From: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
To: Lyude Paul <lyude@redhat.com>
Cc: Sean Paul <seanpaul@google.com>, David Airlie <airlied@linux.ie>,
nouveau@lists.freedesktop.org, linux-kernel@vger.kernel.org,
amd-gfx@lists.freedesktop.org,
Hans de Goede <hdegoede@redhat.com>,
dri-devel@lists.freedesktop.org,
Thomas Zimmermann <tzimmermann@suse.de>,
Alex Deucher <alexander.deucher@amd.com>,
Mikita Lipski <mikita.lipski@amd.com>
Subject: Re: [PATCH 2/3] drm/dp_mst: Don't show connectors as connected before probing available PBN
Date: Thu, 5 Mar 2020 15:11:19 +0200 [thread overview]
Message-ID: <20200305131119.GJ13686@intel.com> (raw)
In-Reply-To: <20200304223614.312023-3-lyude@redhat.com>
On Wed, Mar 04, 2020 at 05:36:12PM -0500, Lyude Paul wrote:
> It's next to impossible for us to do connector probing on topologies
> without occasionally racing with userspace, since creating a connector
> itself causes a hotplug event which we have to send before probing the
> available PBN of a connector. Even if we didn't have this hotplug event
> sent, there's still always a chance that userspace started probing
> connectors before we finished probing the topology.
>
> This can be a problem when validating a new MST state since the
> connector will be shown as connected briefly, but without any available
> PBN - causing any atomic state which would enable said connector to fail
> with -ENOSPC. So, let's simply workaround this by telling userspace new
> MST connectors are disconnected until we've finished probing their PBN.
> Since we always send a hotplug event at the end of the link address
> probing process, userspace will still know to reprobe the connector when
> we're ready.
>
> Signed-off-by: Lyude Paul <lyude@redhat.com>
> Fixes: cd82d82cbc04 ("drm/dp_mst: Add branch bandwidth validation to MST atomic check")
> Cc: Mikita Lipski <mikita.lipski@amd.com>
> Cc: Alex Deucher <alexander.deucher@amd.com>
> Cc: Sean Paul <seanpaul@google.com>
> Cc: Hans de Goede <hdegoede@redhat.com>
> ---
> drivers/gpu/drm/drm_dp_mst_topology.c | 13 +++++++++++++
> 1 file changed, 13 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
> index 207eef08d12c..7b0ff0cff954 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -4033,6 +4033,19 @@ drm_dp_mst_detect_port(struct drm_connector *connector,
> ret = connector_status_connected;
> break;
> }
> +
> + /* We don't want to tell userspace the port is actually plugged into
> + * anything until we've finished probing it's available_pbn, otherwise
"its"
Why is the connector even registered before we've finished the probe?
> + * userspace will see racy atomic check failures
> + *
> + * Since we always send a hotplug at the end of probing topology
> + * state, we can just let userspace reprobe this connector later.
> + */
> + if (ret == connector_status_connected && !port->available_pbn) {
> + DRM_DEBUG_KMS("[CONNECTOR:%d:%s] not ready yet (PBN not probed)\n",
> + connector->base.id, connector->name);
> + ret = connector_status_disconnected;
> + }
> out:
> drm_dp_mst_topology_put_port(port);
> return ret;
> --
> 2.24.1
>
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
--
Ville Syrjälä
Intel
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel
next prev parent reply other threads:[~2020-03-05 13:11 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-04 22:36 [PATCH 0/3] drm/dp_mst: Fix bandwidth checking regressions from DSC patches Lyude Paul
2020-03-04 22:36 ` [PATCH 1/3] drm/dp_mst: Rename drm_dp_mst_is_dp_mst_end_device() to be less redundant Lyude Paul
2020-03-04 22:36 ` [PATCH 2/3] drm/dp_mst: Don't show connectors as connected before probing available PBN Lyude Paul
2020-03-05 13:11 ` Ville Syrjälä [this message]
2020-03-05 18:13 ` Lyude Paul
2020-03-05 18:29 ` Ville Syrjälä
2020-03-05 18:52 ` Lyude Paul
2020-03-05 19:44 ` Lyude Paul
2020-03-06 20:03 ` Lyude Paul
2020-03-06 21:22 ` Lyude Paul
2020-03-04 22:36 ` [PATCH 3/3] drm/dp_mst: Rewrite and fix bandwidth limit checks Lyude Paul
2020-03-05 16:41 ` [PATCH 0/3] drm/dp_mst: Fix bandwidth checking regressions from DSC patches Hans de Goede
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200305131119.GJ13686@intel.com \
--to=ville.syrjala@linux.intel.com \
--cc=airlied@linux.ie \
--cc=alexander.deucher@amd.com \
--cc=amd-gfx@lists.freedesktop.org \
--cc=dri-devel@lists.freedesktop.org \
--cc=hdegoede@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=lyude@redhat.com \
--cc=mikita.lipski@amd.com \
--cc=nouveau@lists.freedesktop.org \
--cc=seanpaul@google.com \
--cc=tzimmermann@suse.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).