else if (lane_count > 1) {
>> + if (intel_dp_is_edp(intel_dp) &&
>> + !intel_dp_can_link_train_fallback_for_edp(intel_dp,
>> + intel_dp_max_common_rate(intel_dp),
>> + lane_count >> 1))
>> + return -1;
>> intel_dp->max_link_rate = intel_dp_max_common_rate(intel_dp);
>> intel_dp->max_link_lane_count = lane_count >> 1;
>> } else {
>> diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c
>> index 3fcaa98..6673975 100644
>> --- a/drivers/gpu/drm/i915/intel_dp_link_training.c
>> +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
>> @@ -335,22 +335,14 @@ intel_dp_start_link_train(struct intel_dp *intel_dp)
>> return;
>>
>> failure_handling:
>> - /* Dont fallback and prune modes if its eDP */
>> - if (!intel_dp_is_edp(intel_dp)) {
>> - DRM_DEBUG_KMS("[CONNECTOR:%d:%s] Link Training failed at link rate = %d, lane count = %d",
>> - intel_connector->base.base.id,
>> - intel_connector->base.name,
>> - intel_dp->link_rate, intel_dp->lane_count);
>> - if (!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 */
>> - schedule_work(&intel_connector->modeset_retry_work);
>> - } else {
>> - DRM_ERROR("[CONNECTOR:%d:%s] Link Training failed at link rate = %d, lane count = %d",
>> - intel_connector->base.base.id,
>> - intel_connector->base.name,
>> - intel_dp->link_rate, intel_dp->lane_count);
>> - }
>> + DRM_DEBUG_KMS("[CONNECTOR:%d:%s] Link Training failed at link rate = %d, lane count = %d",
>> + intel_connector->base.base.id,
>> + intel_connector->base.name,
>> + intel_dp->link_rate, intel_dp->lane_count);
>> + if (!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 */
>> + schedule_work(&intel_connector->modeset_retry_work);
>> return;
>> }
>
> --
> Jani Nikula, Intel Open Source Technology Center
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> Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
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--
Lucas De Marchi
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