drm/amd: Drop debugfs access to the DPCD

There is already access to the DPCD from userspace through
`CONFIG_DRM_DP_AUX_CHARDEV`, so it's unnecessary to reinvent the wheel
with a set of extra debugfs nodes specific to amdgpu.

The character device interface behaves more like you would expect in that
you can seek/read/write all from the same file.
Reviewed-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h

@@ -661,10 +661,6 @@ struct amdgpu_dm_connector {
 	struct mutex hpd_lock;
 
 	bool fake_enable;
-#ifdef CONFIG_DEBUG_FS
-	uint32_t debugfs_dpcd_address;
-	uint32_t debugfs_dpcd_size;
-#endif
 	bool force_yuv420_output;
 	struct dsc_preferred_settings dsc_settings;
 	union dp_downstream_port_present mst_downstream_port_present;

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_debugfs.c

@@ -1039,88 +1039,6 @@ static ssize_t dp_sdp_message_debugfs_write(struct file *f, const char __user *b
 	return write_size;
 }
 
-static ssize_t dp_dpcd_address_write(struct file *f, const char __user *buf,
-				 size_t size, loff_t *pos)
-{
-	int r;
-	struct amdgpu_dm_connector *connector = file_inode(f)->i_private;
-
-	if (size < sizeof(connector->debugfs_dpcd_address))
-		return -EINVAL;
-
-	r = copy_from_user(&connector->debugfs_dpcd_address,
-			buf, sizeof(connector->debugfs_dpcd_address));
-
-	return size - r;
-}
-
-static ssize_t dp_dpcd_size_write(struct file *f, const char __user *buf,
-				 size_t size, loff_t *pos)
-{
-	int r;
-	struct amdgpu_dm_connector *connector = file_inode(f)->i_private;
-
-	if (size < sizeof(connector->debugfs_dpcd_size))
-		return -EINVAL;
-
-	r = copy_from_user(&connector->debugfs_dpcd_size,
-			buf, sizeof(connector->debugfs_dpcd_size));
-
-	if (connector->debugfs_dpcd_size > 256)
-		connector->debugfs_dpcd_size = 0;
-
-	return size - r;
-}
-
-static ssize_t dp_dpcd_data_write(struct file *f, const char __user *buf,
-				 size_t size, loff_t *pos)
-{
-	int r;
-	char *data;
-	struct amdgpu_dm_connector *connector = file_inode(f)->i_private;
-	struct dc_link *link = connector->dc_link;
-	uint32_t write_size = connector->debugfs_dpcd_size;
-
-	if (!write_size || size < write_size)
-		return -EINVAL;
-
-	data = kzalloc(write_size, GFP_KERNEL);
-	if (!data)
-		return 0;
-
-	r = copy_from_user(data, buf, write_size);
-
-	dm_helpers_dp_write_dpcd(link->ctx, link,
-			connector->debugfs_dpcd_address, data, write_size - r);
-	kfree(data);
-	return write_size - r;
-}
-
-static ssize_t dp_dpcd_data_read(struct file *f, char __user *buf,
-				 size_t size, loff_t *pos)
-{
-	int r;
-	char *data;
-	struct amdgpu_dm_connector *connector = file_inode(f)->i_private;
-	struct dc_link *link = connector->dc_link;
-	uint32_t read_size = connector->debugfs_dpcd_size;
-
-	if (!read_size || size < read_size)
-		return 0;
-
-	data = kzalloc(read_size, GFP_KERNEL);
-	if (!data)
-		return 0;
-
-	dm_helpers_dp_read_dpcd(link->ctx, link,
-			connector->debugfs_dpcd_address, data, read_size);
-
-	r = copy_to_user(buf, data, read_size);
-
-	kfree(data);
-	return read_size - r;
-}
-
 /* function: Read link's DSC & FEC capabilities
  *
  *
@@ -2682,25 +2600,6 @@ static const struct file_operations sdp_message_fops = {
 	.llseek = default_llseek
 };
 
-static const struct file_operations dp_dpcd_address_debugfs_fops = {
-	.owner = THIS_MODULE,
-	.write = dp_dpcd_address_write,
-	.llseek = default_llseek
-};
-
-static const struct file_operations dp_dpcd_size_debugfs_fops = {
-	.owner = THIS_MODULE,
-	.write = dp_dpcd_size_write,
-	.llseek = default_llseek
-};
-
-static const struct file_operations dp_dpcd_data_debugfs_fops = {
-	.owner = THIS_MODULE,
-	.read = dp_dpcd_data_read,
-	.write = dp_dpcd_data_write,
-	.llseek = default_llseek
-};
-
 static const struct file_operations dp_max_bpc_debugfs_fops = {
 	.owner = THIS_MODULE,
 	.read = dp_max_bpc_read,
@@ -2724,9 +2623,6 @@ static const struct {
 		{"test_pattern", &dp_phy_test_pattern_fops},
 		{"hdcp_sink_capability", &hdcp_sink_capability_fops},
 		{"sdp_message", &sdp_message_fops},
-		{"aux_dpcd_address", &dp_dpcd_address_debugfs_fops},
-		{"aux_dpcd_size", &dp_dpcd_size_debugfs_fops},
-		{"aux_dpcd_data", &dp_dpcd_data_debugfs_fops},
 		{"dsc_clock_en", &dp_dsc_clock_en_debugfs_fops},
 		{"dsc_slice_width", &dp_dsc_slice_width_debugfs_fops},
 		{"dsc_slice_height", &dp_dsc_slice_height_debugfs_fops},
@@ -3025,9 +2921,6 @@ void connector_debugfs_init(struct amdgpu_dm_connector *connector)
 				    connector_debugfs_entries[i].fops);
 	}
 
-	connector->debugfs_dpcd_address = 0;
-	connector->debugfs_dpcd_size = 0;
-
 	if (connector->base.connector_type == DRM_MODE_CONNECTOR_HDMIA) {
 		for (i = 0; i < ARRAY_SIZE(hdmi_debugfs_entries); i++) {
 			debugfs_create_file(hdmi_debugfs_entries[i].name,