[PATCH 2/2] 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 donât
have hardware with writeback support.

Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo@xxxxxxxxx>
---
 drivers/gpu/drm/vkms/Makefile         |   9 +-
 drivers/gpu/drm/vkms/vkms_crtc.c      |   5 +
 drivers/gpu/drm/vkms/vkms_drv.c       |  10 ++
 drivers/gpu/drm/vkms/vkms_drv.h       |  12 ++
 drivers/gpu/drm/vkms/vkms_output.c    |   6 +
 drivers/gpu/drm/vkms/vkms_writeback.c | 165 ++++++++++++++++++++++++++
 6 files changed, 206 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 89f09bec7b23..90eb7acd618d 100644
--- a/drivers/gpu/drm/vkms/Makefile
+++ b/drivers/gpu/drm/vkms/Makefile
@@ -1,4 +1,11 @@
 # SPDX-License-Identifier: GPL-2.0-only
-vkms-y := vkms_drv.o vkms_plane.o vkms_output.o vkms_crtc.o vkms_gem.o vkms_crc.o
+vkms-y := \
+	vkms_drv.o \
+	vkms_plane.o \
+	vkms_output.o \
+	vkms_crtc.o \
+	vkms_gem.o \
+	vkms_crc.o \
+	vkms_writeback.o
 
 obj-$(CONFIG_DRM_VKMS) += vkms.o
diff --git a/drivers/gpu/drm/vkms/vkms_crtc.c b/drivers/gpu/drm/vkms/vkms_crtc.c
index 1bbe099b7db8..ce797e265b1b 100644
--- a/drivers/gpu/drm/vkms/vkms_crtc.c
+++ b/drivers/gpu/drm/vkms/vkms_crtc.c
@@ -23,6 +23,11 @@ static enum hrtimer_restart vkms_vblank_simulate(struct hrtimer *timer)
 	if (!ret)
 		DRM_ERROR("vkms failure on handling vblank");
 
+	if (output->writeback_status == WB_START) {
+		drm_writeback_signal_completion(&output->wb_connector, 0);
+		output->writeback_status = WB_STOP;
+	}
+
 	if (state && output->crc_enabled) {
 		u64 frame = drm_crtc_accurate_vblank_count(crtc);
 
diff --git a/drivers/gpu/drm/vkms/vkms_drv.c b/drivers/gpu/drm/vkms/vkms_drv.c
index 92296bd8f623..d5917d5a45e3 100644
--- a/drivers/gpu/drm/vkms/vkms_drv.c
+++ b/drivers/gpu/drm/vkms/vkms_drv.c
@@ -29,6 +29,10 @@ bool enable_cursor;
 module_param_named(enable_cursor, enable_cursor, bool, 0444);
 MODULE_PARM_DESC(enable_cursor, "Enable/Disable cursor support");
 
+int enable_writeback;
+module_param_named(enable_writeback, enable_writeback, int, 0444);
+MODULE_PARM_DESC(enable_writeback, "Enable/Disable writeback connector");
+
 static const struct file_operations vkms_driver_fops = {
 	.owner		= THIS_MODULE,
 	.open		= drm_open,
@@ -123,6 +127,12 @@ static int __init vkms_init(void)
 		goto out_fini;
 	}
 
+	vkms_device->output.writeback_status = WB_DISABLED;
+	if (enable_writeback) {
+		vkms_device->output.writeback_status = WB_STOP;
+		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 e81073dea154..ca1f9ee63ec8 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
@@ -60,14 +61,22 @@ struct vkms_crtc_state {
 	u64 frame_end;
 };
 
+enum wb_status {
+	WB_DISABLED,
+	WB_START,
+	WB_STOP,
+};
+
 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;
 	bool crc_enabled;
+	enum wb_status writeback_status;
 	/* ordered wq for crc_work */
 	struct workqueue_struct *crc_workq;
 	/* protects concurrent access to crc_data */
@@ -141,4 +150,7 @@ 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 1442b447c707..1fc1d4e9585c 100644
--- a/drivers/gpu/drm/vkms/vkms_output.c
+++ b/drivers/gpu/drm/vkms/vkms_output.c
@@ -91,6 +91,12 @@ int vkms_output_init(struct vkms_device *vkmsdev, int index)
 		goto err_attach;
 	}
 
+	if (vkmsdev->output.writeback_status != WB_DISABLED) {
+		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..f7b962ae5646
--- /dev/null
+++ b/drivers/gpu/drm/vkms/vkms_writeback.c
@@ -0,0 +1,165 @@
+// SPDX-License-Identifier: GPL-2.0+
+
+#include "vkms_drv.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 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 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_crc_data *primary_data = NULL;
+	struct drm_framebuffer *fb = NULL;
+	struct vkms_gem_object *vkms_obj;
+	struct drm_gem_object *gem_obj;
+	struct drm_plane *plane;
+
+	if (!conn_state)
+		return;
+
+	if (!conn_state->writeback_job || !conn_state->writeback_job->fb) {
+		output->writeback_status = WB_STOP;
+		DRM_DEBUG_DRIVER("Disable writeback\n");
+		return;
+	}
+
+	drm_for_each_plane(plane, &vkmsdev->drm) {
+		struct vkms_plane_state *vplane_state;
+		struct vkms_crc_data *plane_data;
+
+		vplane_state = to_vkms_plane_state(plane->state);
+		plane_data = vplane_state->crc_data;
+
+		if (drm_framebuffer_read_refcount(&plane_data->fb) == 0)
+			continue;
+
+		if (plane->type == DRM_PLANE_TYPE_PRIMARY)
+			primary_data = plane_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;
+
+	memcpy(priv_data, vkms_obj->vaddr, vkms_obj->gem.size);
+	drm_writeback_queue_job(wb_conn, state);
+	output->writeback_status = WB_START;
+}
+
+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_formats,
+					    ARRAY_SIZE(vkms_formats));
+}
+
-- 
2.21.0

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