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

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

[Lyude Paul]

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 <lyude@redhat.com>
Fixes: fbc821c4a506 ("drm/mst: Support simultaneous down replies")
Cc: Wayne Lin <Wayne.Lin@amd.com>
Cc: Wayne Lin <waynelin@amd.com>
Cc: Sean Paul <seanpaul@chromium.org>
---
 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

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

[Sean Paul]

On Fri, Apr 3, 2020 at 4:03 PM Lyude Paul <lyude@redhat.com> 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 <lyude@redhat.com>
> Fixes: fbc821c4a506 ("drm/mst: Support simultaneous down replies")
> Cc: Wayne Lin <Wayne.Lin@amd.com>
> Cc: Wayne Lin <waynelin@amd.com>
> Cc: Sean Paul <seanpaul@chromium.org>

Thank you for fixing this

Reviewed-by: Sean Paul <sean@poorly.run>

> ---
>  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
>