Re: [PATCH v2 05/13] drm/i915/dp: generate and cache sink rate array for all DP, not just eDP 1.4

[Jani Nikula <jani.nikula@intel.com>]

On Fri, 03 Feb 2017, Ville Syrjälä <ville.syrjala@linux.intel.com> wrote:
> On Fri, Feb 03, 2017 at 04:19:28PM +0200, Jani Nikula wrote:
>> There is some conflation related to sink rates, making this change more
>> complicated than it would otherwise have to be. There are three changes
>> here that are rather difficult to split up:
>> 
>> 1) Use the intel_dp->sink_rates array for all DP, not just eDP 1.4. We
>>    initialize it from DPCD on eDP 1.4 like before, but generate it based
>>    on DP_MAX_LINK_RATE on others. This reduces code complexity when we
>>    need to use the sink rates; they are all always in the sink_rates
>>    array.
>> 
>> 2) Update the sink rate array whenever we read DPCD, and use the
>>    information from there. This increases code readability when we need
>>    the sink rates.
>> 
>> 3) Disentangle fallback rate limiting from sink rates. In the code, the
>>    max rate is a dynamic property of the *link*, not of the *sink*. Do
>>    the limiting after intersecting the source and sink rates, which are
>>    static properties of the devices.
>> 
>> This paves the way for follow-up refactoring that I've refrained from
>> doing here to keep this change as simple as it possibly can.
>> 
>> v2: introduce use_rate_select and handle non-confirming eDP (Ville)
>> 
>> Cc: Manasi Navare <manasi.d.navare@intel.com>
>> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
>> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
>> ---
>>  drivers/gpu/drm/i915/intel_dp.c               | 79 ++++++++++++++++++---------
>>  drivers/gpu/drm/i915/intel_dp_link_training.c |  3 +-
>>  drivers/gpu/drm/i915/intel_drv.h              |  5 +-
>>  3 files changed, 59 insertions(+), 28 deletions(-)
>> 
>> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
>> index 2378f0651cbd..66efe8044ac9 100644
>> --- a/drivers/gpu/drm/i915/intel_dp.c
>> +++ b/drivers/gpu/drm/i915/intel_dp.c
>> @@ -133,6 +133,34 @@ static void vlv_steal_power_sequencer(struct drm_device *dev,
>>  				      enum pipe pipe);
>>  static void intel_dp_unset_edid(struct intel_dp *intel_dp);
>>  
>> +static int intel_dp_num_rates(u8 link_bw_code)
>> +{
>> +	switch (link_bw_code) {
>> +	default:
>> +		WARN(1, "invalid max DP link bw val %x, using 1.62Gbps\n",
>> +		     link_bw_code);
>> +	case DP_LINK_BW_1_62:
>> +		return 1;
>> +	case DP_LINK_BW_2_7:
>> +		return 2;
>> +	case DP_LINK_BW_5_4:
>> +		return 3;
>> +	}
>> +}
>> +
>> +/* update sink rates from dpcd */
>> +static void intel_dp_set_sink_rates(struct intel_dp *intel_dp)
>> +{
>> +	int i, num_rates;
>> +
>> +	num_rates = intel_dp_num_rates(intel_dp->dpcd[DP_MAX_LINK_RATE]);
>> +
>> +	for (i = 0; i < num_rates; i++)
>> +		intel_dp->sink_rates[i] = default_rates[i];
>> +
>> +	intel_dp->num_sink_rates = num_rates;
>> +}
>> +
>>  static int
>>  intel_dp_max_link_bw(struct intel_dp  *intel_dp)
>>  {
>> @@ -205,19 +233,6 @@ intel_dp_downstream_max_dotclock(struct intel_dp *intel_dp)
>>  	return max_dotclk;
>>  }
>>  
>> -static int
>> -intel_dp_sink_rates(struct intel_dp *intel_dp, const int **sink_rates)
>> -{
>> -	if (intel_dp->num_sink_rates) {
>> -		*sink_rates = intel_dp->sink_rates;
>> -		return intel_dp->num_sink_rates;
>> -	}
>> -
>> -	*sink_rates = default_rates;
>> -
>> -	return (intel_dp->max_sink_link_bw >> 3) + 1;
>> -}
>> -
>>  static void
>>  intel_dp_set_source_rates(struct intel_dp *intel_dp)
>>  {
>> @@ -286,15 +301,22 @@ static int intel_dp_rate_index(const int *rates, int len, int rate)
>>  static int intel_dp_common_rates(struct intel_dp *intel_dp,
>>  				 int *common_rates)
>>  {
>> -	const int *sink_rates;
>> -	int sink_len;
>> +	int max_rate = drm_dp_bw_code_to_link_rate(intel_dp->max_sink_link_bw);
>> +	int i, common_len;
>>  
>> -	sink_len = intel_dp_sink_rates(intel_dp, &sink_rates);
>> +	common_len = intersect_rates(intel_dp->source_rates,
>> +				     intel_dp->num_source_rates,
>> +				     intel_dp->sink_rates,
>> +				     intel_dp->num_sink_rates,
>> +				     common_rates);
>>  
>> -	return intersect_rates(intel_dp->source_rates,
>> -			       intel_dp->num_source_rates,
>> -			       sink_rates, sink_len,
>> -			       common_rates);
>> +	/* Limit results by potentially reduced max rate */
>> +	for (i = 0; i < common_len; i++) {
>> +		if (common_rates[common_len - i - 1] <= max_rate)
>> +			return common_len - i;
>> +	}
>> +
>> +	return 0;
>>  }
>>  
>>  static int intel_dp_link_rate_index(struct intel_dp *intel_dp,
>> @@ -1502,8 +1524,7 @@ static void snprintf_int_array(char *str, size_t len,
>>  
>>  static void intel_dp_print_rates(struct intel_dp *intel_dp)
>>  {
>> -	const int *sink_rates;
>> -	int sink_len, common_len;
>> +	int common_len;
>>  	int common_rates[DP_MAX_SUPPORTED_RATES];
>>  	char str[128]; /* FIXME: too big for stack? */
>>  
>> @@ -1514,8 +1535,8 @@ static void intel_dp_print_rates(struct intel_dp *intel_dp)
>>  			   intel_dp->source_rates, intel_dp->num_source_rates);
>>  	DRM_DEBUG_KMS("source rates: %s\n", str);
>>  
>> -	sink_len = intel_dp_sink_rates(intel_dp, &sink_rates);
>> -	snprintf_int_array(str, sizeof(str), sink_rates, sink_len);
>> +	snprintf_int_array(str, sizeof(str),
>> +			   intel_dp->sink_rates, intel_dp->num_sink_rates);
>>  	DRM_DEBUG_KMS("sink rates: %s\n", str);
>>  
>>  	common_len = intel_dp_common_rates(intel_dp, common_rates);
>> @@ -1581,7 +1602,8 @@ int intel_dp_rate_select(struct intel_dp *intel_dp, int rate)
>>  void intel_dp_compute_rate(struct intel_dp *intel_dp, int port_clock,
>>  			   uint8_t *link_bw, uint8_t *rate_select)
>>  {
>> -	if (intel_dp->num_sink_rates) {
>> +	/* eDP 1.4 rate select method. */
>> +	if (intel_dp->use_rate_select) {
>>  		*link_bw = 0;
>>  		*rate_select =
>>  			intel_dp_rate_select(intel_dp, port_clock);
>> @@ -3718,6 +3740,11 @@ intel_edp_init_dpcd(struct intel_dp *intel_dp)
>>  		intel_dp->num_sink_rates = i;
>>  	}
>>  
>> +	if (intel_dp->num_sink_rates)
>> +		intel_dp->use_rate_select = true;
>> +	else
>> +		intel_dp_set_sink_rates(intel_dp);
>> +
>>  	return true;
>>  }
>>  
>> @@ -3728,6 +3755,8 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp)
>>  	if (!intel_dp_read_dpcd(intel_dp))
>>  		return false;
>>  
>> +	intel_dp_set_sink_rates(intel_dp);
>> +
>
> Isn't that going to clobber whatever intel_edp_init_dpcd() set up?

