Re: [PATCH 9/9] drm/xen-front: Implement communication with backend

[Daniel Vetter]

On Wed, Feb 21, 2018 at 10:03:42AM +0200, Oleksandr Andrushchenko wrote:
> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
> 
> Handle communication with the backend:
>  - send requests and wait for the responses according
>    to the displif protocol
>  - serialize access to the communication channel
>  - time-out used for backend communication is set to 3000 ms
>  - manage display buffers shared with the backend
> 
> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>

After the demidlayering it probably makes sense to merge this with the
overall kms/basic-drm-driver patch. Up to you really.
-Daniel
> ---
>  drivers/gpu/drm/xen/xen_drm_front.c | 327 +++++++++++++++++++++++++++++++++++-
>  drivers/gpu/drm/xen/xen_drm_front.h |   5 +
>  2 files changed, 327 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xen/xen_drm_front.c b/drivers/gpu/drm/xen/xen_drm_front.c
> index 8de88e359d5e..5ad546231d30 100644
> --- a/drivers/gpu/drm/xen/xen_drm_front.c
> +++ b/drivers/gpu/drm/xen/xen_drm_front.c
> @@ -31,12 +31,146 @@
>  #include "xen_drm_front_evtchnl.h"
>  #include "xen_drm_front_shbuf.h"
>  
> +/* timeout in ms to wait for backend to respond */
> +#define VDRM_WAIT_BACK_MS	3000
> +
> +struct xen_drm_front_dbuf {
> +	struct list_head list;
> +	uint64_t dbuf_cookie;
> +	uint64_t fb_cookie;
> +	struct xen_drm_front_shbuf *shbuf;
> +};
> +
> +static int dbuf_add_to_list(struct xen_drm_front_info *front_info,
> +		struct xen_drm_front_shbuf *shbuf, uint64_t dbuf_cookie)
> +{
> +	struct xen_drm_front_dbuf *dbuf;
> +
> +	dbuf = kzalloc(sizeof(*dbuf), GFP_KERNEL);
> +	if (!dbuf)
> +		return -ENOMEM;
> +
> +	dbuf->dbuf_cookie = dbuf_cookie;
> +	dbuf->shbuf = shbuf;
> +	list_add(&dbuf->list, &front_info->dbuf_list);
> +	return 0;
> +}
> +
> +static struct xen_drm_front_dbuf *dbuf_get(struct list_head *dbuf_list,
> +		uint64_t dbuf_cookie)
> +{
> +	struct xen_drm_front_dbuf *buf, *q;
> +
> +	list_for_each_entry_safe(buf, q, dbuf_list, list)
> +		if (buf->dbuf_cookie == dbuf_cookie)
> +			return buf;
> +
> +	return NULL;
> +}
> +
> +static void dbuf_flush_fb(struct list_head *dbuf_list, uint64_t fb_cookie)
> +{
> +	struct xen_drm_front_dbuf *buf, *q;
> +
> +	list_for_each_entry_safe(buf, q, dbuf_list, list)
> +		if (buf->fb_cookie == fb_cookie)
> +			xen_drm_front_shbuf_flush(buf->shbuf);
> +}
> +
> +static void dbuf_free(struct list_head *dbuf_list, uint64_t dbuf_cookie)
> +{
> +	struct xen_drm_front_dbuf *buf, *q;
> +
> +	list_for_each_entry_safe(buf, q, dbuf_list, list)
> +		if (buf->dbuf_cookie == dbuf_cookie) {
> +			list_del(&buf->list);
> +			xen_drm_front_shbuf_unmap(buf->shbuf);
> +			xen_drm_front_shbuf_free(buf->shbuf);
> +			kfree(buf);
> +			break;
> +		}
> +}
> +
> +static void dbuf_free_all(struct list_head *dbuf_list)
> +{
> +	struct xen_drm_front_dbuf *buf, *q;
> +
> +	list_for_each_entry_safe(buf, q, dbuf_list, list) {
> +		list_del(&buf->list);
> +		xen_drm_front_shbuf_unmap(buf->shbuf);
> +		xen_drm_front_shbuf_free(buf->shbuf);
> +		kfree(buf);
> +	}
> +}
> +
> +static struct xendispl_req *be_prepare_req(
> +		struct xen_drm_front_evtchnl *evtchnl, uint8_t operation)
> +{
> +	struct xendispl_req *req;
> +
> +	req = RING_GET_REQUEST(&evtchnl->u.req.ring,
