From: Oleksandr Andrushchenko <oleksandr_andrushche...@epam.com>

Handle Xen event channels:
  - create for all configured connectors and publish
    corresponding ring references and event channels in Xen store,
    so backend can connect
  - implement event channels interrupt handlers
  - create and destroy event channels with respect to Xen bus state

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushche...@epam.com>
---
 drivers/gpu/drm/xen/Makefile                |   1 +
 drivers/gpu/drm/xen/xen_drm_front.c         |  12 +-
 drivers/gpu/drm/xen/xen_drm_front.h         |  16 ++
 drivers/gpu/drm/xen/xen_drm_front_evtchnl.c | 381 ++++++++++++++++++++++++++++
 drivers/gpu/drm/xen/xen_drm_front_evtchnl.h |  79 ++++++
 5 files changed, 488 insertions(+), 1 deletion(-)
 create mode 100644 drivers/gpu/drm/xen/xen_drm_front_evtchnl.c
 create mode 100644 drivers/gpu/drm/xen/xen_drm_front_evtchnl.h

diff --git a/drivers/gpu/drm/xen/Makefile b/drivers/gpu/drm/xen/Makefile
index d3ec8c8589e0..8417332f3b58 100644
--- a/drivers/gpu/drm/xen/Makefile
+++ b/drivers/gpu/drm/xen/Makefile
@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0 OR MIT
 
 drm_xen_front-objs := xen_drm_front.o \
+                     xen_drm_front_evtchnl.o \
                      xen_drm_front_cfg.o
 
 obj-$(CONFIG_DRM_XEN_FRONTEND) += drm_xen_front.o
diff --git a/drivers/gpu/drm/xen/xen_drm_front.c 
b/drivers/gpu/drm/xen/xen_drm_front.c
index ca42ceb24a40..8312dab862e2 100644
--- a/drivers/gpu/drm/xen/xen_drm_front.c
+++ b/drivers/gpu/drm/xen/xen_drm_front.c
@@ -17,9 +17,11 @@
 #include <xen/interface/io/displif.h>
 
 #include "xen_drm_front.h"
+#include "xen_drm_front_evtchnl.h"
 
 static void xen_drv_remove_internal(struct xen_drm_front_info *front_info)
 {
+       xen_drm_front_evtchnl_free_all(front_info);
 }
 
 static int displback_initwait(struct xen_drm_front_info *front_info)
@@ -33,16 +35,23 @@ static int displback_initwait(struct xen_drm_front_info 
*front_info)
                return ret;
 
        DRM_INFO("Have %d conector(s)\n", cfg->num_connectors);
-       return 0;
+       /* Create event channels for all connectors and publish */
+       ret = xen_drm_front_evtchnl_create_all(front_info);
+       if (ret < 0)
+               return ret;
+
+       return xen_drm_front_evtchnl_publish_all(front_info);
 }
 
 static int displback_connect(struct xen_drm_front_info *front_info)
 {
+       xen_drm_front_evtchnl_set_state(front_info, EVTCHNL_STATE_CONNECTED);
        return 0;
 }
 
 static void displback_disconnect(struct xen_drm_front_info *front_info)
 {
+       xen_drm_front_evtchnl_set_state(front_info, EVTCHNL_STATE_DISCONNECTED);
        xenbus_switch_state(front_info->xb_dev, XenbusStateInitialising);
 }
 
@@ -125,6 +134,7 @@ static int xen_drv_probe(struct xenbus_device *xb_dev,
                return -ENOMEM;
 
        front_info->xb_dev = xb_dev;
+       spin_lock_init(&front_info->io_lock);
        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 034a3987657e..4adb6101c889 100644
--- a/drivers/gpu/drm/xen/xen_drm_front.h
+++ b/drivers/gpu/drm/xen/xen_drm_front.h
@@ -13,8 +13,24 @@
 
 #include "xen_drm_front_cfg.h"
 
