[PATCH V2 5/5] drm/vkms: Add support for writeback

[Rodrigo Siqueira]

This patch implements the necessary functions to add writeback support
for vkms. This feature is useful for testing compositors if you don't
have hardware with writeback support.

Change in V2:
- Rework signal completion (Brian)
- Integrates writeback with active_planes (Daniel)
- Compose cursor (Daniel)

Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo@xxxxxxxxx>
---
 drivers/gpu/drm/vkms/Makefile         |   3 +-
 drivers/gpu/drm/vkms/vkms_drv.c       |   7 ++
 drivers/gpu/drm/vkms/vkms_drv.h       |   6 +
 drivers/gpu/drm/vkms/vkms_output.c    |   6 +
 drivers/gpu/drm/vkms/vkms_writeback.c | 166 ++++++++++++++++++++++++++
 5 files changed, 187 insertions(+), 1 deletion(-)
 create mode 100644 drivers/gpu/drm/vkms/vkms_writeback.c

diff --git a/drivers/gpu/drm/vkms/Makefile b/drivers/gpu/drm/vkms/Makefile
index b4c040854bd6..091e6fa643d1 100644
--- a/drivers/gpu/drm/vkms/Makefile
+++ b/drivers/gpu/drm/vkms/Makefile
@@ -6,6 +6,7 @@ vkms-y := \
 	vkms_crtc.o \
 	vkms_gem.o \
 	vkms_composer.o \
-	vkms_crc.o
+	vkms_crc.o \
+	vkms_writeback.o
 
 obj-$(CONFIG_DRM_VKMS) += vkms.o
diff --git a/drivers/gpu/drm/vkms/vkms_drv.c b/drivers/gpu/drm/vkms/vkms_drv.c
index 966b3d653189..d870779abf9d 100644
--- a/drivers/gpu/drm/vkms/vkms_drv.c
+++ b/drivers/gpu/drm/vkms/vkms_drv.c
@@ -30,6 +30,10 @@ bool enable_cursor;
 module_param_named(enable_cursor, enable_cursor, bool, 0444);
 MODULE_PARM_DESC(enable_cursor, "Enable/Disable cursor support");
 
+bool enable_writeback;
+module_param_named(enable_writeback, enable_writeback, bool, 0444);
+MODULE_PARM_DESC(enable_writeback, "Enable/Disable writeback connector");
+
 static const struct file_operations vkms_driver_fops = {
 	.owner		= THIS_MODULE,
 	.open		= drm_open,
@@ -158,6 +162,9 @@ static int __init vkms_init(void)
 		goto out_fini;
 	}
 
+	if (enable_writeback)
+		DRM_INFO("Writeback connector enabled");
+
 	ret = vkms_modeset_init(vkms_device);
 	if (ret)
 		goto out_fini;
diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
index ad63dbe5e994..bf3fa737b3d7 100644
--- a/drivers/gpu/drm/vkms/vkms_drv.h
+++ b/drivers/gpu/drm/vkms/vkms_drv.h
@@ -7,6 +7,7 @@
 #include <drm/drm.h>
 #include <drm/drm_gem.h>
 #include <drm/drm_encoder.h>
+#include <drm/drm_writeback.h>
 #include <linux/hrtimer.h>
 
 #define XRES_MIN    20
@@ -19,6 +20,7 @@
 #define YRES_MAX  8192
 
 extern bool enable_cursor;
+extern bool enable_writeback;
 
 struct vkms_data {
 	struct drm_framebuffer fb;
@@ -63,6 +65,7 @@ struct vkms_output {
 	struct drm_crtc crtc;
 	struct drm_encoder encoder;
 	struct drm_connector connector;
+	struct drm_writeback_connector wb_connector;
 	struct hrtimer vblank_hrtimer;
 	ktime_t period_ns;
 	struct drm_pending_vblank_event *event;
@@ -143,4 +146,7 @@ int vkms_verify_crc_source(struct drm_crtc *crtc, const char *source_name,
 			   size_t *values_cnt);
 void vkms_crc_work_handle(struct work_struct *work);
 
+/* Writeback */
+int enable_writeback_connector(struct vkms_device *vkmsdev);
+
 #endif /* _VKMS_DRV_H_ */
diff --git a/drivers/gpu/drm/vkms/vkms_output.c b/drivers/gpu/drm/vkms/vkms_output.c
index fb1941a6522c..3b093ae8f373 100644
--- a/drivers/gpu/drm/vkms/vkms_output.c
+++ b/drivers/gpu/drm/vkms/vkms_output.c
@@ -84,6 +84,12 @@ int vkms_output_init(struct vkms_device *vkmsdev, int index)
 		goto err_attach;
 	}
 
+	if (enable_writeback) {
+		ret = enable_writeback_connector(vkmsdev);
+		if (ret)
+			DRM_ERROR("Failed to init writeback connector\n");
+	}
+
 	drm_mode_config_reset(dev);
 
