[PATCH v7 3/4] drm/i915: Find fallback link rate/lane count

[Jani Nikula]

On Fri, 09 Dec 2016, Jani Nikula <jani.nikula at linux.intel.com> wrote:
> On Fri, 09 Dec 2016, Manasi Navare <manasi.d.navare at intel.com> wrote:
>> If link training fails, then we need to fallback to lower
>> link rate first and if link training fails at RBR, then
>> fallback to lower lane count.
>> This function finds the next lower link rate/lane count
>> value after link training failure and limits the max
>> link_rate and lane_count values to these fallback values.
>>
>> v7:
>> * Remove unnecessary intializations and remove redundant
>> call to intel_dp_common_rates (Jani Nikula)
>> v6:
>> * Cap the max link rate and lane count to the max
>> values obtained during fallback link training (Daniel Vetter)
>> v5:
>> * Start the fallback at the lane count value passed not
>> the max lane count (Jani Nikula)
>> v4:
>> * Remove the redundant variable link_train_failed
>> v3:
>> * Remove fallback_link_rate_index variable, just obtain
>> that using the helper intel_dp_link_rate_index (Jani Nikula)
>> v2:
>> Squash the patch that returns the link rate index (Jani Nikula)
>>
>> Acked-by: Tony Cheng <tony.cheng at amd.com>
>> Acked-by: Harry Wentland <harry.wentland at amd.com>
>> Cc: Ville Syrjala <ville.syrjala at linux.intel.com>
>> Cc: Jani Nikula <jani.nikula at linux.intel.com>
>> Cc: Daniel Vetter <daniel.vetter at intel.com>
>> Signed-off-by: Manasi Navare <manasi.d.navare at intel.com>
>
> Reviewed-by: Jani Nikula <jani.nikula at intel.com>

And pushed this one to dinq, thanks for the patch.

BR,
Jani.

>
>
>> ---
>>  drivers/gpu/drm/i915/intel_dp.c  | 38 ++++++++++++++++++++++++++++++++++++++
>>  drivers/gpu/drm/i915/intel_drv.h |  2 ++
>>  2 files changed, 40 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
>> index 434dc7d..1b5e0d0 100644
>> --- a/drivers/gpu/drm/i915/intel_dp.c
>> +++ b/drivers/gpu/drm/i915/intel_dp.c
>> @@ -278,6 +278,44 @@ static int intel_dp_common_rates(struct intel_dp *intel_dp,
>>  			       common_rates);
>>  }
>>  
>> +static int intel_dp_link_rate_index(struct intel_dp *intel_dp,
>> +				    int *common_rates, int link_rate)
>> +{
>> +	int common_len;
>> +	int index;
>> +
>> +	common_len = intel_dp_common_rates(intel_dp, common_rates);
>> +	for (index = 0; index < common_len; index++) {
>> +		if (link_rate == common_rates[common_len - index - 1])
>> +			return common_len - index - 1;
>> +	}
>> +
>> +	return -1;
>> +}
>> +
>> +int intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
>> +					    int link_rate, uint8_t lane_count)
>> +{
>> +	int common_rates[DP_MAX_SUPPORTED_RATES];
>> +	int link_rate_index;
>> +
>> +	link_rate_index = intel_dp_link_rate_index(intel_dp,
>> +						   common_rates,
>> +						   link_rate);
>> +	if (link_rate_index > 0) {
>> +		intel_dp->max_sink_link_bw = drm_dp_link_rate_to_bw_code(common_rates[link_rate_index - 1]);
>> +		intel_dp->max_sink_lane_count = lane_count;
>> +	} else if (lane_count > 1) {
>> +		intel_dp->max_sink_link_bw = intel_dp_max_link_bw(intel_dp);
>> +		intel_dp->max_sink_lane_count = lane_count >> 1;
>> +	} else {
>> +		DRM_ERROR("Link Training Unsuccessful\n");
>> +		return -1;
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>>  static enum drm_mode_status
>>  intel_dp_mode_valid(struct drm_connector *connector,
>>  		    struct drm_display_mode *mode)
>> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
>> index 377693e..0a20422 100644
>> --- a/drivers/gpu/drm/i915/intel_drv.h
>> +++ b/drivers/gpu/drm/i915/intel_drv.h
>> @@ -1400,6 +1400,8 @@ bool intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
>>  void intel_dp_set_link_params(struct intel_dp *intel_dp,
>>  			      int link_rate, uint8_t lane_count,
>>  			      bool link_mst);
>> +int intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
>> +					    int link_rate, uint8_t lane_count);
>>  void intel_dp_start_link_train(struct intel_dp *intel_dp);
>>  void intel_dp_stop_link_train(struct intel_dp *intel_dp);
>>  void intel_dp_sink_dpms(struct intel_dp *intel_dp, int mode);

-- 
Jani Nikula, Intel Open Source Technology Center