+#ifndef GRANT_INVALID_REF
+/*
+ * Note on usage of grant reference 0 as invalid grant reference:
+ * grant reference 0 is valid, but never exposed to a PV driver,
+ * because of the fact it is already in use/reserved by the PV console.
+ */
+#define GRANT_INVALID_REF      0
+#endif
+
 struct xen_drm_front_info {
        struct xenbus_device *xb_dev;
+       /* to protect data between backend IO code and interrupt handler */
+       spinlock_t io_lock;
+       /* virtual DRM platform device */
+       struct platform_device *drm_pdev;
+
+       int num_evt_pairs;
+       struct xen_drm_front_evtchnl_pair *evt_pairs;
        struct xen_drm_front_cfg cfg;
 };
 
diff --git a/drivers/gpu/drm/xen/xen_drm_front_evtchnl.c 
b/drivers/gpu/drm/xen/xen_drm_front_evtchnl.c
new file mode 100644
index 000000000000..fd9289a6a1c8
--- /dev/null
+++ b/drivers/gpu/drm/xen/xen_drm_front_evtchnl.c
@@ -0,0 +1,381 @@
+// SPDX-License-Identifier: GPL-2.0 OR MIT
+
+/*
+ *  Xen para-virtual DRM device
+ *
+ * Copyright (C) 2016-2018 EPAM Systems Inc.
+ *
+ * Author: Oleksandr Andrushchenko <oleksandr_andrushche...@epam.com>
+ */
+
+#include <drm/drmP.h>
+
+#include <linux/errno.h>
+#include <linux/irq.h>
+
+#include <xen/xenbus.h>
+#include <xen/events.h>
+#include <xen/grant_table.h>
+
+#include "xen_drm_front.h"
+#include "xen_drm_front_evtchnl.h"
+
+static irqreturn_t evtchnl_interrupt_ctrl(int irq, void *dev_id)
+{
+       struct xen_drm_front_evtchnl *evtchnl = dev_id;
+       struct xen_drm_front_info *front_info = evtchnl->front_info;
+       struct xendispl_resp *resp;
+       RING_IDX i, rp;
+       unsigned long flags;
+
+       if (unlikely(evtchnl->state != EVTCHNL_STATE_CONNECTED))
+               return IRQ_HANDLED;
+
+       spin_lock_irqsave(&front_info->io_lock, flags);
+
+again:
+       rp = evtchnl->u.req.ring.sring->rsp_prod;
+       /* ensure we see queued responses up to rp */
+       virt_rmb();
+
+       for (i = evtchnl->u.req.ring.rsp_cons; i != rp; i++) {
+               resp = RING_GET_RESPONSE(&evtchnl->u.req.ring, i);
+               if (unlikely(resp->id != evtchnl->evt_id))
+                       continue;
+
+               switch (resp->operation) {
+               case XENDISPL_OP_PG_FLIP:
+               case XENDISPL_OP_FB_ATTACH:
+               case XENDISPL_OP_FB_DETACH:
+               case XENDISPL_OP_DBUF_CREATE:
+               case XENDISPL_OP_DBUF_DESTROY:
+               case XENDISPL_OP_SET_CONFIG:
+                       evtchnl->u.req.resp_status = resp->status;
+                       complete(&evtchnl->u.req.completion);
+                       break;
+
+               default:
+                       DRM_ERROR("Operation %d is not supported\n",
+                               resp->operation);
+                       break;
+               }
+       }
+
+       evtchnl->u.req.ring.rsp_cons = i;
+
+       if (i != evtchnl->u.req.ring.req_prod_pvt) {
+               int more_to_do;
+
+               RING_FINAL_CHECK_FOR_RESPONSES(&evtchnl->u.req.ring,
+                               more_to_do);
+               if (more_to_do)
+                       goto again;
+       } else
+               evtchnl->u.req.ring.sring->rsp_event = i + 1;
+
+       spin_unlock_irqrestore(&front_info->io_lock, flags);
+       return IRQ_HANDLED;
+}
+
+static irqreturn_t evtchnl_interrupt_evt(int irq, void *dev_id)
+{
+       struct xen_drm_front_evtchnl *evtchnl = dev_id;
+       struct xen_drm_front_info *front_info = evtchnl->front_info;
+       struct xendispl_event_page *page = evtchnl->u.evt.page;
+       uint32_t cons, prod;
+       unsigned long flags;
+
+       if (unlikely(evtchnl->state != EVTCHNL_STATE_CONNECTED))
+               return IRQ_HANDLED;
+
+       spin_lock_irqsave(&front_info->io_lock, flags);
+
+       prod = page->in_prod;
+       /* ensure we see ring contents up to prod */
+       virt_rmb();
+       if (prod == page->in_cons)
