Nouveau - Aug 2018 - [PATCH 4/5] drm/nouveau: add DisplayPort CEC-Tunneling-over-AUX support

From: Hans Verkuil <hans.verkuil at cisco.com>

Now that the DisplayPort CEC-Tunneling-over-AUX drm+i915 support
has been merged in the mainline kernel it is time to roll this
out to nouveau and amdgpu as well.

The first patch is required for this: it adds checks that the drm_dp_cec
functions are called with a working aux implementation. These checks
weren't necessary for the i915, but nouveau and amdgpu require them.

The next two patches update a comment in drm_dp_cec.c and fix a bug
in sideband AUX handling that I found while researching CEC Tunneling
over an MST hub. It's there to prevent others from stumbling over the
same bug in the future.

The fourth patch adds support for CEC to the nouveau driver.

The last patch adds support for CEC to the amdgpu driver. CEC is
only supported for the new DC modesetting code (thanks to Alex Deucher
for explaining this to me). I have no plans to add CEC support to the
old modesetting code (amd/amdgpu/dce*.c). If someone wants to, then
please contact me. I can't test this myself, but I can assist.

Changes since v1:

- Added Acks/Reviewed-by tags
- Removed a spurious non-functional change in patch 5 as pointed out by
  Harry Wentland.

Two notes on CEC-Tunneling-over-AUX:

1) You need to be very careful about which USB-C/DP/mini-DP to HDMI
   adapters you buy. Only a few support this feature correctly today.
   Known chipsets that support this are Parade PS175 & PS176 and
   MegaChips 2900. Unfortunately almost all Parade-based adapters
   do not hook up the HDMI CEC pin to the chip, making them useless
   for this. The Parade reference design was only recently changed
   to hook up this pin, so perhaps this situation will change for
   new Parade-based adapters.

   Adapters based on the new MegaChips 2900 fare much better: it
   appears that their reference design *does* hook up the CEC pin.
   Club3D has adapters using this device for USB-C, DP and mini-DP
   to HDMI, and they all work fine.

   If anyone finds other adapters that work besides those I list
   in https://hverkuil.home.xs4all.nl/cec-status.txt, please let
   me know and I'll add them to the list.

   Linux is the first OS that supports this feature, so I am
   not surprised that HW support for this has been poor. Hopefully
   this will change going forward. BTW, note the irony that CEC is
   now supported for DP-to-HDMI adapters, but not for the native
   HDMI ports on NVIDIA/AMD/Intel GPUs.

2) CEC-Tunneling does not work (yet?) if there is an MST hub in
   between. I'm still researching this but this might be a limitation 
   of MST.

Regards,

        Hans

PS: I've requested committer rights to drm-misc, so hopefully I can
commit this series myself.

Hans Verkuil (5):
  drm_dp_cec: check that aux has a transfer function
  drm_dp_cec: add note about good MegaChips 2900 CEC support
  drm_dp_mst_topology: fix broken
    drm_dp_sideband_parse_remote_dpcd_read()
  drm/nouveau: add DisplayPort CEC-Tunneling-over-AUX support
  drm/amdgpu: add DisplayPort CEC-Tunneling-over-AUX support

 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c  |  9 ++++++++-
 .../display/amdgpu_dm/amdgpu_dm_mst_types.c    |  2 ++
 drivers/gpu/drm/drm_dp_cec.c                   | 18 +++++++++++++++++-
 drivers/gpu/drm/drm_dp_mst_topology.c          |  1 +
 drivers/gpu/drm/nouveau/nouveau_connector.c    | 17 +++++++++++++++--
 5 files changed, 43 insertions(+), 4 deletions(-)

-- 
2.18.0

From: Hans Verkuil <hans.verkuil at cisco.com>

If aux->transfer == NULL, then just return without doing
anything. In that case the function is likely called for
a non-(e)DP connector.

This never happened for the i915 driver, but the nouveau and amdgpu
drivers need this check.

The alternative would be to add this check in those drivers before
every drm_dp_cec call, but it makes sense to check it in the
drm_dp_cec functions to prevent a kernel oops.

