From: Oleksandr Andrushchenko oleksandr_andrushchenko@epam.com
Initial handling for Xen bus states: implement Xen bus state machine for the frontend driver according to the state diagram and recovery flow from display para-virtualized protocol: xen/interface/io/displif.h.
Signed-off-by: Oleksandr Andrushchenko oleksandr_andrushchenko@epam.com --- drivers/gpu/drm/xen/xen_drm_front.c | 124 +++++++++++++++++++++++++++++++++++- drivers/gpu/drm/xen/xen_drm_front.h | 18 ++++++ 2 files changed, 141 insertions(+), 1 deletion(-) create mode 100644 drivers/gpu/drm/xen/xen_drm_front.h
diff --git a/drivers/gpu/drm/xen/xen_drm_front.c b/drivers/gpu/drm/xen/xen_drm_front.c index 03bc50b128fd..520b5b34520b 100644 --- a/drivers/gpu/drm/xen/xen_drm_front.c +++ b/drivers/gpu/drm/xen/xen_drm_front.c @@ -16,19 +16,141 @@
#include <xen/interface/io/displif.h>
+#include "xen_drm_front.h" + +static void xen_drv_remove_internal(struct xen_drm_front_info *front_info) +{ +} + +static int displback_initwait(struct xen_drm_front_info *front_info) +{ + return 0; +} + +static int displback_connect(struct xen_drm_front_info *front_info) +{ + return 0; +} + +static void displback_disconnect(struct xen_drm_front_info *front_info) +{ + xenbus_switch_state(front_info->xb_dev, XenbusStateInitialising); +} + static void displback_changed(struct xenbus_device *xb_dev, enum xenbus_state backend_state) { + struct xen_drm_front_info *front_info = dev_get_drvdata(&xb_dev->dev); + int ret; + + DRM_DEBUG("Backend state is %s, front is %s\n", + xenbus_strstate(backend_state), + xenbus_strstate(xb_dev->state)); + + switch (backend_state) { + case XenbusStateReconfiguring: + /* fall through */ + case XenbusStateReconfigured: + /* fall through */ + case XenbusStateInitialised: + break; + + case XenbusStateInitialising: + /* recovering after backend unexpected closure */ + displback_disconnect(front_info); + break; + + case XenbusStateInitWait: + /* recovering after backend unexpected closure */ + displback_disconnect(front_info); + if (xb_dev->state != XenbusStateInitialising) + break; + + ret = displback_initwait(front_info); + if (ret < 0) + xenbus_dev_fatal(xb_dev, ret, + "initializing frontend"); + else + xenbus_switch_state(xb_dev, XenbusStateInitialised); + break; + + case XenbusStateConnected: + if (xb_dev->state != XenbusStateInitialised) + break; + + ret = displback_connect(front_info); + if (ret < 0) + xenbus_dev_fatal(xb_dev, ret, + "initializing DRM driver"); + else + xenbus_switch_state(xb_dev, XenbusStateConnected); + break; + + case XenbusStateClosing: + /* + * in this state backend starts freeing resources, + * so let it go into closed state, so we can also + * remove ours + */ + break; + + case XenbusStateUnknown: + /* fall through */ + case XenbusStateClosed: + if (xb_dev->state == XenbusStateClosed) + break; + + displback_disconnect(front_info); + break; + } }
static int xen_drv_probe(struct xenbus_device *xb_dev, const struct xenbus_device_id *id) { - return 0; + struct xen_drm_front_info *front_info; + + front_info = devm_kzalloc(&xb_dev->dev, + sizeof(*front_info), GFP_KERNEL); + if (!front_info) + return -ENOMEM; + + front_info->xb_dev = xb_dev; + dev_set_drvdata(&xb_dev->dev, front_info); + return xenbus_switch_state(xb_dev, XenbusStateInitialising); }
static int xen_drv_remove(struct xenbus_device *dev) { + struct xen_drm_front_info *front_info = dev_get_drvdata(&dev->dev); + int to = 100; + + xenbus_switch_state(dev, XenbusStateClosing); + + /* + * On driver removal it is disconnected from XenBus, + * so no backend state change events come via .otherend_changed + * callback. This prevents us from exiting gracefully, e.g. + * signaling the backend to free event channels, waiting for its + * state to change to XenbusStateClosed and cleaning at our end. + * Normally when front driver removed backend will finally go into + * XenbusStateInitWait state. + * + * Workaround: read backend's state manually and wait with time-out. + */ + while ((xenbus_read_unsigned(front_info->xb_dev->otherend, + "state", XenbusStateUnknown) != XenbusStateInitWait) && + to--) + msleep(10); + + if (!to) + DRM_ERROR("Backend state is %s while removing driver\n", + xenbus_strstate(xenbus_read_unsigned( + front_info->xb_dev->otherend, + "state", XenbusStateUnknown))); + + xen_drv_remove_internal(front_info); + xenbus_frontend_closed(dev); return 0; }
diff --git a/drivers/gpu/drm/xen/xen_drm_front.h b/drivers/gpu/drm/xen/xen_drm_front.h new file mode 100644 index 000000000000..8b8d4d1e0816 --- /dev/null +++ b/drivers/gpu/drm/xen/xen_drm_front.h @@ -0,0 +1,18 @@ +/* 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_H_ +#define __XEN_DRM_FRONT_H_ + +struct xen_drm_front_info { + struct xenbus_device *xb_dev; +}; + +#endif /* __XEN_DRM_FRONT_H_ */