+               goto out;
+
+       for (cons = page->in_cons; cons != prod; cons++) {
+               struct xendispl_evt *event;
+
+               event = &XENDISPL_IN_RING_REF(page, cons);
+               if (unlikely(event->id != evtchnl->evt_id++))
+                       continue;
+
+               switch (event->type) {
+               case XENDISPL_EVT_PG_FLIP:
+                       /* placeholder */
+                       break;
+               }
+       }
+       page->in_cons = cons;
+       /* ensure ring contents */
+       virt_wmb();
+
+out:
+       spin_unlock_irqrestore(&front_info->io_lock, flags);
+       return IRQ_HANDLED;
+}
+
+static void evtchnl_free(struct xen_drm_front_info *front_info,
+               struct xen_drm_front_evtchnl *evtchnl)
+{
+       unsigned long page = 0;
+
+       if (evtchnl->type == EVTCHNL_TYPE_REQ)
+               page = (unsigned long)evtchnl->u.req.ring.sring;
+       else if (evtchnl->type == EVTCHNL_TYPE_EVT)
+               page = (unsigned long)evtchnl->u.evt.page;
+       if (!page)
+               return;
+
+       evtchnl->state = EVTCHNL_STATE_DISCONNECTED;
+
+       if (evtchnl->type == EVTCHNL_TYPE_REQ) {
+               /* release all who still waits for response if any */
+               evtchnl->u.req.resp_status = -EIO;
+               complete_all(&evtchnl->u.req.completion);
+       }
+
+       if (evtchnl->irq)
+               unbind_from_irqhandler(evtchnl->irq, evtchnl);
+
+       if (evtchnl->port)
+               xenbus_free_evtchn(front_info->xb_dev, evtchnl->port);
+
+       /* end access and free the page */
+       if (evtchnl->gref != GRANT_INVALID_REF)
+               gnttab_end_foreign_access(evtchnl->gref, 0, page);
+
+       memset(evtchnl, 0, sizeof(*evtchnl));
+}
+
+static int evtchnl_alloc(struct xen_drm_front_info *front_info, int index,
+               struct xen_drm_front_evtchnl *evtchnl,
+               enum xen_drm_front_evtchnl_type type)
+{
+       struct xenbus_device *xb_dev = front_info->xb_dev;
+       unsigned long page;
+       grant_ref_t gref;
+       irq_handler_t handler;
+       int ret;
+
+       memset(evtchnl, 0, sizeof(*evtchnl));
+       evtchnl->type = type;
+       evtchnl->index = index;
+       evtchnl->front_info = front_info;
+       evtchnl->state = EVTCHNL_STATE_DISCONNECTED;
+       evtchnl->gref = GRANT_INVALID_REF;
+
+       page = get_zeroed_page(GFP_NOIO | __GFP_HIGH);
+       if (!page) {
+               ret = -ENOMEM;
+               goto fail;
+       }
+
+       if (type == EVTCHNL_TYPE_REQ) {
+               struct xen_displif_sring *sring;
+
+               init_completion(&evtchnl->u.req.completion);
+               sring = (struct xen_displif_sring *)page;
+               SHARED_RING_INIT(sring);
+               FRONT_RING_INIT(&evtchnl->u.req.ring,
+                               sring, XEN_PAGE_SIZE);
+
+               ret = xenbus_grant_ring(xb_dev, sring, 1, &gref);
+               if (ret < 0)
+                       goto fail;
+
+               handler = evtchnl_interrupt_ctrl;
+       } else {
+               evtchnl->u.evt.page = (struct xendispl_event_page *)page;
+
+               ret = gnttab_grant_foreign_access(xb_dev->otherend_id,
+                               virt_to_gfn((void *)page), 0);
+               if (ret < 0)
+                       goto fail;
+
+               gref = ret;
+               handler = evtchnl_interrupt_evt;
+       }
+       evtchnl->gref = gref;
+
+       ret = xenbus_alloc_evtchn(xb_dev, &evtchnl->port);
+       if (ret < 0)
+               goto fail;
+
+       ret = bind_evtchn_to_irqhandler(evtchnl->port,
+                       handler, 0, xb_dev->devicetype, evtchnl);
+       if (ret < 0)
+               goto fail;
+
+       evtchnl->irq = ret;
+       return 0;
+
+fail:
+       DRM_ERROR("Failed to allocate ring: %d\n", ret);
+       return ret;
+}
+