> +			evtchnl->u.req.ring.req_prod_pvt);
> +	req->operation = operation;
> +	req->id = evtchnl->evt_next_id++;
> +	evtchnl->evt_id = req->id;
> +	return req;
> +}
> +
> +static int be_stream_do_io(struct xen_drm_front_evtchnl *evtchnl,
> +		struct xendispl_req *req)
> +{
> +	reinit_completion(&evtchnl->u.req.completion);
> +	if (unlikely(evtchnl->state != EVTCHNL_STATE_CONNECTED))
> +		return -EIO;
> +
> +	xen_drm_front_evtchnl_flush(evtchnl);
> +	return 0;
> +}
> +
> +static int be_stream_wait_io(struct xen_drm_front_evtchnl *evtchnl)
> +{
> +	if (wait_for_completion_timeout(&evtchnl->u.req.completion,
> +			msecs_to_jiffies(VDRM_WAIT_BACK_MS)) <= 0)
> +		return -ETIMEDOUT;
> +
> +	return evtchnl->u.req.resp_status;
> +}
> +
>  static int be_mode_set(struct xen_drm_front_drm_pipeline *pipeline, uint32_t x,
>  		uint32_t y, uint32_t width, uint32_t height, uint32_t bpp,
>  		uint64_t fb_cookie)
>  
>  {
> -	return 0;
> +	struct xen_drm_front_evtchnl *evtchnl;
> +	struct xen_drm_front_info *front_info;
> +	struct xendispl_req *req;
> +	unsigned long flags;
> +	int ret;
> +
> +	front_info = pipeline->drm_info->front_info;
> +	evtchnl = &front_info->evt_pairs[pipeline->index].req;
> +	if (unlikely(!evtchnl))
> +		return -EIO;
> +
> +	mutex_lock(&front_info->req_io_lock);
> +
> +	spin_lock_irqsave(&front_info->io_lock, flags);
> +	req = be_prepare_req(evtchnl, XENDISPL_OP_SET_CONFIG);
> +	req->op.set_config.x = x;
> +	req->op.set_config.y = y;
> +	req->op.set_config.width = width;
> +	req->op.set_config.height = height;
> +	req->op.set_config.bpp = bpp;
> +	req->op.set_config.fb_cookie = fb_cookie;
> +
> +	ret = be_stream_do_io(evtchnl, req);
> +	spin_unlock_irqrestore(&front_info->io_lock, flags);
> +
> +	if (ret == 0)
> +		ret = be_stream_wait_io(evtchnl);
> +
> +	mutex_unlock(&front_info->req_io_lock);
> +	return ret;
>  }
>  
>  static int be_dbuf_create_int(struct xen_drm_front_info *front_info,
> @@ -44,7 +178,69 @@ static int be_dbuf_create_int(struct xen_drm_front_info *front_info,
>  		uint32_t bpp, uint64_t size, struct page **pages,
>  		struct sg_table *sgt)
>  {
> +	struct xen_drm_front_evtchnl *evtchnl;
> +	struct xen_drm_front_shbuf *shbuf;
> +	struct xendispl_req *req;
> +	struct xen_drm_front_shbuf_cfg buf_cfg;
> +	unsigned long flags;
> +	int ret;
> +
> +	evtchnl = &front_info->evt_pairs[GENERIC_OP_EVT_CHNL].req;
> +	if (unlikely(!evtchnl))
> +		return -EIO;
> +
> +	memset(&buf_cfg, 0, sizeof(buf_cfg));
> +	buf_cfg.xb_dev = front_info->xb_dev;
> +	buf_cfg.pages = pages;
> +	buf_cfg.size = size;
> +	buf_cfg.sgt = sgt;
> +	buf_cfg.be_alloc = front_info->cfg.be_alloc;
> +
> +	shbuf = xen_drm_front_shbuf_alloc(&buf_cfg);
> +	if (!shbuf)
> +		return -ENOMEM;
> +
> +	ret = dbuf_add_to_list(front_info, shbuf, dbuf_cookie);
> +	if (ret < 0) {
> +		xen_drm_front_shbuf_free(shbuf);
> +		return ret;
> +	}
> +
> +	mutex_lock(&front_info->req_io_lock);
> +
> +	spin_lock_irqsave(&front_info->io_lock, flags);
> +	req = be_prepare_req(evtchnl, XENDISPL_OP_DBUF_CREATE);
> +	req->op.dbuf_create.gref_directory =
> +			xen_drm_front_shbuf_get_dir_start(shbuf);
> +	req->op.dbuf_create.buffer_sz = size;
> +	req->op.dbuf_create.dbuf_cookie = dbuf_cookie;
> +	req->op.dbuf_create.width = width;
> +	req->op.dbuf_create.height = height;
