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Subject[PATCH v2 4/8] drm/xen-front: Implement Xen event channel handling
Date
From: Oleksandr Andrushchenko <oleksandr_andrushchenko@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_andrushchenko@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_andrushchenko@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_andrushchenko@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
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