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drm/dp/mst: Handle invalid link bandwidth from DPCD gracefully

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Don't BUG out if the link reports an invalid (or plain unknown)
bandwidth value, but report the failure and fail gracefully.

Fixes a trivial compiler warning in case the BUG is ever compiled away.

Link: http://lkml.kernel.org/p/1415785566-12758-1-git-send-email-geert@linux-m68k.org
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Dave Airlie <airlied@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
This commit is contained in:
Chris Wilson 2014-11-12 10:13:37 +00:00 committed by Dave Airlie
parent db88362884
commit b853fdb3c0
1 changed files with 22 additions and 6 deletions
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28
drivers/gpu/drm/drm_dp_mst_topology.c
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@ -1799,17 +1799,27 @@ static int drm_dp_send_up_ack_reply(struct drm_dp_mst_topology_mgr *mgr,
return 0;
}
static int drm_dp_get_vc_payload_bw(int dp_link_bw, int dp_link_count)
static bool drm_dp_get_vc_payload_bw(int dp_link_bw,
int dp_link_count,
int *out)
{
switch (dp_link_bw) {
default:
DRM_DEBUG_KMS("invalid link bandwidth in DPCD: %x (link count: %d)\n",
dp_link_bw, dp_link_count);
return false;
case DP_LINK_BW_1_62:
return 3 * dp_link_count;
*out = 3 * dp_link_count;
break;
case DP_LINK_BW_2_7:
return 5 * dp_link_count;
*out = 5 * dp_link_count;
break;
case DP_LINK_BW_5_4:
return 10 * dp_link_count;
*out = 10 * dp_link_count;
break;
}
BUG();
return true;
}
/**
@ -1841,7 +1851,13 @@ int drm_dp_mst_topology_mgr_set_mst(struct drm_dp_mst_topology_mgr *mgr, bool ms
goto out_unlock;
}
mgr->pbn_div = drm_dp_get_vc_payload_bw(mgr->dpcd[1], mgr->dpcd[2] & DP_MAX_LANE_COUNT_MASK);
if (!drm_dp_get_vc_payload_bw(mgr->dpcd[1],
mgr->dpcd[2] & DP_MAX_LANE_COUNT_MASK,
&mgr->pbn_div)) {
ret = -EINVAL;
goto out_unlock;
}
mgr->total_pbn = 2560;
mgr->total_slots = DIV_ROUND_UP(mgr->total_pbn, mgr->pbn_div);
mgr->avail_slots = mgr->total_slots;