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Subject[PATCH 9/9] drm/xen-front: Implement communication with backend
Date
From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>

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@epam.com>
---
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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