+int xen_drm_front_evtchnl_create_all(struct xen_drm_front_info *front_info)
+{
+       struct xen_drm_front_cfg *cfg;
+       int ret, conn;
+
+       cfg = &front_info->cfg;
+
+       front_info->evt_pairs = devm_kcalloc(&front_info->xb_dev->dev,
+                       cfg->num_connectors,
+                       sizeof(struct xen_drm_front_evtchnl_pair), GFP_KERNEL);
+       if (!front_info->evt_pairs) {
+               ret = -ENOMEM;
+               goto fail;
+       }
+
+       for (conn = 0; conn < cfg->num_connectors; conn++) {
+               ret = evtchnl_alloc(front_info, conn,
+                               &front_info->evt_pairs[conn].req,
+                               EVTCHNL_TYPE_REQ);
+               if (ret < 0) {
+                       DRM_ERROR("Error allocating control channel\n");
+                       goto fail;
+               }
+
+               ret = evtchnl_alloc(front_info, conn,
+                               &front_info->evt_pairs[conn].evt,
+                               EVTCHNL_TYPE_EVT);
+               if (ret < 0) {
+                       DRM_ERROR("Error allocating in-event channel\n");
+                       goto fail;
+               }
+       }
+       front_info->num_evt_pairs = cfg->num_connectors;
+       return 0;
+
+fail:
+       xen_drm_front_evtchnl_free_all(front_info);
+       return ret;
+}
+
+static int evtchnl_publish(struct xenbus_transaction xbt,
+               struct xen_drm_front_evtchnl *evtchnl, const char *path,
+               const char *node_ring, const char *node_chnl)
+{
+       struct xenbus_device *xb_dev = evtchnl->front_info->xb_dev;
+       int ret;
+
+       /* write control channel ring reference */
+       ret = xenbus_printf(xbt, path, node_ring, "%u", evtchnl->gref);
+       if (ret < 0) {
+               xenbus_dev_error(xb_dev, ret, "writing ring-ref");
+               return ret;
+       }
+
+       /* write event channel ring reference */
+       ret = xenbus_printf(xbt, path, node_chnl, "%u", evtchnl->port);
+       if (ret < 0) {
+               xenbus_dev_error(xb_dev, ret, "writing event channel");
+               return ret;
+       }
+
+       return 0;
+}
+
+int xen_drm_front_evtchnl_publish_all(struct xen_drm_front_info *front_info)
+{
+       struct xenbus_transaction xbt;
+       struct xen_drm_front_cfg *plat_data;
+       int ret, conn;
+
+       plat_data = &front_info->cfg;
+
+again:
+       ret = xenbus_transaction_start(&xbt);
+       if (ret < 0) {
+               xenbus_dev_fatal(front_info->xb_dev, ret,
+                               "starting transaction");
+               return ret;
+       }
+
+       for (conn = 0; conn < plat_data->num_connectors; conn++) {
+               ret = evtchnl_publish(xbt,
+                               &front_info->evt_pairs[conn].req,
+                               plat_data->connectors[conn].xenstore_path,
+                               XENDISPL_FIELD_REQ_RING_REF,
+                               XENDISPL_FIELD_REQ_CHANNEL);
+               if (ret < 0)
+                       goto fail;
+
+               ret = evtchnl_publish(xbt,
+                               &front_info->evt_pairs[conn].evt,
+                               plat_data->connectors[conn].xenstore_path,
+                               XENDISPL_FIELD_EVT_RING_REF,
+                               XENDISPL_FIELD_EVT_CHANNEL);
+               if (ret < 0)
+                       goto fail;
+       }
+
+       ret = xenbus_transaction_end(xbt, 0);
+       if (ret < 0) {
+               if (ret == -EAGAIN)
+                       goto again;
+
+               xenbus_dev_fatal(front_info->xb_dev, ret,
+                               "completing transaction");
+               goto fail_to_end;
+       }
+
+       return 0;
+
+fail:
+       xenbus_transaction_end(xbt, 1);
+
+fail_to_end:
+       xenbus_dev_fatal(front_info->xb_dev, ret, "writing Xen store");
+       return ret;
