[PATCH v2] drm: add dp helper to initialize remote aux channel.

[David (Dingchen) Zhang]

[why]
We need to minimally initialize the remote aux channel, e.g. the
crc work struct of remote aux to dump the sink's DPRX CRCs in MST
setup.

[how]
Add helper that only initializes the crc work struct of the remote
aux, hooke crc work queue to 'drm_dp_aux_crc_work'. Then call this
helper in DP MST port initialization.
This, plus David Francis' patch [1], fix the issue of MST remote
aux DPCD CRCs read.

[1] https://patchwork.kernel.org/patch/11217941/

Cc: Leo Li <sunpeng.li at amd.com>
Cc: Harry Wentland <Harry.Wentland at amd.com>
Signed-off-by: David (Dingchen) Zhang <dingchen.zhang at amd.com>
---
 drivers/gpu/drm/drm_dp_helper.c       | 13 +++++++++++++
 drivers/gpu/drm/drm_dp_mst_topology.c |  3 +++
 include/drm/drm_dp_helper.h           |  1 +
 3 files changed, 17 insertions(+)

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 2c7870aef469..cc4845d0fcb8 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -968,6 +968,19 @@ static void drm_dp_aux_crc_work(struct work_struct *work)
 	}
 }
 
+/**
+ * drm_dp_remote_aux_init() - minimally initialise a remote aux channel
+ * @aux: DisplayPort AUX channel
+ *
+ * Used for remote aux channel in general. Merely initialize the crc work
+ * struct.
+ */
+void drm_dp_remote_aux_init(struct drm_dp_aux *aux)
+{
+	INIT_WORK(&aux->crc_work, drm_dp_aux_crc_work);
+}
+EXPORT_SYMBOL(drm_dp_remote_aux_init);
+
 /**
  * drm_dp_aux_init() - minimally initialise an aux channel
  * @aux: DisplayPort AUX channel
diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 87fc44895d83..edafa182264a 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -1945,6 +1945,9 @@ drm_dp_mst_handle_link_address_port(struct drm_dp_mst_branch *mstb,
 		port->aux.dev = dev->dev;
 		port->aux.is_remote = true;
 
+		/* initialize the MST downstream port's AUX crc work queue */
+		drm_dp_remote_aux_init(&port->aux);
+
 		/*
 		 * Make sure the memory allocation for our parent branch stays
 		 * around until our own memory allocation is released
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index 8f8f3632e697..b2e6923d5929 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -1465,6 +1465,7 @@ int drm_dp_downstream_id(struct drm_dp_aux *aux, char id[6]);
 void drm_dp_downstream_debug(struct seq_file *m, const u8 dpcd[DP_RECEIVER_CAP_SIZE],
 			     const u8 port_cap[4], struct drm_dp_aux *aux);
 
+void drm_dp_remote_aux_init(struct drm_dp_aux *aux);
 void drm_dp_aux_init(struct drm_dp_aux *aux);
 int drm_dp_aux_register(struct drm_dp_aux *aux);
 void drm_dp_aux_unregister(struct drm_dp_aux *aux);
-- 
2.17.1