-Brian
> }
> EXPORT_SYMBOL(__drm_atomic_helper_connector_destroy_state);
>
> diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> index 9b9ba5d5ec0cb..d031e46ebffcf 100644
> --- a/drivers/gpu/drm/drm_connector.c
> +++ b/drivers/gpu/drm/drm_connector.c
> @@ -87,6 +87,7 @@ static struct drm_conn_prop_enum_list drm_connector_enum_list[] = {
> { DRM_MODE_CONNECTOR_VIRTUAL, "Virtual" },
> { DRM_MODE_CONNECTOR_DSI, "DSI" },
> { DRM_MODE_CONNECTOR_DPI, "DPI" },
> + { DRM_MODE_CONNECTOR_WRITEBACK, "Writeback" },
> };
>
> void drm_connector_ida_init(void)
> @@ -249,7 +250,8 @@ int drm_connector_init(struct drm_device *dev,
> config->num_connector++;
> spin_unlock_irq(&config->connector_list_lock);
>
> - if (connector_type != DRM_MODE_CONNECTOR_VIRTUAL)
> + if (connector_type != DRM_MODE_CONNECTOR_VIRTUAL &&
> + connector_type != DRM_MODE_CONNECTOR_WRITEBACK)
> drm_object_attach_property(&connector->base,
> config->edid_property,
> 0);
> diff --git a/drivers/gpu/drm/drm_writeback.c b/drivers/gpu/drm/drm_writeback.c
> new file mode 100644
> index 0000000000000..1141325b004ab
> --- /dev/null
> +++ b/drivers/gpu/drm/drm_writeback.c
> @@ -0,0 +1,255 @@
> +/*
> + * (C) COPYRIGHT 2016 ARM Limited. All rights reserved.
> + * Author: Brian Starkey <brian.starkey@xxxxxxx>
> + *
> + * This program is free software and is provided to you under the terms of the
> + * GNU General Public License version 2 as published by the Free Software
> + * Foundation, and any use by you of this program is subject to the terms
> + * of such GNU licence.
> + */
> +
> +#include <drm/drm_crtc.h>
> +#include <drm/drm_modeset_helper_vtables.h>
> +#include <drm/drm_property.h>
> +#include <drm/drm_writeback.h>
> +#include <drm/drmP.h>
> +
> +/**
> + * DOC: overview
> + *
> + * Writeback connectors are used to expose hardware which can write the output
> + * from a CRTC to a memory buffer. They are used and act similarly to other
> + * types of connectors, with some important differences:
> + * - Writeback connectors don't provide a way to output visually to the user.
> + * - Writeback connectors should always report as "disconnected" (so that
> + * clients which don't understand them will ignore them).
> + * - Writeback connectors don't have EDID.
> + *
> + * A framebuffer may only be attached to a writeback connector when the
> + * connector is attached to a CRTC. The WRITEBACK_FB_ID property which sets the
> + * framebuffer applies only to a single commit (see below). A framebuffer may
> + * not be attached while the CRTC is off.
> + *
> + * Writeback connectors have some additional properties, which userspace
> + * can use to query and control them:
> + *
> + * "WRITEBACK_FB_ID":
> + * Write-only object property storing a DRM_MODE_OBJECT_FB: it stores the
> + * framebuffer to be written by the writeback connector. This property is
> + * similar to the FB_ID property on planes, but will always read as zero
> + * and is not preserved across commits.
> + * Userspace must set this property to an output buffer every time it
> + * wishes the buffer to get filled.
> + *
> + * "WRITEBACK_PIXEL_FORMATS":
> + * Immutable blob property to store the supported pixel formats table. The
> + * data is an array of u32 DRM_FORMAT_* fourcc values.
> + * Userspace can use this blob to find out what pixel formats are supported
> + * by the connector's writeback engine.
> + */
> +
> +static int create_writeback_properties(struct drm_device *dev)
> +{
> + struct drm_property *prop;
> +
> + if (!dev->mode_config.writeback_fb_id_property) {
> + prop = drm_property_create_object(dev, DRM_MODE_PROP_ATOMIC,
> + "WRITEBACK_FB_ID",
> + DRM_MODE_OBJECT_FB);
> + if (!prop)
> + return -ENOMEM;
> + dev->mode_config.writeback_fb_id_property = prop;
> + }
> +
> + if (!dev->mode_config.writeback_pixel_formats_property) {
> + prop = drm_property_create(dev, DRM_MODE_PROP_BLOB |
> + DRM_MODE_PROP_ATOMIC |
> + DRM_MODE_PROP_IMMUTABLE,
> + "WRITEBACK_PIXEL_FORMATS", 0);
> + if (!prop)
> + return -ENOMEM;
> + dev->mode_config.writeback_pixel_formats_property = prop;
> + }
> +
> + return 0;
> +}
> +
> +static const struct drm_encoder_funcs drm_writeback_encoder_funcs = {
> + .destroy = drm_encoder_cleanup,
> +};
> +
> +/**
> + * drm_writeback_connector_init - Initialize a writeback connector and its properties
> + * @dev: DRM device
> + * @wb_connector: Writeback connector to initialize
> + * @con_funcs: Connector funcs vtable
> + * @enc_helper_funcs: Encoder helper funcs vtable to be used by the internal encoder
> + * @formats: Array of supported pixel formats for the writeback engine
> + * @n_formats: Length of the formats array
> + *
> + * This function creates the writeback-connector-specific properties if they
> + * have not been already created, initializes the connector as
> + * type DRM_MODE_CONNECTOR_WRITEBACK, and correctly initializes the property
> + * values. It will also create an internal encoder associated with the
> + * drm_writeback_connector and set it to use the @enc_helper_funcs vtable for
> + * the encoder helper.
