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From: Lyude Paul <lyude@redhat.com>
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Date: Fri, 24 Apr 2020 15:07:22 -0400
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Subject: drm/dp_mst: Fix drm_dp_send_dpcd_write() return code
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drm_dp_mst_wait_tx_reply() returns > 1 if time elapsed in
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wait_event_timeout() before check_txmsg_state(mgr, txmsg) evaluated to
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true. However, we make the mistake of returning this time from
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drm_dp_send_dpcd_write() on success instead of returning the number of
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bytes written - causing spontaneous failures during link probing:
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[drm:drm_dp_send_link_address [drm_kms_helper]] *ERROR* GUID check on
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10:01 failed: 3975
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Yikes! So, fix this by returning the number of bytes written on success
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instead.
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Signed-off-by: Lyude Paul <lyude@redhat.com>
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Fixes: cb897542c6d2 ("drm/dp_mst: Fix W=1 warnings")
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Cc: Benjamin Gaignard <benjamin.gaignard@st.com>
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Cc: Sean Paul <sean@poorly.run>
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Acked-by: Alex Deucher <alexander.deucher@amd.com>
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Reviewed-by: Sean Paul <sean@poorly.run>
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Link: https://patchwork.freedesktop.org/patch/msgid/20200424190722.775284-1-lyude@redhat.com
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---
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drivers/gpu/drm/drm_dp_mst_topology.c | 8 ++++++--
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1 file changed, 6 insertions(+), 2 deletions(-)
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diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
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index 03a1496f6120..21dc78cb4ba6 100644
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--- a/drivers/gpu/drm/drm_dp_mst_topology.c
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+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
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@@ -3436,8 +3436,12 @@ static int drm_dp_send_dpcd_write(struct drm_dp_mst_topology_mgr *mgr,
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drm_dp_queue_down_tx(mgr, txmsg);
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ret = drm_dp_mst_wait_tx_reply(mstb, txmsg);
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- if (ret > 0 && txmsg->reply.reply_type == DP_SIDEBAND_REPLY_NAK)
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- ret = -EIO;
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+ if (ret > 0) {
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+ if (txmsg->reply.reply_type == DP_SIDEBAND_REPLY_NAK)
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+ ret = -EIO;
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+ else
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+ ret = size;
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+ }
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kfree(txmsg);
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fail_put:
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