+}
+
+void xen_drm_front_evtchnl_flush(struct xen_drm_front_evtchnl *evtchnl)
+{
+       int notify;
+
+       evtchnl->u.req.ring.req_prod_pvt++;
+       RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&evtchnl->u.req.ring, notify);
+       if (notify)
+               notify_remote_via_irq(evtchnl->irq);
+}
+
+void xen_drm_front_evtchnl_set_state(struct xen_drm_front_info *front_info,
+               enum xen_drm_front_evtchnl_state state)
+{
+       unsigned long flags;
+       int i;
+
+       if (!front_info->evt_pairs)
+               return;
+
+       spin_lock_irqsave(&front_info->io_lock, flags);
+       for (i = 0; i < front_info->num_evt_pairs; i++) {
+               front_info->evt_pairs[i].req.state = state;
+               front_info->evt_pairs[i].evt.state = state;
+       }
+       spin_unlock_irqrestore(&front_info->io_lock, flags);
+
+}
+
+void xen_drm_front_evtchnl_free_all(struct xen_drm_front_info *front_info)
+{
+       int i;
+
+       if (!front_info->evt_pairs)
+               return;
+
+       for (i = 0; i < front_info->num_evt_pairs; i++) {
+               evtchnl_free(front_info, &front_info->evt_pairs[i].req);
+               evtchnl_free(front_info, &front_info->evt_pairs[i].evt);
+       }
+
+       devm_kfree(&front_info->xb_dev->dev, front_info->evt_pairs);
+       front_info->evt_pairs = NULL;
+}
diff --git a/drivers/gpu/drm/xen/xen_drm_front_evtchnl.h 
b/drivers/gpu/drm/xen/xen_drm_front_evtchnl.h
new file mode 100644
index 000000000000..8faacf9444e6
--- /dev/null
+++ b/drivers/gpu/drm/xen/xen_drm_front_evtchnl.h
@@ -0,0 +1,79 @@
+/* SPDX-License-Identifier: GPL-2.0 OR MIT */
+
+/*
+ *  Xen para-virtual DRM device
+ *
+ * Copyright (C) 2016-2018 EPAM Systems Inc.
+ *
+ * Author: Oleksandr Andrushchenko <oleksandr_andrushche...@epam.com>
+ */
+
+#ifndef __XEN_DRM_FRONT_EVTCHNL_H_
+#define __XEN_DRM_FRONT_EVTCHNL_H_
+
+#include <linux/completion.h>
+#include <linux/types.h>
+
+#include <xen/interface/io/ring.h>
+#include <xen/interface/io/displif.h>
+
+/*
+ * All operations which are not connector oriented use this ctrl event channel,
+ * e.g. fb_attach/destroy which belong to a DRM device, not to a CRTC.
+ */
+#define GENERIC_OP_EVT_CHNL    0
+
+enum xen_drm_front_evtchnl_state {
+       EVTCHNL_STATE_DISCONNECTED,
+       EVTCHNL_STATE_CONNECTED,
+};
+
+enum xen_drm_front_evtchnl_type {
+       EVTCHNL_TYPE_REQ,
+       EVTCHNL_TYPE_EVT,
+};
+
+struct xen_drm_front_drm_info;
+
+struct xen_drm_front_evtchnl {
+       struct xen_drm_front_info *front_info;
+       int gref;
+       int port;
+       int irq;
+       int index;
+       enum xen_drm_front_evtchnl_state state;
+       enum xen_drm_front_evtchnl_type type;
+       /* either response id or incoming event id */
+       uint16_t evt_id;
+       /* next request id or next expected event id */
+       uint16_t evt_next_id;
+       union {
+               struct {
+                       struct xen_displif_front_ring ring;
+                       struct completion completion;
+                       /* latest response status */
+                       int resp_status;
+               } req;
+               struct {
+                       struct xendispl_event_page *page;
+               } evt;
+       } u;
+};
+
+struct xen_drm_front_evtchnl_pair {
+       struct xen_drm_front_evtchnl req;
+       struct xen_drm_front_evtchnl evt;
+};
+
+int xen_drm_front_evtchnl_create_all(struct xen_drm_front_info *front_info);
+
+int xen_drm_front_evtchnl_publish_all(struct xen_drm_front_info *front_info);
+
+void xen_drm_front_evtchnl_flush(struct xen_drm_front_evtchnl *evtchnl);
+
+void xen_drm_front_evtchnl_set_state(struct xen_drm_front_info *front_info,
+               enum xen_drm_front_evtchnl_state state);
+
+void xen_drm_front_evtchnl_free_all(struct xen_drm_front_info *front_info);
+
+#endif /* __XEN_DRM_FRONT_EVTCHNL_H_ */
-- 
2.7.4

Reply via email to