> +	req->op.dbuf_create.bpp = bpp;
> +	if (buf_cfg.be_alloc)
> +		req->op.dbuf_create.flags |= XENDISPL_DBUF_FLG_REQ_ALLOC;
> +
> +	ret = be_stream_do_io(evtchnl, req);
> +	spin_unlock_irqrestore(&front_info->io_lock, flags);
> +
> +	if (ret < 0)
> +		goto fail;
> +
> +	ret = be_stream_wait_io(evtchnl);
> +	if (ret < 0)
> +		goto fail;
> +
> +	ret = xen_drm_front_shbuf_map(shbuf);
> +	if (ret < 0)
> +		goto fail;
> +
> +	mutex_unlock(&front_info->req_io_lock);
>  	return 0;
> +
> +fail:
> +	mutex_unlock(&front_info->req_io_lock);
> +	dbuf_free(&front_info->dbuf_list, dbuf_cookie);
> +	return ret;
>  }
>  
>  static int be_dbuf_create_from_sgt(struct xen_drm_front_info *front_info,
> @@ -66,26 +262,144 @@ static int be_dbuf_create_from_pages(struct xen_drm_front_info *front_info,
>  static int be_dbuf_destroy(struct xen_drm_front_info *front_info,
>  		uint64_t dbuf_cookie)
>  {
> -	return 0;
> +	struct xen_drm_front_evtchnl *evtchnl;
> +	struct xendispl_req *req;
> +	unsigned long flags;
> +	bool be_alloc;
> +	int ret;
> +
> +	evtchnl = &front_info->evt_pairs[GENERIC_OP_EVT_CHNL].req;
> +	if (unlikely(!evtchnl))
> +		return -EIO;
> +
> +	be_alloc = front_info->cfg.be_alloc;
> +
> +	/*
> +	 * for the backend allocated buffer release references now, so backend
> +	 * can free the buffer
> +	 */
> +	if (be_alloc)
> +		dbuf_free(&front_info->dbuf_list, dbuf_cookie);
> +
> +	mutex_lock(&front_info->req_io_lock);
> +
> +	spin_lock_irqsave(&front_info->io_lock, flags);
> +	req = be_prepare_req(evtchnl, XENDISPL_OP_DBUF_DESTROY);
> +	req->op.dbuf_destroy.dbuf_cookie = dbuf_cookie;
> +
> +	ret = be_stream_do_io(evtchnl, req);
> +	spin_unlock_irqrestore(&front_info->io_lock, flags);
> +
> +	if (ret == 0)
> +		ret = be_stream_wait_io(evtchnl);
> +
> +	/*
> +	 * do this regardless of communication status with the backend:
> +	 * if we cannot remove remote resources remove what we can locally
> +	 */
> +	if (!be_alloc)
> +		dbuf_free(&front_info->dbuf_list, dbuf_cookie);
> +
> +	mutex_unlock(&front_info->req_io_lock);
> +	return ret;
>  }
>  
>  static int be_fb_attach(struct xen_drm_front_info *front_info,
>  		uint64_t dbuf_cookie, uint64_t fb_cookie, uint32_t width,
>  		uint32_t height, uint32_t pixel_format)
>  {
> -	return 0;
> +	struct xen_drm_front_evtchnl *evtchnl;
> +	struct xen_drm_front_dbuf *buf;
> +	struct xendispl_req *req;
> +	unsigned long flags;
> +	int ret;
> +
> +	evtchnl = &front_info->evt_pairs[GENERIC_OP_EVT_CHNL].req;
> +	if (unlikely(!evtchnl))
> +		return -EIO;
> +
> +	buf = dbuf_get(&front_info->dbuf_list, dbuf_cookie);
> +	if (!buf)
> +		return -EINVAL;
> +
> +	buf->fb_cookie = fb_cookie;
> +
> +	mutex_lock(&front_info->req_io_lock);
> +
> +	spin_lock_irqsave(&front_info->io_lock, flags);
> +	req = be_prepare_req(evtchnl, XENDISPL_OP_FB_ATTACH);
> +	req->op.fb_attach.dbuf_cookie = dbuf_cookie;
> +	req->op.fb_attach.fb_cookie = fb_cookie;
> +	req->op.fb_attach.width = width;
> +	req->op.fb_attach.height = height;
> +	req->op.fb_attach.pixel_format = pixel_format;
> +
> +	ret = be_stream_do_io(evtchnl, req);
> +	spin_unlock_irqrestore(&front_info->io_lock, flags);
> +
> +	if (ret == 0)
> +		ret = be_stream_wait_io(evtchnl);
> +
> +	mutex_unlock(&front_info->req_io_lock);
> +	return ret;
>  }
>  
>  static int be_fb_detach(struct xen_drm_front_info *front_info,