> + *
> + * Drivers should always use this function instead of drm_connector_init() to
> + * set up writeback connectors.
> + *
> + * Returns: 0 on success, or a negative error code
> + */
> +int drm_writeback_connector_init(struct drm_device *dev,
> + struct drm_writeback_connector *wb_connector,
> + const struct drm_connector_funcs *con_funcs,
> + const struct drm_encoder_helper_funcs *enc_helper_funcs,
> + const u32 *formats, int n_formats)
> +{
> + struct drm_property_blob *blob;
> + struct drm_connector *connector = &wb_connector->base;
> + struct drm_mode_config *config = &dev->mode_config;
> + int ret = create_writeback_properties(dev);
> +
> + if (ret != 0)
> + return ret;
> +
> + blob = drm_property_create_blob(dev, n_formats * sizeof(*formats),
> + formats);
> + if (IS_ERR(blob))
> + return PTR_ERR(blob);
> +
> + drm_encoder_helper_add(&wb_connector->encoder, enc_helper_funcs);
> + ret = drm_encoder_init(dev, &wb_connector->encoder,
> + &drm_writeback_encoder_funcs,
> + DRM_MODE_ENCODER_VIRTUAL, NULL);
> + if (ret)
> + goto fail;
> +
> + connector->interlace_allowed = 0;
> +
> + ret = drm_connector_init(dev, connector, con_funcs,
> + DRM_MODE_CONNECTOR_WRITEBACK);
> + if (ret)
> + goto connector_fail;
> +
> + ret = drm_mode_connector_attach_encoder(connector,
> + &wb_connector->encoder);
> + if (ret)
> + goto attach_fail;
> +
> + INIT_LIST_HEAD(&wb_connector->job_queue);
> + spin_lock_init(&wb_connector->job_lock);
> +
> + drm_object_attach_property(&connector->base,
> + config->writeback_fb_id_property, 0);
> +
> + drm_object_attach_property(&connector->base,
> + config->writeback_pixel_formats_property,
> + blob->base.id);
> + wb_connector->pixel_formats_blob_ptr = blob;
> +
> + return 0;
> +
> +attach_fail:
> + drm_connector_cleanup(connector);
> +connector_fail:
> + drm_encoder_cleanup(&wb_connector->encoder);
> +fail:
> + drm_property_unreference_blob(blob);
> + return ret;
> +}
> +EXPORT_SYMBOL(drm_writeback_connector_init);
> +
> +/**
> + * drm_writeback_queue_job - Queue a writeback job for later signalling
> + * @wb_connector: The writeback connector to queue a job on
> + * @job: The job to queue
> + *
> + * This function adds a job to the job_queue for a writeback connector. It
> + * should be considered to take ownership of the writeback job, and so any other
> + * references to the job must be cleared after calling this function.
> + *
> + * Drivers must ensure that for a given writeback connector, jobs are queued in
> + * exactly the same order as they will be completed by the hardware (and
> + * signaled via drm_writeback_signal_completion).
> + *
> + * For every call to drm_writeback_queue_job() there must be exactly one call to
> + * drm_writeback_signal_completion()
> + *
> + * See also: drm_writeback_signal_completion()
> + */
> +void drm_writeback_queue_job(struct drm_writeback_connector *wb_connector,
> + struct drm_writeback_job *job)
> +{
> + unsigned long flags;
> +
> + spin_lock_irqsave(&wb_connector->job_lock, flags);
> + list_add_tail(&job->list_entry, &wb_connector->job_queue);
> + spin_unlock_irqrestore(&wb_connector->job_lock, flags);
> +}
> +EXPORT_SYMBOL(drm_writeback_queue_job);
> +
> +/**
> + * drm_writeback_cleanup_job - Cleanup and free a writeback job
> + * @job: The writeback job to free
> + *
> + * Drops any references held by the writeback job, and frees the structure.
