linux-kernel - [RFC 05/20] drm/nouveau/kms: Don't clear DP_MST_CTRL DPCD in nv50_mstm

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Message-Id: <20200811200457.134743-6-lyude@redhat.com>
Date:   Tue, 11 Aug 2020 16:04:42 -0400
From:   Lyude Paul <lyude@...hat.com>
To:     nouveau@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org
Cc:     Ben Skeggs <bskeggs@...hat.com>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Dave Airlie <airlied@...il.com>,
        Pankaj Bharadiya <pankaj.laxminarayan.bharadiya@...el.com>,
        Alex Deucher <alexander.deucher@....com>,
        Takashi Iwai <tiwai@...e.de>, James Jones <jajones@...dia.com>,
        linux-kernel@...r.kernel.org (open list)
Subject: [RFC 05/20] drm/nouveau/kms: Don't clear DP_MST_CTRL DPCD in nv50_mstm_new()

Since fa3cdf8d0b09 ("drm/nouveau: Reset MST branching unit before
enabling") we've been clearing DP_MST_CTRL before we start enabling MST.
Since then clearing DP_MST_CTRL in nv50_mstm_new() has been unnecessary
and redundant, so let's remove it.

Signed-off-by: Lyude Paul <lyude@...hat.com>
Reviewed-by: Ben Skeggs <bskeggs@...hat.com>
---
 drivers/gpu/drm/nouveau/dispnv50/disp.c | 11 -----------
 1 file changed, 11 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/dispnv50/disp.c b/drivers/gpu/drm/nouveau/dispnv50/disp.c
index e7874877da858..c4d138f0ca054 100644
--- a/drivers/gpu/drm/nouveau/dispnv50/disp.c
+++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c
@@ -1535,17 +1535,6 @@ nv50_mstm_new(struct nouveau_encoder *outp, struct drm_dp_aux *aux, int aux_max,
 	struct drm_device *dev = outp->base.base.dev;
 	struct nv50_mstm *mstm;
 	int ret;
-	u8 dpcd;
-
-	/* This is a workaround for some monitors not functioning
-	 * correctly in MST mode on initial module load.  I think
-	 * some bad interaction with the VBIOS may be responsible.
-	 *
-	 * A good ol' off and on again seems to work here ;)
-	 */
-	ret = drm_dp_dpcd_readb(aux, DP_DPCD_REV, &dpcd);
-	if (ret >= 0 && dpcd >= 0x12)
-		drm_dp_dpcd_writeb(aux, DP_MSTM_CTRL, 0);
 
 	if (!(mstm = *pmstm = kzalloc(sizeof(*mstm), GFP_KERNEL)))
 		return -ENOMEM;
-- 
2.26.2