>  		uint64_t fb_cookie)
>  {
> -	return 0;
> +	struct xen_drm_front_evtchnl *evtchnl;
> +	struct xendispl_req *req;
> +	unsigned long flags;
> +	int ret;
> +
> +	evtchnl = &front_info->evt_pairs[GENERIC_OP_EVT_CHNL].req;
> +	if (unlikely(!evtchnl))
> +		return -EIO;
> +
> +	mutex_lock(&front_info->req_io_lock);
> +
> +	spin_lock_irqsave(&front_info->io_lock, flags);
> +	req = be_prepare_req(evtchnl, XENDISPL_OP_FB_DETACH);
> +	req->op.fb_detach.fb_cookie = fb_cookie;
> +
> +	ret = be_stream_do_io(evtchnl, req);
> +	spin_unlock_irqrestore(&front_info->io_lock, flags);
> +
> +	if (ret == 0)
> +		ret = be_stream_wait_io(evtchnl);
> +
> +	mutex_unlock(&front_info->req_io_lock);
> +	return ret;
>  }
>  
>  static int be_page_flip(struct xen_drm_front_info *front_info, int conn_idx,
>  		uint64_t fb_cookie)
>  {
> -	return 0;
> +	struct xen_drm_front_evtchnl *evtchnl;
> +	struct xendispl_req *req;
> +	unsigned long flags;
> +	int ret;
> +
> +	if (unlikely(conn_idx >= front_info->num_evt_pairs))
> +		return -EINVAL;
> +
> +	dbuf_flush_fb(&front_info->dbuf_list, fb_cookie);
> +	evtchnl = &front_info->evt_pairs[conn_idx].req;
> +
> +	mutex_lock(&front_info->req_io_lock);
> +
> +	spin_lock_irqsave(&front_info->io_lock, flags);
> +	req = be_prepare_req(evtchnl, XENDISPL_OP_PG_FLIP);
> +	req->op.pg_flip.fb_cookie = fb_cookie;
> +
> +	ret = be_stream_do_io(evtchnl, req);
> +	spin_unlock_irqrestore(&front_info->io_lock, flags);
> +
> +	if (ret == 0)
> +		ret = be_stream_wait_io(evtchnl);
> +
> +	mutex_unlock(&front_info->req_io_lock);
> +	return ret;
>  }
>  
>  static void xen_drm_drv_unload(struct xen_drm_front_info *front_info)
> @@ -183,6 +497,7 @@ static void xen_drv_remove_internal(struct xen_drm_front_info *front_info)
>  {
>  	xen_drm_drv_deinit(front_info);
>  	xen_drm_front_evtchnl_free_all(front_info);
> +	dbuf_free_all(&front_info->dbuf_list);
>  }
>  
>  static int backend_on_initwait(struct xen_drm_front_info *front_info)
> @@ -310,6 +625,8 @@ static int xen_drv_probe(struct xenbus_device *xb_dev,
>  
>  	front_info->xb_dev = xb_dev;
>  	spin_lock_init(&front_info->io_lock);
> +	mutex_init(&front_info->req_io_lock);
> +	INIT_LIST_HEAD(&front_info->dbuf_list);
>  	front_info->drm_pdrv_registered = false;
>  	dev_set_drvdata(&xb_dev->dev, front_info);
>  	return xenbus_switch_state(xb_dev, XenbusStateInitialising);
> diff --git a/drivers/gpu/drm/xen/xen_drm_front.h b/drivers/gpu/drm/xen/xen_drm_front.h
> index c6f52c892434..db32d00145d1 100644
> --- a/drivers/gpu/drm/xen/xen_drm_front.h
> +++ b/drivers/gpu/drm/xen/xen_drm_front.h
> @@ -137,6 +137,8 @@ struct xen_drm_front_info {
>  	struct xenbus_device *xb_dev;
>  	/* to protect data between backend IO code and interrupt handler */
>  	spinlock_t io_lock;
> +	/* serializer for backend IO: request/response */
> +	struct mutex req_io_lock;
>  	bool drm_pdrv_registered;
>  	/* virtual DRM platform device */
>  	struct platform_device *drm_pdev;
> @@ -144,6 +146,9 @@ struct xen_drm_front_info {
>  	int num_evt_pairs;
>  	struct xen_drm_front_evtchnl_pair *evt_pairs;
>  	struct xen_drm_front_cfg cfg;
> +
> +	/* display buffers */
> +	struct list_head dbuf_list;
>  };
>  
>  #endif /* __XEN_DRM_FRONT_H_ */
> -- 
> 2.7.4
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch