Hi Mika,
On Mon, Dec 21, 2015 at 01:39:15PM +0200, Mika Kahola wrote:
> Check if no AUX transactions are required on DP link training.
> If this bit is set, we can reuse the known good drive current
> and pre-emphasis level from the last "full" link training.
>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=91393
> Signed-off-by: Mika Kahola <mika.kah...@intel.com>
> ---
> drivers/gpu/drm/i915/intel_dp.c | 2 +-
> drivers/gpu/drm/i915/intel_dp_link_training.c | 19 +++++++++++++++++++
> drivers/gpu/drm/i915/intel_drv.h | 1 +
> 3 files changed, 21 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 6b36d82..3137187 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -3852,7 +3852,7 @@ intel_dp_link_down(struct intel_dp *intel_dp)
> intel_dp->DP = DP;
> }
>
> -static bool
> +bool
> intel_dp_get_dpcd(struct intel_dp *intel_dp)
> {
> struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp);
> diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c
> b/drivers/gpu/drm/i915/intel_dp_link_training.c
> index 59d59be..5fb3f97 100644
> --- a/drivers/gpu/drm/i915/intel_dp_link_training.c
> +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
> @@ -85,6 +85,25 @@ static bool
> intel_dp_reset_link_train(struct intel_dp *intel_dp,
> uint8_t dp_train_pat)
> {
> + bool has_dpcd;
> + bool no_aux_handshake = false;
> +
> + has_dpcd = intel_dp_get_dpcd(intel_dp);
> +
> + /*
> + * Source device can try to use drive current and pre-emphasis
> + * parameters computed by the last "full" link training if the
> + * DP_NO_AUX_HANDSHAKE_LINK_TRAINING bit is set to 1.
> + */
> + if (has_dpcd) {
> + if (intel_dp->dpcd[DP_DPCD_REV] >= 0x11) {
> + no_aux_handshake = (intel_dp->dpcd[DP_MAX_DOWNSPREAD] &
> + DP_NO_AUX_HANDSHAKE_LINK_TRAINING);
> + }
> + }
> +
> + intel_dp->train_set_valid &= no_aux_handshake;
> +
If Thierry Reding's patches get merged (posted to dri-devel@ on Dec 14
with <1450097764-30063-1-git-send-email-thierry.red...@gmail.com>),
you could just use
if (has_dpcd && drm_dp_fast_training_cap(intel_dp->dpcd))
intel_dp->train_set_valid &= true;
Also, if the patches get merged, the no_aux_handshake attribute in dev_priv
can be dropped (set in intel_edp_init_connector() but never read).
Best regards,
Lukas
> DRM_DEBUG_KMS("link training optimization: %s\n",
> intel_dp->train_set_valid ? "true" : "false");
>
> diff --git a/drivers/gpu/drm/i915/intel_drv.h
> b/drivers/gpu/drm/i915/intel_drv.h
> index d523ebb..c36a70c 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -1239,6 +1239,7 @@ int intel_dp_sink_crc(struct intel_dp *intel_dp, u8
> *crc);
> bool intel_dp_compute_config(struct intel_encoder *encoder,
> struct intel_crtc_state *pipe_config);
> bool intel_dp_is_edp(struct drm_device *dev, enum port port);
> +bool intel_dp_get_dpcd(struct intel_dp *intel_dp);
> enum irqreturn intel_dp_hpd_pulse(struct intel_digital_port *intel_dig_port,
> bool long_hpd);
> void intel_edp_backlight_on(struct intel_dp *intel_dp);
> --
> 1.9.1
>
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> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx
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