Re: [PATCH] drm/i915: intel_dp_check_link_status should only return status of link

Rodrigo Vivi
2016-07-02T00:35:27Z

On Fri, Jul 1, 2016 at 3:47 PM, Manasi Navare <manasi.d.navare@intel.com> wrote:
> Intel_dp_check_link_status() function reads the Link status registers
> and returns a boolean to indicate link is good or bad.
> If the link is bad, it is retrained outside the function based
> on the return value.
>
> Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> ---
> drivers/gpu/drm/i915/intel_dp.c | 41 ++++++++++++++++++++++++-----------------
> 1 file changed, 24 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 6d586b7..c795c9e 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -3863,7 +3863,7 @@ go_again:
> return -EINVAL;
> }
>
> -static void
> +static bool
> intel_dp_check_link_status(struct intel_dp *intel_dp)
> {
> struct intel_encoder *intel_encoder = &dp_to_dig_port(intel_dp)->base;
> @@ -3873,26 +3873,25 @@ intel_dp_check_link_status(struct intel_dp *intel_dp)
> WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex));
>
> if (!intel_dp_get_link_status(intel_dp, link_status)) {
> - DRM_ERROR("Failed to get link status\n");
> - return;
> + DRM_DEBUG_KMS("Failed to get link status\n");
> + return false;
> }
>
> - if (!intel_encoder->base.crtc)
> - return;

where did this check go? why don't we need this anymore?

> + /* Check if the link is valid by reading the bits of Link status
> + * registers
> + */
> + if (!drm_dp_channel_eq_ok(link_status, intel_dp->lane_count) ||
> + !drm_dp_clock_recovery_ok(link_status, intel_dp->lane_count)) {
> + DRM_DEBUG_KMS("Channel EQ or CR not ok, need to retrain\n");
> + return false;
> + }
>
> - if (!to_intel_crtc(intel_encoder->base.crtc)->active)
> - return;

what happens if it is not active now? are we going to attemtp the
retraing in this case?
in other words: we really don't need this check anymore as the one above?

Thanks,
Rodrigo.

> + DRM_DEBUG_KMS("Link is good, no need to retrain\n");
> + return true;
>
> - /* if link training is requested we should perform it always */
> - if ((intel_dp->compliance_test_type == DP_TEST_LINK_TRAINING) ||
> - (!drm_dp_channel_eq_ok(link_status, intel_dp->lane_count))) {
> - DRM_DEBUG_KMS("%s: channel EQ not ok, retraining\n",
> - intel_encoder->base.name);
> - intel_dp_start_link_train(intel_dp);
> - intel_dp_stop_link_train(intel_dp);
> - }
> }
>
> +
> /*
> * According to DP spec
> * 5.1.2:
> @@ -3950,7 +3949,11 @@ intel_dp_short_pulse(struct intel_dp *intel_dp)
> }
>
> drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
> - intel_dp_check_link_status(intel_dp);
> + if (!intel_dp_check_link_status(intel_dp) ||
> + intel_dp->compliance_test_type == DP_TEST_LINK_TRAINING) {
> + intel_dp_start_link_train(intel_dp);
> + intel_dp_stop_link_train(intel_dp);
> + }
> drm_modeset_unlock(&dev->mode_config.connection_mutex);
>
> return true;
> @@ -4271,7 +4274,11 @@ intel_dp_long_pulse(struct intel_connector *intel_connector)
> * link loss triggerring long pulse!!!!
> */
> drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
> - intel_dp_check_link_status(intel_dp);
> + if (!intel_dp_check_link_status(intel_dp) ||
> + intel_dp->compliance_test_type == DP_TEST_LINK_TRAINING) {
> + intel_dp_start_link_train(intel_dp);
> + intel_dp_stop_link_train(intel_dp);
> + }
> drm_modeset_unlock(&dev->mode_config.connection_mutex);
> goto out;
> }
> --
> 1.9.1
>
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--
Rodrigo Vivi
Blog: http://blog.vivi.eng.br