I think you're right, I missed the intel_dp_hpd_pulse ->
intel_dp_short_pulse -> intel_dp_get_dpcd path. Our eDP paths have been
separated from the DP paths quite a bit lately, but not completely.

I guess I'll need to make intel_dp_set_sink_rates() include all the eDP
stuff from intel_edp_init_dpcd(), to DTRT regardless of when it's
called.


BR,
Jani.



>
>>  	if (drm_dp_dpcd_read(&intel_dp->aux, DP_SINK_COUNT,
>>  			     &intel_dp->sink_count, 1) < 0)
>>  		return false;
>> diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c
>> index 0048b520baf7..694ad0ffb523 100644
>> --- a/drivers/gpu/drm/i915/intel_dp_link_training.c
>> +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
>> @@ -146,7 +146,8 @@ intel_dp_link_training_clock_recovery(struct intel_dp *intel_dp)
>>  		link_config[1] |= DP_LANE_COUNT_ENHANCED_FRAME_EN;
>>  	drm_dp_dpcd_write(&intel_dp->aux, DP_LINK_BW_SET, link_config, 2);
>>  
>> -	if (intel_dp->num_sink_rates)
>> +	/* eDP 1.4 rate select method. */
>> +	if (!link_bw)
>>  		drm_dp_dpcd_write(&intel_dp->aux, DP_LINK_RATE_SET,
>>  				  &rate_select, 1);
>>  
>> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
>> index f132d4aea1ad..3a6f092a2ec3 100644
>> --- a/drivers/gpu/drm/i915/intel_drv.h
>> +++ b/drivers/gpu/drm/i915/intel_drv.h
>> @@ -933,9 +933,10 @@ struct intel_dp {
>>  	/* source rates */
>>  	int num_source_rates;
>>  	const int *source_rates;
>> -	/* sink rates as reported by DP_SUPPORTED_LINK_RATES */
>> -	uint8_t num_sink_rates;
>> +	/* sink rates as reported by DP_MAX_LINK_RATE/DP_SUPPORTED_LINK_RATES */
>> +	int num_sink_rates;
>>  	int sink_rates[DP_MAX_SUPPORTED_RATES];
>> +	bool use_rate_select;
>>  	/* Max lane count for the sink as per DPCD registers */
>>  	uint8_t max_sink_lane_count;
>>  	/* Max link BW for the sink as per DPCD registers */
>> -- 
>> 2.1.4

-- 
Jani Nikula, Intel Open Source Technology Center
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