> + */
> +void drm_writeback_cleanup_job(struct drm_writeback_job *job)
> +{
> + if (job->fb)
> + drm_framebuffer_unreference(job->fb);
> +}
> +EXPORT_SYMBOL(drm_writeback_cleanup_job);
> +
> +/*
> + * @cleanup_work: deferred cleanup of a writeback job
> + *
> + * The job cannot be cleaned up directly in drm_writeback_signal_completion,
> + * because it may be called in interrupt context. Dropping the framebuffer
> + * reference can sleep, and so the cleanup is deferred to a workqueue.
> + */
> +static void cleanup_work(struct work_struct *work)
> +{
> + struct drm_writeback_job *job = container_of(work,
> + struct drm_writeback_job,
> + cleanup_work);
> + drm_writeback_cleanup_job(job);
> +}
> +
> +/**
> + * drm_writeback_signal_completion - Signal the completion of a writeback job
> + * @wb_connector: The writeback connector whose job is complete
> + *
> + * Drivers should call this to signal the completion of a previously queued
> + * writeback job. It should be called as soon as possible after the hardware
> + * has finished writing, and may be called from interrupt context.
> + * It is the driver's responsibility to ensure that for a given connector, the
> + * hardware completes writeback jobs in the same order as they are queued.
> + *
> + * Unless the driver is holding its own reference to the framebuffer, it must
> + * not be accessed after calling this function.
> + *
> + * See also: drm_writeback_queue_job()
> + */
> +void
> +drm_writeback_signal_completion(struct drm_writeback_connector *wb_connector)
> +{
> + unsigned long flags;
> + struct drm_writeback_job *job;
> +
> + spin_lock_irqsave(&wb_connector->job_lock, flags);
> + job = list_first_entry_or_null(&wb_connector->job_queue,
> + struct drm_writeback_job,
> + list_entry);
> + if (job)
> + list_del(&job->list_entry);
> + spin_unlock_irqrestore(&wb_connector->job_lock, flags);
> +
> + if (WARN_ON(!job))
> + return;
> +
> + INIT_WORK(&job->cleanup_work, cleanup_work);
> + queue_work(system_long_wq, &job->cleanup_work);
> +}
> +EXPORT_SYMBOL(drm_writeback_signal_completion);
> diff --git a/include/drm/drm_atomic.h b/include/drm/drm_atomic.h
> index a57a8aa90ffb7..a5e904105db3a 100644
> --- a/include/drm/drm_atomic.h
> +++ b/include/drm/drm_atomic.h
> @@ -594,6 +594,9 @@ void drm_atomic_set_fence_for_plane(struct drm_plane_state *plane_state,
> int __must_check
> drm_atomic_set_crtc_for_connector(struct drm_connector_state *conn_state,
> struct drm_crtc *crtc);
> +int drm_atomic_set_writeback_fb_for_connector(
> + struct drm_connector_state *conn_state,
> + struct drm_framebuffer *fb);
> int __must_check
> drm_atomic_add_affected_connectors(struct drm_atomic_state *state,
> struct drm_crtc *crtc);
> diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> index 675cc3f8cf852..60c0ffb947d5e 100644
> --- a/include/drm/drm_connector.h
> +++ b/include/drm/drm_connector.h
> @@ -429,6 +429,19 @@ struct drm_connector_state {
> * protection. This is most commonly used for HDCP.
> */
> unsigned int content_protection;
> +
> + /**
> + * @writeback_job: Writeback job for writeback connectors
> + *
> + * Holds the framebuffer for a writeback connector. As the writeback
> + * completion may be asynchronous to the normal commit cycle, the
> + * writeback job lifetime is managed separately from the normal atomic
> + * state by this object.
> + *
> + * See also: drm_writeback_queue_job() and
> + * drm_writeback_signal_completion()
> + */
> + struct drm_writeback_job *writeback_job;
> };
>
> /**
> diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
> index 33b3a96d66d0a..9ca32bf7bf183 100644
> --- a/include/drm/drm_mode_config.h
> +++ b/include/drm/drm_mode_config.h
> @@ -779,6 +779,21 @@ struct drm_mode_config {
> */
> struct drm_property *panel_orientation_property;
>
> + /**
> + * @writeback_fb_id_property: Property for writeback connectors, storing
> + * the ID of the output framebuffer.
> + * See also: drm_writeback_connector_init()
> + */
> + struct drm_property *writeback_fb_id_property;
> +
> + /**
> + * @writeback_pixel_formats_property: Property for writeback connectors,
> + * storing an array of the supported pixel formats for the writeback
> + * engine (read-only).