Signed-off-by: Hans Verkuil <hans.verkuil at cisco.com>
Reviewed-by: Lyude Paul <lyude at redhat.com>
Acked-by: Alex Deucher <alexander.deucher at amd.com>
---
 drivers/gpu/drm/drm_dp_cec.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/gpu/drm/drm_dp_cec.c b/drivers/gpu/drm/drm_dp_cec.c
index 988513346e9c..1407b13a8d5d 100644
--- a/drivers/gpu/drm/drm_dp_cec.c
+++ b/drivers/gpu/drm/drm_dp_cec.c
@@ -238,6 +238,10 @@ void drm_dp_cec_irq(struct drm_dp_aux *aux)
 	u8 cec_irq;
 	int ret;
 
+	/* No transfer function was set, so not a DP connector */
+	if (!aux->transfer)
+		return;
+
 	mutex_lock(&aux->cec.lock);
 	if (!aux->cec.adap)
 		goto unlock;
@@ -293,6 +297,10 @@ void drm_dp_cec_set_edid(struct drm_dp_aux *aux, const
struct edid *edid)
 	unsigned int num_las = 1;
 	u8 cap;
 
+	/* No transfer function was set, so not a DP connector */
+	if (!aux->transfer)
+		return;
+
 #ifndef CONFIG_MEDIA_CEC_RC
 	/*
 	 * CEC_CAP_RC is part of CEC_CAP_DEFAULTS, but it is stripped by
@@ -361,6 +369,10 @@ EXPORT_SYMBOL(drm_dp_cec_set_edid);
  */
 void drm_dp_cec_unset_edid(struct drm_dp_aux *aux)
 {
+	/* No transfer function was set, so not a DP connector */
+	if (!aux->transfer)
+		return;
+
 	cancel_delayed_work_sync(&aux->cec.unregister_work);
 
 	mutex_lock(&aux->cec.lock);
@@ -404,6 +416,8 @@ void drm_dp_cec_register_connector(struct drm_dp_aux *aux,
const char *name,
 				   struct device *parent)
 {
 	WARN_ON(aux->cec.adap);
+	if (WARN_ON(!aux->transfer))
+		return;
 	aux->cec.name = name;
 	aux->cec.parent = parent;
 	INIT_DELAYED_WORK(&aux->cec.unregister_work,
-- 
2.18.0

From: Hans Verkuil <hans.verkuil at cisco.com>

A big problem with DP CEC-Tunneling-over-AUX is that it is tricky
to find adapters with a chipset that supports this AND where the
manufacturer actually connected the HDMI CEC line to the chipset.

Add a mention of the MegaChips 2900 chipset which seems to support
this feature well.

Signed-off-by: Hans Verkuil <hans.verkuil at cisco.com>
Reviewed-by: Lyude Paul <lyude at redhat.com>
Acked-by: Alex Deucher <alexander.deucher at amd.com>
---
 drivers/gpu/drm/drm_dp_cec.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_dp_cec.c b/drivers/gpu/drm/drm_dp_cec.c
index 1407b13a8d5d..8a718f85079a 100644
--- a/drivers/gpu/drm/drm_dp_cec.c
+++ b/drivers/gpu/drm/drm_dp_cec.c
@@ -16,7 +16,9 @@
  * here. Quite a few active (mini-)DP-to-HDMI or USB-C-to-HDMI adapters
  * have a converter chip that supports CEC-Tunneling-over-AUX (usually the
  * Parade PS176), but they do not wire up the CEC pin, thus making CEC
- * useless.
+ * useless. Note that MegaChips 2900-based adapters appear to have good
+ * support for CEC tunneling. Those adapters that I have tested using
+ * this chipset all have the CEC line connected.
  *
  * Sadly there is no way for this driver to know this. What happens is
  * that a /dev/cecX device is created that is isolated and unable to see
-- 
2.18.0

From: Hans Verkuil <hans.verkuil at cisco.com>

When parsing the reply of a DP_REMOTE_DPCD_READ DPCD command the
result is wrong due to a missing idx increment.

This was never noticed since DP_REMOTE_DPCD_READ is currently not
used, but if you enable it, then it is all wrong.

Signed-off-by: Hans Verkuil <hans.verkuil at cisco.com>
Reviewed-by: Lyude Paul <lyude at redhat.com>
Acked-by: Alex Deucher <alexander.deucher at amd.com>
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c
b/drivers/gpu/drm/drm_dp_mst_topology.c
index 7780567aa669..5ff1d79b86c4 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -439,6 +439,7 @@ static bool drm_dp_sideband_parse_remote_dpcd_read(struct
drm_dp_sideband_msg_rx
 	if (idx > raw->curlen)
 		goto fail_len;
 	repmsg->u.remote_dpcd_read_ack.num_bytes = raw->msg[idx];
+	idx++;
 	if (idx > raw->curlen)
 		goto fail_len;
 
-- 
2.18.0

Add DisplayPort CEC-Tunneling-over-AUX support to nouveau.

