2020-04-03 20:05:45

by Lyude Paul

Subject: [PATCH] drm/dp_mst: Don't drop NAKs for down responses

It looks like that when we introduced the ability to handle multiple
down requests at once, we accidentally started dropping NAK replies -
causing sideband messages which got NAK'd to seemingly timeout and cause
all sorts of weirdness.

So, fix this by making sure we don't return from
drm_dp_mst_handle_down_rep() early, but instead treat NAKs like any
other message.

Signed-off-by: Lyude Paul <[email protected]>
Fixes: fbc821c4a506 ("drm/mst: Support simultaneous down replies")
Cc: Wayne Lin <[email protected]>
Cc: Wayne Lin <[email protected]>
Cc: Sean Paul <[email protected]>
---
drivers/gpu/drm/drm_dp_mst_topology.c | 1 -
1 file changed, 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 10d0315af513..5449ada3e019 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -3813,7 +3813,6 @@ static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr)
txmsg->reply.u.nak.reason,
drm_dp_mst_nak_reason_str(txmsg->reply.u.nak.reason),
txmsg->reply.u.nak.nak_data);
- goto out_clear_reply;
}

memset(msg, 0, sizeof(struct drm_dp_sideband_msg_rx));
--
2.25.1

2020-04-06 19:52:13

by Sean Paul

Subject: Re: [PATCH] drm/dp_mst: Don't drop NAKs for down responses

On Fri, Apr 3, 2020 at 4:03 PM Lyude Paul <[email protected]> wrote:
>
> It looks like that when we introduced the ability to handle multiple
> down requests at once, we accidentally started dropping NAK replies -
> causing sideband messages which got NAK'd to seemingly timeout and cause
> all sorts of weirdness.
>
> So, fix this by making sure we don't return from
> drm_dp_mst_handle_down_rep() early, but instead treat NAKs like any
> other message.
>
> Signed-off-by: Lyude Paul <[email protected]>
> Fixes: fbc821c4a506 ("drm/mst: Support simultaneous down replies")
> Cc: Wayne Lin <[email protected]>
> Cc: Wayne Lin <[email protected]>
> Cc: Sean Paul <[email protected]>

Thank you for fixing this

Reviewed-by: Sean Paul <[email protected]>

> ---
> drivers/gpu/drm/drm_dp_mst_topology.c | 1 -
> 1 file changed, 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
> index 10d0315af513..5449ada3e019 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -3813,7 +3813,6 @@ static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr)
> txmsg->reply.u.nak.reason,
> drm_dp_mst_nak_reason_str(txmsg->reply.u.nak.reason),
> txmsg->reply.u.nak.nak_data);
> - goto out_clear_reply;
> }
>
> memset(msg, 0, sizeof(struct drm_dp_sideband_msg_rx));
> --
> 2.25.1
>