From 3ecd2a97a7cffa0aabc95ce9ad46e3a99ce4a422 Mon Sep 17 00:00:00 2001
From: "David (Dingchen) Zhang" <dingchen.zhang@amd.com>
Date: Fri, 6 Dec 2019 17:56:37 -0500
Subject: drm: add dp helper to initialize remote aux channel.
Git-commit: c908b1c4bb56c27fa6fbb48e2d3dbebdad366706
Patch-mainline: v5.6-rc1
References: jsc#SLE-12680, jsc#SLE-12880, jsc#SLE-12882, jsc#SLE-12883, jsc#SLE-13496, jsc#SLE-15322

[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@amd.com>
Cc: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: David (Dingchen) Zhang <dingchen.zhang@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Patrik Jakobsson <pjakobsson@suse.de>
---
 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 374cedc6c2ac..a5364b5192b8 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -978,6 +978,19 @@ 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 732ff75d43cf..3d12416f0285 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -2219,6 +2219,9 @@ drm_dp_mst_add_port(struct drm_device *dev,
 	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 0aeaf4a8951c..bc04467f7c3a 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);
-- 
2.28.0