[Intel-gfx] [PATCH 12/14] drm/i915: Reverse the loop in intel_dp_compute_config

[Pandiyan, Dhinakaran]

On Thu, 2016-09-01 at 15:08 -0700, Manasi Navare wrote:
> While configuring the pipe during modeset, it should loop
> starting from max clock and max lane count reducing the
> lane count and clock in each iteration until the requested mode
> rate is less than or equal to available link BW.
> 
> Signed-off-by: Manasi Navare <manasi.d.navare at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index dfdbe65..e094b25 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -1552,11 +1552,10 @@ 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);
> -
> -		for (clock = min_clock; clock <= max_clock; clock++) {
> -			for (lane_count = min_lane_count;
> -				lane_count <= max_lane_count;
> -				lane_count <<= 1) {
> +		for (clock = max_clock; clock >= max_clock; clock--) {
> +			for (lane_count = max_lane_count;
> +			     lane_count >= min_lane_count;
> +			     lane_count >>= 1) {
>  
>  				link_clock = common_rates[clock];
>  				link_avail = intel_dp_max_data_rate(link_clock,


I don't understand why the loop is still here? We are starting with the
max.link rate and max.lane count. If that is not good enough for the
mode rate, then lowering link bandwidth won't help.