Signed-off-by: Hans Verkuil <hans.verkuil at cisco.com>
Reviewed-by: Lyude Paul <lyude at redhat.com>
Acked-by: Alex Deucher <alexander.deucher at amd.com>
---
 drivers/gpu/drm/nouveau/nouveau_connector.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_connector.c
b/drivers/gpu/drm/nouveau/nouveau_connector.c
index 51932c72334e..eb4f766b5958 100644
--- a/drivers/gpu/drm/nouveau/nouveau_connector.c
+++ b/drivers/gpu/drm/nouveau/nouveau_connector.c
@@ -400,8 +400,10 @@ nouveau_connector_destroy(struct drm_connector *connector)
 	kfree(nv_connector->edid);
 	drm_connector_unregister(connector);
 	drm_connector_cleanup(connector);
-	if (nv_connector->aux.transfer)
+	if (nv_connector->aux.transfer) {
+		drm_dp_cec_unregister_connector(&nv_connector->aux);
 		drm_dp_aux_unregister(&nv_connector->aux);
+	}
 	kfree(connector);
 }

@@ -608,6 +610,7 @@ nouveau_connector_detect(struct drm_connector *connector,
bool force)

 		nouveau_connector_set_encoder(connector, nv_encoder);
 		conn_status = connector_status_connected;
+		drm_dp_cec_set_edid(&nv_connector->aux, nv_connector->edid);
 		goto out;
 	}

@@ -1108,11 +1111,14 @@ nouveau_connector_hotplug(struct nvif_notify *notify)

 	if (rep->mask & NVIF_NOTIFY_CONN_V0_IRQ) {
 		NV_DEBUG(drm, "service %s\n", name);
+		drm_dp_cec_irq(&nv_connector->aux);
 		if ((nv_encoder = find_encoder(connector, DCB_OUTPUT_DP)))
 			nv50_mstm_service(nv_encoder->dp.mstm);
 	} else {
 		bool plugged = (rep->mask != NVIF_NOTIFY_CONN_V0_UNPLUG);

+		if (!plugged)
+			drm_dp_cec_unset_edid(&nv_connector->aux);
 		NV_DEBUG(drm, "%splugged %s\n", plugged ? "" :
"un", name);
 		if ((nv_encoder = find_encoder(connector, DCB_OUTPUT_DP))) {
 			if (!plugged)
@@ -1302,7 +1308,6 @@ nouveau_connector_create(struct drm_device *dev, int
index)
 			kfree(nv_connector);
 			return ERR_PTR(ret);
 		}
-
 		funcs = &nouveau_connector_funcs;
 		break;
 	default:
@@ -1356,6 +1361,14 @@ nouveau_connector_create(struct drm_device *dev, int
index)
 		break;
 	}

+	switch (type) {
+	case DRM_MODE_CONNECTOR_DisplayPort:
+	case DRM_MODE_CONNECTOR_eDP:
+		drm_dp_cec_register_connector(&nv_connector->aux,
+					      connector->name, dev->dev);
+		break;
+	}
+
 	ret = nvif_notify_init(&disp->disp.object, nouveau_connector_hotplug,
 			       true, NV04_DISP_NTFY_CONN,
 			       &(struct nvif_notify_conn_req_v0) {
-- 
2.18.0

When parsing the reply of a DP_REMOTE_DPCD_READ DPCD command the
result is wrong due to a missing idx increment.

This was never noticed since DP_REMOTE_DPCD_READ is currently not
used, but if you enable it, then it is all wrong.

Signed-off-by: Hans Verkuil <hans.verkuil at cisco.com>
Reviewed-by: Lyude Paul <lyude at redhat.com>
Acked-by: Alex Deucher <alexander.deucher at amd.com>
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c
b/drivers/gpu/drm/drm_dp_mst_topology.c
index 7780567aa669..5ff1d79b86c4 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -439,6 +439,7 @@ static bool drm_dp_sideband_parse_remote_dpcd_read(struct
drm_dp_sideband_msg_rx
 	if (idx > raw->curlen)
 		goto fail_len;
 	repmsg->u.remote_dpcd_read_ack.num_bytes = raw->msg[idx];
+	idx++;
 	if (idx > raw->curlen)
 		goto fail_len;

-- 
2.18.0

Sorry, this v2 patch series is a bit messy: my git-send-email failed at patch 3
for some reason, so I posted patches 3-5 manually, but I forgot to add
'v2' to the
subject of patch 4/5 and for some reason patch 3 now appeared twice. The
contents
of the patches is correct, though :-)

Regards,

	Hans