drm/msm/dpu: add the writeback connector layer

Introduce the dpu_writeback module which serves as the
interface between dpu operations and the drm_writeback.

This module manages the connector related operations for
dpu writeback.

changes in v2:
	- start using drm_writeback_connector_init_with_encoder()
	- drop unnecessary arguments from dpu_writeback_init()
	- rebase on msm-next tip and remove usage of priv->connectors

changes in v3:
	- none

changes in v4:
	- none

changes in v5:
	- store the drm_enc in the dpu_wb_conn to be used while
	  using dpu_encoder APIs

Signed-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/483520/
Link: https://lore.kernel.org/r/1650984096-9964-15-git-send-email-quic_abhinavk@quicinc.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

drivers/gpu/drm/msm/Makefile

@@ -80,6 +80,7 @@ msm-$(CONFIG_DRM_MSM_DPU) += \
 	disp/dpu1/dpu_plane.o \
 	disp/dpu1/dpu_rm.o \
 	disp/dpu1/dpu_vbif.o \
+	disp/dpu1/dpu_writeback.o
 
 msm-$(CONFIG_DRM_MSM_MDSS) += \
 	msm_mdss.o \

drivers/gpu/drm/msm/disp/dpu1/dpu_writeback.c

@@ -0,0 +1,76 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2022 Qualcomm Innovation Center, Inc. All rights reserved.
+ */
+
+#include "dpu_writeback.h"
+
+static int dpu_wb_conn_get_modes(struct drm_connector *connector)
+{
+	struct drm_device *dev = connector->dev;
+
+	return drm_add_modes_noedid(connector, dev->mode_config.max_width,
+			dev->mode_config.max_height);
+}
+
+static const struct drm_connector_funcs dpu_wb_conn_funcs = {
+	.reset = drm_atomic_helper_connector_reset,
+	.fill_modes = drm_helper_probe_single_connector_modes,
+	.destroy = drm_connector_cleanup,
+	.atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
+	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
+};
+
+static int dpu_wb_conn_prepare_job(struct drm_writeback_connector *connector,
+		struct drm_writeback_job *job)
+{
+
+	struct dpu_wb_connector *dpu_wb_conn = to_dpu_wb_conn(connector);
+
+	if (!job->fb)
+		return 0;
+
+	dpu_encoder_prepare_wb_job(dpu_wb_conn->wb_enc, job);
+
+	return 0;
+}
+
+static void dpu_wb_conn_cleanup_job(struct drm_writeback_connector *connector,
+		struct drm_writeback_job *job)
+{
+	struct dpu_wb_connector *dpu_wb_conn = to_dpu_wb_conn(connector);
+
+	if (!job->fb)
+		return;
+
+	dpu_encoder_cleanup_wb_job(dpu_wb_conn->wb_enc, job);
+}
+
+static const struct drm_connector_helper_funcs dpu_wb_conn_helper_funcs = {
+	.get_modes = dpu_wb_conn_get_modes,
+	.prepare_writeback_job = dpu_wb_conn_prepare_job,
+	.cleanup_writeback_job = dpu_wb_conn_cleanup_job,
+};
+
+int dpu_writeback_init(struct drm_device *dev, struct drm_encoder *enc,
+		const u32 *format_list, u32 num_formats)
+{
+	struct dpu_wb_connector *dpu_wb_conn;
+	int rc = 0;
+
+	dpu_wb_conn = devm_kzalloc(dev->dev, sizeof(*dpu_wb_conn), GFP_KERNEL);
+
+	drm_connector_helper_add(&dpu_wb_conn->base.base, &dpu_wb_conn_helper_funcs);
+
+	/* DPU initializes the encoder and sets it up completely for writeback
+	 * cases and hence should use the new API drm_writeback_connector_init_with_encoder
+	 * to initialize the writeback connector
+	 */
+	rc = drm_writeback_connector_init_with_encoder(dev, &dpu_wb_conn->base, enc,
+			&dpu_wb_conn_funcs, format_list, num_formats);
+
+	if (!rc)
+		dpu_wb_conn->wb_enc = enc;
+
+	return rc;
+}

drivers/gpu/drm/msm/disp/dpu1/dpu_writeback.h

@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) 2022 Qualcomm Innovation Center, Inc. All rights reserved.
+ */
+
+#ifndef _DPU_WRITEBACK_H
+#define _DPU_WRITEBACK_H
+
+#include <drm/drm_crtc.h>
+#include <drm/drm_file.h>
+#include <drm/drm_probe_helper.h>
+#include <drm/drm_writeback.h>
+
+#include "msm_drv.h"
+#include "dpu_kms.h"
+#include "dpu_encoder_phys.h"
+
+struct dpu_wb_connector {
+	struct drm_writeback_connector base;
+	struct drm_encoder *wb_enc;
+};
+
+static inline struct dpu_wb_connector *to_dpu_wb_conn(struct drm_writeback_connector *conn)
+{
+	return container_of(conn, struct dpu_wb_connector, base);
+}
+
+int dpu_writeback_init(struct drm_device *dev, struct drm_encoder *enc,
+		const u32 *format_list, u32 num_formats);
+
+#endif /*_DPU_WRITEBACK_H */