[Intel-gfx] [PATCH] Revert "drm/i915: reverse dp link param selection, prefer fast over wide again"

[Daniel Vetter]

On Mon, Jul 14, 2014 at 11:04:39AM +1000, Dave Airlie wrote:
> From: Dave Airlie <airlied at redhat.com>
> 
> This reverts commit 38aecea0ccbb909d635619cba22f1891e589b434.
> 
> This breaks Haswell Thinkpad + Lenovo dock in SST mode with a HDMI monitor attached.
> 
> Before this we can 1920x1200 mode, after this we only ever get 1024x768, and
> a lot of deferring.
> 
> This didn't revert clean, but this should be fine.
> 
> bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1117008
> Cc: stable at vger.kernel.org # v3.15
> Signed-off-by: Dave Airlie <airlied at redhat.com>

Ugh, painful. Iirc your revert here wins on first-regression grounds, but
I'd like to first try whether we can do better.

Paulo, can you please take a look? Iirc it's a hsw, but I guess Dave can
throw logs at you.
-Daniel

> ---
>  drivers/gpu/drm/i915/intel_dp.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 2a00cb8..61963d3 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -833,8 +833,8 @@ intel_dp_compute_config(struct intel_encoder *encoder,
>  		mode_rate = intel_dp_link_required(adjusted_mode->crtc_clock,
>  						   bpp);
>  
> -		for (lane_count = min_lane_count; lane_count <= max_lane_count; lane_count <<= 1) {
> -			for (clock = min_clock; clock <= max_clock; clock++) {
> +		for (clock = min_clock; clock <= max_clock; clock++) {
> +			for (lane_count = min_lane_count; lane_count <= max_lane_count; lane_count <<= 1) {
>  				link_clock = drm_dp_bw_code_to_link_rate(bws[clock]);
>  				link_avail = intel_dp_max_data_rate(link_clock,
>  								    lane_count);
> -- 
> 1.9.3
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch