On Thu, 2016-08-11 at 15:23 -0700, Manasi Navare wrote:
> Intel_dp_link_is_valid() function reads the Link status registers
> and returns a boolean to indicate link is valid or not.
> If the link has lost lock and is not valid any more, link
> training is performed outside the function else previously trained link
> is retained.
> This gives us flexibility of checking whether link is valid and training
> it independently.
>
> v2:
> * Changed the function name from intel_dp_check_link_status()
> to intel_dp_link_is_valid() (Lukas Wunner)
> * Checks for CRTC and active CRTC are moved outside the
> intel_dp_link_is_valid() function (Rodrigo Vivi)
>
> Signed-off-by: Manasi Navare <manasi.d.navare@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/intel_dp.c | 56 +++++++++++++++++++++++++++--------------
> 1 file changed, 37 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 364db90..891147d 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -3881,36 +3881,33 @@ go_again:
> return -EINVAL;
> }
>
> -static void
> -intel_dp_check_link_status(struct intel_dp *intel_dp)
> +static bool
> +intel_dp_link_is_valid(struct intel_dp *intel_dp)
> {
> - struct intel_encoder *intel_encoder = &dp_to_dig_port(intel_dp)->base;
> struct drm_device *dev = intel_dp_to_dev(intel_dp);
> u8 link_status[DP_LINK_STATUS_SIZE];
>
> 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;
> + /* 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_DEBUG_KMS("Channel EQ or CR not ok, need to retrain\n");
drm_dp_channel_eq_ok() does not check for CR. Should we just say
"Channel EQ not ok" to preempt ambiguity while debugging ?
> + return false;
> + }
>
> - if (!to_intel_crtc(intel_encoder->base.crtc)->active)
> - return;
> + DRM_DEBUG_KMS("Link is good, no need to retrain\n");
The caller does not expect us to link train anymore, I don't think we
have to explicitly state "no need to retrain". Also, do we need debug
messages if the link is good?
> + 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:
> @@ -3928,6 +3925,8 @@ static bool
> intel_dp_short_pulse(struct intel_dp *intel_dp)
> {
> struct drm_device *dev = intel_dp_to_dev(intel_dp);
> + struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
> + struct intel_encoder *intel_encoder = &intel_dig_port->base;
> u8 sink_irq_vector = 0;
> u8 old_sink_count = intel_dp->sink_count;
> bool ret;
> @@ -3968,8 +3967,18 @@ intel_dp_short_pulse(struct intel_dp *intel_dp)
> DRM_DEBUG_DRIVER("CP or sink specific irq unhandled\n");
> }
>
> + /* Do not train the link if there is no crtc */
> + if (!intel_encoder->base.crtc)
> + return true;
> + if (!to_intel_crtc(intel_encoder->base.crtc)->active)
> + return true;
> +
I might be completely off base here. Shouldn't we keep the link valid
irrespective of whether there is an active crtc? I thought that is what
the refactoring is supposed to enable. Does intel_dp_short_pulse() get
called when there is a link loss during upfront link training? And in
that case, shouldn't we retrain even without a crtc?
Besides that, how about using just one return?
struct drm_crtc *crtc = intel_encoder->base.crtc;
if (crtc == NULL || !to_intel_crtc(crtc)->active)
return true;
> drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
> - intel_dp_check_link_status(intel_dp);
> + if (!intel_dp_link_is_valid(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;
> @@ -4298,8 +4307,17 @@ intel_dp_long_pulse(struct intel_connector *intel_connector)
> * check links status, there has been known issues of
> * link loss triggerring long pulse!!!!
> */
> + /* Do not train the link if there is no crtc */
> + if (!intel_encoder->base.crtc)
> + goto out;
> + if (!to_intel_crtc(intel_encoder->base.crtc)->active)
> + goto out;
> +
> drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
> - intel_dp_check_link_status(intel_dp);
> + if (!intel_dp_link_is_valid(intel_dp)) {
> + intel_dp_start_link_train(intel_dp);
> + intel_dp_stop_link_train(intel_dp);
> + }
> drm_modeset_unlock(&dev->mode_config.connection_mutex);
> goto out;
> }
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