linux-kernel - Re: [Intel-gfx] [PATCH 3/7] drm/i915: Treat PCH eDP like DP in most places

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Date:	Wed, 02 Nov 2011 14:13:12 -0700
From:	Keith Packard <keithp@...thp.com>
To:	Adam Jackson <ajax@...hat.com>
Cc:	Jesse Barnes <jbarnes@...tuousgeek.org>,
	intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	dri-devel@...ts.freedesktop.org
Subject: Re: [Intel-gfx] [PATCH 3/7] drm/i915: Treat PCH eDP like DP in most places

On Wed, 02 Nov 2011 16:35:51 -0400, Adam Jackson <ajax@...hat.com> wrote:

> It is?  The DP 1.1a text for lane count is "For Rev.1.1, only the 
> following three values are supported. All other values are reserved."

Yeah, if you look at the MAX_LINK_RATE field, we assume that it has a
useful value. I'll bet they were thinking of letting the spec support
things like alternate clock rates or 3 lanes or something, and the 1.1
version just tied things down to allow only sensible values there.

How about we just always use the DPCD value?

commit e0fafa5dee031ef6174eadb005a5f01d13da931d
Author: Keith Packard <keithp@...thp.com>
Date:   Wed Nov 2 13:03:47 2011 -0700

    drm/i915: Use DPCD value for max DP lanes.
    
    The BIOS VBT value for an eDP panel has been shown to be incorrect on
    one machine, and we haven't found any machines where the DPCD value
    was wrong, so we'll use the DPCD value everywhere.
    
    Signed-off-by: Keith Packard <keithp@...thp.com>

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 02b56ce..5056d29 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -154,16 +154,12 @@ intel_edp_link_config(struct intel_encoder *intel_encoder,
 static int
 intel_dp_max_lane_count(struct intel_dp *intel_dp)
 {
-       int max_lane_count = 4;
-
-       if (intel_dp->dpcd[DP_DPCD_REV] >= 0x11) {
-               max_lane_count = intel_dp->dpcd[DP_MAX_LANE_COUNT] & 0x1f;
-               switch (max_lane_count) {
-               case 1: case 2: case 4:
-                       break;
-               default:
-                       max_lane_count = 4;
-               }
+       int max_lane_count = intel_dp->dpcd[DP_MAX_LANE_COUNT] & 0x1f;
+       switch (max_lane_count) {
+       case 1: case 2: case 4:
+               break;
+       default:
+               max_lane_count = 4;
        }
        return max_lane_count;
 }
@@ -765,12 +761,11 @@ intel_dp_set_m_n(struct drm_crtc *crtc, struct drm_display_mode *mode,
                        continue;
 
                intel_dp = enc_to_intel_dp(encoder);
-               if (intel_dp->base.type == INTEL_OUTPUT_DISPLAYPORT || is_pch_edp(intel_dp)) {
+               if (intel_dp->base.type == INTEL_OUTPUT_DISPLAYPORT ||
+                   intel_dp->base.type == INTEL_OUTPUT_EDP)
+               {
                        lane_count = intel_dp->lane_count;
                        break;
-               } else if (is_cpu_edp(intel_dp)) {
-                       lane_count = dev_priv->edp.lanes;
-                       break;
                }
        }

-- 
keith.packard@...el.com

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