Re: [PATCH v3 2/6] drm/i915: Remove the link rate and lane count loop in compute config

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

On Wed, 28 Sep 2016, Manasi Navare <manasi.d.navare@intel.com> wrote:
> On Tue, Sep 27, 2016 at 04:39:38PM +0300, Jani Nikula wrote:
>> On Mon, 26 Sep 2016, Jani Nikula <jani.nikula@linux.intel.com> wrote:
>> > On Fri, 16 Sep 2016, Manasi Navare <manasi.d.navare@intel.com> wrote:
>> >> While configuring the pipe during modeset, it should use
>> >> max clock and max lane count and reduce the bpp until
>> >> the requested mode rate is less than or equal to
>> >> available link BW.
>> >> This is required to pass DP Compliance.
>> >
>> > As I wrote in reply to patch 1/6, this is not a DP spec requirement. The
>> > link policy maker can freely choose the link parameters as long as the
>> > sink supports them.
>> 
>> Also double checked the DP link CTS spec. AFAICT none of the tests
>> expect the source to use the max clock or max lane count
>> directly. (Automated test request is another matter, and we should look
>> at it.)
>> 
>> I think patches 1-2 are based on an incorrect interpretation of the spec
>> and tests.
>> 
>> BR,
>> Jani.
>>
>
> I have the patches for handling the automated test request from DPR for
> compliance testing as mentioned in the CTS spec. But they have dependencies
> on these patches (1-6) so I will submit them after these get merged.

We need to re-evaluate the ordering of the patches.

BR,
Jani.

>
> Regards
> Manasi
>  
>> 
>> >
>> > BR,
>> > Jani.
>> >
>> >
>> >>
>> >> v3:
>> >> * Add Debug print if requested mode cannot be supported
>> >> during modeset (Dhinakaran Pandiyan)
>> >> v2:
>> >> * Removed the loop since we use max values of clock
>> >> and lane count (Dhinakaran Pandiyan)
>> >>
>> >> Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
>> >> ---
>> >>  drivers/gpu/drm/i915/intel_dp.c | 22 ++++++++--------------
>> >>  1 file changed, 8 insertions(+), 14 deletions(-)
>> >>
>> >> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
>> >> index d81c67cb..65b4559 100644
>> >> --- a/drivers/gpu/drm/i915/intel_dp.c
>> >> +++ b/drivers/gpu/drm/i915/intel_dp.c
>> >> @@ -1644,23 +1644,17 @@ intel_dp_compute_config(struct intel_encoder *encoder,
>> >>  	for (; bpp >= 6*3; bpp -= 2*3) {
>> >>  		mode_rate = intel_dp_link_required(adjusted_mode->crtc_clock,
>> >>  						   bpp);
>> >> +		clock = max_clock;
>> >> +		lane_count = max_lane_count;
>> >> +		link_clock = common_rates[clock];
>> >> +		link_avail = intel_dp_max_data_rate(link_clock,
>> >> +						    lane_count);
>> >>  
>> >> -		for (clock = min_clock; clock <= max_clock; clock++) {
>> >> -			for (lane_count = min_lane_count;
>> >> -				lane_count <= max_lane_count;
>> >> -				lane_count <<= 1) {
>> >> -
>> >> -				link_clock = common_rates[clock];
>> >> -				link_avail = intel_dp_max_data_rate(link_clock,
>> >> -								    lane_count);
>> >> -
>> >> -				if (mode_rate <= link_avail) {
>> >> -					goto found;
>> >> -				}
>> >> -			}
>> >> -		}
>> >> +		if (mode_rate <= link_avail)
>> >> +			goto found;
>> >>  	}
>> >>  
>> >> +	DRM_DEBUG_KMS("Requested Mode Rate not supported\n");
>> >>  	return false;
>> >>  
>> >>  found:
>> 
>> -- 
>> Jani Nikula, Intel Open Source Technology Center

-- 
Jani Nikula, Intel Open Source Technology Center
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