On Fri, Feb 14, 2020 at 12:58 AM Lin, Wayne <Wayne.Lin@xxxxxxx> wrote:
>
> [AMD Public Use]
>
> Hi Paul,
>
> Thanks for the mail!
>
> I tried to solve this problem by having restriction on sending one msg at a time due to hub/dock compatibility problems.
> From my experience, some branch devices don't handle well on interleaved replies (Dock from HP I think)
Hi Wayne,
Hmm, that's interesting, do you have a part number of the failing dock
so I can test it?
> As the result of that, correct me if I'm wrong, I remember most gpu vendors just send one down request at a time now in windows environment.
> I would suggest the original solution :)
I can't really say what happens on the Windows side of the world, but
I suppose that makes sense if this is a widespread issue with docks. I
do worry about the performance hit.
If indeed this is a problem, could we ratelimit per branch device
instead of globally? Even that would be better than serializing
everything.
Sean
>
> Thanks!
> > -----Original Message-----
> > From: Sean Paul <sean@xxxxxxxxxx>
> > Sent: Friday, February 14, 2020 5:15 AM
> > To: dri-devel@xxxxxxxxxxxxxxxxxxxxx
> > Cc: lyude@xxxxxxxxxx; Lin, Wayne <Wayne.Lin@xxxxxxx>; Sean Paul
> > <seanpaul@xxxxxxxxxxxx>; Maarten Lankhorst
> > <maarten.lankhorst@xxxxxxxxxxxxxxx>; Maxime Ripard <mripard@xxxxxxxxxx>;
> > David Airlie <airlied@xxxxxxxx>
> > Subject: [PATCH 3/3] drm/dp_mst: Remove single tx msg restriction.
> >
> > From: Sean Paul <seanpaul@xxxxxxxxxxxx>
> >
> > Now that we can support multiple simultaneous replies, remove the
> > restrictions placed on sending new tx msgs.
> >
> > This patch essentially just reverts commit
> > 5a64967a2f3b ("drm/dp_mst: Have DP_Tx send one msg at a time") now
> > that the problem is solved in a different way.
> >
> > Cc: Wayne Lin <Wayne.Lin@xxxxxxx>
> > Signed-off-by: Sean Paul <seanpaul@xxxxxxxxxxxx>
> > ---
> > drivers/gpu/drm/drm_dp_mst_topology.c | 14 ++------------
> > include/drm/drm_dp_mst_helper.h | 6 ------
> > 2 files changed, 2 insertions(+), 18 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c
> > b/drivers/gpu/drm/drm_dp_mst_topology.c
> > index 7e6a82efdfc02..cbf0bb0ddeb84 100644
> > --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> > +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> > @@ -1203,8 +1203,6 @@ static int drm_dp_mst_wait_tx_reply(struct
> > drm_dp_mst_branch *mstb,
> > txmsg->state == DRM_DP_SIDEBAND_TX_SENT) {
> > mstb->tx_slots[txmsg->seqno] = NULL;
> > }
> > - mgr->is_waiting_for_dwn_reply = false;
> > -
> > }
> > out:
> > if (unlikely(ret == -EIO) && drm_debug_enabled(DRM_UT_DP)) { @@
> > -1214,7 +1212,6 @@ static int drm_dp_mst_wait_tx_reply(struct
> > drm_dp_mst_branch *mstb,
> > }
> > mutex_unlock(&mgr->qlock);
> >
> > - drm_dp_mst_kick_tx(mgr);
> > return ret;
> > }
> >
> > @@ -2797,11 +2794,9 @@ static void process_single_down_tx_qlock(struct
> > drm_dp_mst_topology_mgr *mgr)
> > ret = process_single_tx_qlock(mgr, txmsg, false);
> > if (ret == 1) {
> > /* txmsg is sent it should be in the slots now */
> > - mgr->is_waiting_for_dwn_reply = true;
> > list_del(&txmsg->next);
> > } else if (ret) {
> > DRM_DEBUG_KMS("failed to send msg in q %d\n", ret);
> > - mgr->is_waiting_for_dwn_reply = false;
> > list_del(&txmsg->next);
> > if (txmsg->seqno != -1)
> > txmsg->dst->tx_slots[txmsg->seqno] = NULL; @@ -2841,8
> > +2836,7 @@ static void drm_dp_queue_down_tx(struct
> > drm_dp_mst_topology_mgr *mgr,
> > drm_dp_mst_dump_sideband_msg_tx(&p, txmsg);
> > }
> >
> > - if (list_is_singular(&mgr->tx_msg_downq) &&
> > - !mgr->is_waiting_for_dwn_reply)
> > + if (list_is_singular(&mgr->tx_msg_downq))
> > process_single_down_tx_qlock(mgr);
> > mutex_unlock(&mgr->qlock);
> > }
> > @@ -3822,7 +3816,6 @@ static int drm_dp_mst_handle_down_rep(struct
> > drm_dp_mst_topology_mgr *mgr)
> > mutex_lock(&mgr->qlock);
> > txmsg->state = DRM_DP_SIDEBAND_TX_RX;
> > mstb->tx_slots[seqno] = NULL;
> > - mgr->is_waiting_for_dwn_reply = false;
> > mutex_unlock(&mgr->qlock);
> >
> > wake_up_all(&mgr->tx_waitq);
> > @@ -3830,9 +3823,6 @@ static int drm_dp_mst_handle_down_rep(struct
> > drm_dp_mst_topology_mgr *mgr)
> > return 0;
> >
> > out_clear_reply:
> > - mutex_lock(&mgr->qlock);
> > - mgr->is_waiting_for_dwn_reply = false;
> > - mutex_unlock(&mgr->qlock);
> > if (msg)
> > memset(msg, 0, sizeof(struct drm_dp_sideband_msg_rx));
> > out:
> > @@ -4670,7 +4660,7 @@ static void drm_dp_tx_work(struct work_struct
> > *work)
> > struct drm_dp_mst_topology_mgr *mgr = container_of(work, struct
> > drm_dp_mst_topology_mgr, tx_work);
> >
> > mutex_lock(&mgr->qlock);
> > - if (!list_empty(&mgr->tx_msg_downq)
> > && !mgr->is_waiting_for_dwn_reply)
> > + if (!list_empty(&mgr->tx_msg_downq))
> > process_single_down_tx_qlock(mgr);
> > mutex_unlock(&mgr->qlock);
> > }
> > diff --git a/include/drm/drm_dp_mst_helper.h
> > b/include/drm/drm_dp_mst_helper.h index 7d0341f94ce1b..fcc30e64c8e7e
> > 100644
> > --- a/include/drm/drm_dp_mst_helper.h
> > +++ b/include/drm/drm_dp_mst_helper.h
> > @@ -619,12 +619,6 @@ struct drm_dp_mst_topology_mgr {
> > * &drm_dp_sideband_msg_tx.state once they are queued
> > */
> > struct mutex qlock;
> > -
> > - /**
> > - * @is_waiting_for_dwn_reply: indicate whether is waiting for down
> > reply
> > - */
> > - bool is_waiting_for_dwn_reply;
> > -
> > /**
> > * @tx_msg_downq: List of pending down replies.
> > */
> > --
> > Sean Paul, Software Engineer, Google / Chromium OS
> --
> Wayne Lin
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