> + * See also: drm_writeback_connector_init()
> + */
> + struct drm_property *writeback_pixel_formats_property;
> +
> /* dumb ioctl parameters */
> uint32_t preferred_depth, prefer_shadow;
>
> diff --git a/include/drm/drm_modeset_helper_vtables.h b/include/drm/drm_modeset_helper_vtables.h
> index 35e2a3a79fc56..3b289773297c2 100644
> --- a/include/drm/drm_modeset_helper_vtables.h
> +++ b/include/drm/drm_modeset_helper_vtables.h
> @@ -974,6 +974,17 @@ struct drm_connector_helper_funcs {
> */
> int (*atomic_check)(struct drm_connector *connector,
> struct drm_connector_state *state);
> +
> + /**
> + * @atomic_commit:
> + *
> + * This hook is to be used by drivers implementing writeback connectors
> + * that need a point when to commit the writeback job to the hardware.
> + *
> + * This callback is used by the atomic modeset helpers.
> + */
> + void (*atomic_commit)(struct drm_connector *connector,
> + struct drm_writeback_job *writeback_job);
> };
>
> /**
> diff --git a/include/drm/drm_writeback.h b/include/drm/drm_writeback.h
> new file mode 100644
> index 0000000000000..499c5c7b0a54e
> --- /dev/null
> +++ b/include/drm/drm_writeback.h
> @@ -0,0 +1,90 @@
> +/*
> + * (C) COPYRIGHT 2016 ARM Limited. All rights reserved.
> + * Author: Brian Starkey <brian.starkey@xxxxxxx>
> + *
> + * This program is free software and is provided to you under the terms of the
> + * GNU General Public License version 2 as published by the Free Software
> + * Foundation, and any use by you of this program is subject to the terms
> + * of such GNU licence.
> + */
> +
> +#ifndef __DRM_WRITEBACK_H__
> +#define __DRM_WRITEBACK_H__
> +#include <drm/drm_connector.h>
> +#include <drm/drm_encoder.h>
> +#include <linux/workqueue.h>
> +
> +struct drm_writeback_connector {
> + struct drm_connector base;
> +
> + /**
> + * @encoder: Internal encoder used by the connector to fulfill
> + * the DRM framework requirements. The users of the
> + * @drm_writeback_connector control the behaviour of the @encoder
> + * by passing the @enc_funcs parameter to drm_writeback_connector_init()
> + * function.
> + */
> + struct drm_encoder encoder;
> +
> + /**
> + * @pixel_formats_blob_ptr:
> + *
> + * DRM blob property data for the pixel formats list on writeback
> + * connectors
> + * See also drm_writeback_connector_init()
> + */
> + struct drm_property_blob *pixel_formats_blob_ptr;
> +
> + /** @job_lock: Protects job_queue */
> + spinlock_t job_lock;
> +
> + /**
> + * @job_queue:
> + *
> + * Holds a list of a connector's writeback jobs; the last item is the
> + * most recent. The first item may be either waiting for the hardware
> + * to begin writing, or currently being written.
> + *
> + * See also: drm_writeback_queue_job() and
> + * drm_writeback_signal_completion()
> + */
> + struct list_head job_queue;
> +};
> +
> +struct drm_writeback_job {
> + /**
> + * @cleanup_work:
> + *
> + * Used to allow drm_writeback_signal_completion to defer dropping the
> + * framebuffer reference to a workqueue.
> + */
> + struct work_struct cleanup_work;
> +
> + /**
> + * @list_entry:
> + *
> + * List item for the connector's @job_queue
> + */
> + struct list_head list_entry;
> +
> + /**
> + * @fb:
> + *
> + * Framebuffer to be written to by the writeback connector. Do not set
> + * directly, use drm_atomic_set_writeback_fb_for_connector()
> + */
> + struct drm_framebuffer *fb;
> +};
> +
> +int drm_writeback_connector_init(struct drm_device *dev,
> + struct drm_writeback_connector *wb_connector,
> + const struct drm_connector_funcs *con_funcs,
> + const struct drm_encoder_helper_funcs *enc_helper_funcs,
> + const u32 *formats, int n_formats);
> +
> +void drm_writeback_queue_job(struct drm_writeback_connector *wb_connector,
> + struct drm_writeback_job *job);
> +
> +void drm_writeback_cleanup_job(struct drm_writeback_job *job);
> +void drm_writeback_signal_completion(struct drm_writeback_connector *wb_connector);
> +#endif
> diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
> index 4b3a1bb58e680..3e6541f0400b8 100644
> --- a/include/uapi/drm/drm_mode.h
> +++ b/include/uapi/drm/drm_mode.h
> @@ -344,6 +344,7 @@ enum drm_mode_subconnector {
> #define DRM_MODE_CONNECTOR_VIRTUAL 15
> #define DRM_MODE_CONNECTOR_DSI 16
> #define DRM_MODE_CONNECTOR_DPI 17
> +#define DRM_MODE_CONNECTOR_WRITEBACK 18
>
> struct drm_mode_get_connector {
>
> --
> 2.17.0
>
