On Tue, 22 Dec 2015, Lukas Wunner <lu...@wunner.de> wrote:
> 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).
Good points, but we don't generally write code, let alone bugfixes, on
top of code that hasn't been merged.
BR,
Jani.
>
> 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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--
Jani Nikula, Intel Open Source Technology Center
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