 	return 0;
diff --git a/drivers/gpu/drm/vkms/vkms_writeback.c b/drivers/gpu/drm/vkms/vkms_writeback.c
new file mode 100644
index 000000000000..56632eb393cb
--- /dev/null
+++ b/drivers/gpu/drm/vkms/vkms_writeback.c
@@ -0,0 +1,166 @@
+// SPDX-License-Identifier: GPL-2.0+
+
+#include "vkms_drv.h"
+#include "vkms_composer.h"
+#include <drm/drm_writeback.h>
+#include <drm/drm_probe_helper.h>
+#include <drm/drm_atomic_helper.h>
+#include <drm/drm_gem_framebuffer_helper.h>
+
+static const u32 vkms_wb_formats[] = {
+	DRM_FORMAT_XRGB8888,
+};
+
+static const struct drm_connector_funcs vkms_wb_connector_funcs = {
+	.fill_modes = drm_helper_probe_single_connector_modes,
+	.destroy = drm_connector_cleanup,
+	.reset = drm_atomic_helper_connector_reset,
+	.atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
+	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
+};
+
+static int vkms_wb_encoder_atomic_check(struct drm_encoder *encoder,
+					struct drm_crtc_state *crtc_state,
+					struct drm_connector_state *conn_state)
+{
+	struct drm_framebuffer *fb;
+	const struct drm_display_mode *mode = &crtc_state->mode;
+
+	if (!conn_state->writeback_job || !conn_state->writeback_job->fb)
+		return 0;
+
+	fb = conn_state->writeback_job->fb;
+	if (fb->width != mode->hdisplay || fb->height != mode->vdisplay) {
+		DRM_DEBUG_KMS("Invalid framebuffer size %ux%u\n",
+			      fb->width, fb->height);
+		return -EINVAL;
+	}
+
+	if (fb->format->format != DRM_FORMAT_XRGB8888) {
+		struct drm_format_name_buf format_name;
+
+		DRM_DEBUG_KMS("Invalid pixel format %s\n",
+			      drm_get_format_name(fb->format->format,
+						  &format_name));
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static const struct drm_encoder_helper_funcs vkms_wb_encoder_helper_funcs = {
+	.atomic_check = vkms_wb_encoder_atomic_check,
+};
+
+static int vkms_wb_connector_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 int vkms_wb_prepare_job(struct drm_writeback_connector *wb_connector,
+			       struct drm_writeback_job *job)
+{
+	struct vkms_gem_object *vkms_obj;
+	struct drm_gem_object *gem_obj;
+	int ret;
+
+	if (!job->fb)
+		return 0;
+
+	gem_obj = drm_gem_fb_get_obj(job->fb, 0);
+	ret = vkms_gem_vmap(gem_obj);
+	if (ret) {
+		DRM_ERROR("vmap failed: %d\n", ret);
+		return ret;
+	}
+
+	vkms_obj = drm_gem_to_vkms_gem(gem_obj);
+	job->priv = vkms_obj->vaddr;
+
+	return 0;
+}
+
+static void vkms_wb_cleanup_job(struct drm_writeback_connector *connector,
+				struct drm_writeback_job *job)
+{
+	struct drm_gem_object *gem_obj;
+
+	if (!job->fb)
+		return;
+
+	gem_obj = drm_gem_fb_get_obj(job->fb, 0);
+	vkms_gem_vunmap(gem_obj);
+}
+
+static void vkms_wb_atomic_commit(struct drm_connector *conn,
+				  struct drm_connector_state *state)
+{
+	struct vkms_device *vkmsdev = drm_device_to_vkms_device(conn->dev);
+	struct vkms_output *output = &vkmsdev->output;
+	struct vkms_crtc_state *crtc_state = output->crc_state;
+	struct drm_writeback_connector *wb_conn = &output->wb_connector;
+	struct drm_connector_state *conn_state = wb_conn->base.state;
+	void *priv_data = conn_state->writeback_job->priv;
+	struct vkms_data *primary_data = NULL;
+	struct vkms_data *cursor_data = NULL;
+	struct drm_framebuffer *fb = NULL;
+	struct vkms_gem_object *vkms_obj;
+	struct drm_gem_object *gem_obj;
+
+	if (!conn_state)
+		return;
+
+	if (!conn_state->writeback_job || !conn_state->writeback_job->fb) {
+		DRM_DEBUG_DRIVER("Disable writeback\n");
+		return;
+	}
+
+	if (crtc_state->num_active_planes >= 1)
+		primary_data = crtc_state->active_planes[0]->data;
+
+	if (crtc_state->num_active_planes == 2)
+		cursor_data = crtc_state->active_planes[1]->data;
+
+	if (!primary_data)
+		return;
+
+	fb = &primary_data->fb;
+	gem_obj = drm_gem_fb_get_obj(fb, 0);
+	vkms_obj = drm_gem_to_vkms_gem(gem_obj);
+
+	if (!vkms_obj->vaddr || !priv_data)
+		return;
+
+	drm_writeback_queue_job(wb_conn, state);
+
+	memcpy(priv_data, vkms_obj->vaddr, vkms_obj->gem.size);
+	if (cursor_data)
+		compose_cursor(cursor_data, primary_data, priv_data);
+
+	drm_writeback_signal_completion(wb_conn, 0);
+}
+
+static const struct drm_connector_helper_funcs vkms_wb_conn_helper_funcs = {
+	.get_modes = vkms_wb_connector_get_modes,
+	.prepare_writeback_job = vkms_wb_prepare_job,
+	.cleanup_writeback_job = vkms_wb_cleanup_job,
+	.atomic_commit = vkms_wb_atomic_commit,
+};
+
+int enable_writeback_connector(struct vkms_device *vkmsdev)
+{
+	struct drm_writeback_connector *wb = &vkmsdev->output.wb_connector;
+
+	vkmsdev->output.wb_connector.encoder.possible_crtcs = 1;
+	drm_connector_helper_add(&wb->base, &vkms_wb_conn_helper_funcs);
+
+	return drm_writeback_connector_init(&vkmsdev->drm, wb,
+					    &vkms_wb_connector_funcs,
+					    &vkms_wb_encoder_helper_funcs,
+					    vkms_wb_formats,
+					    ARRAY_SIZE(vkms_wb_formats));
+}
+
-- 
2.21.0