[PATCH 6/9] drm/xen-front: Introduce DRM/KMS virtual display driver

[Oleksandr Andrushchenko <andr2000@gmail.com>]

From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>

Implement essential initialization of the display driver:
  - introduce required data structures
  - handle DRM/KMS driver registration
  - perform basic DRM driver initialization
  - register driver on backend connection
  - remove driver on backend disconnect
  - introduce essential callbacks required by DRM/KMS core
  - introduce essential callbacks required for frontend operations

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
---
 drivers/gpu/drm/xen/Makefile            |   1 +
 drivers/gpu/drm/xen/xen_drm_front.c     | 169 ++++++++++++++++++++++++-
 drivers/gpu/drm/xen/xen_drm_front.h     |  24 ++++
 drivers/gpu/drm/xen/xen_drm_front_drv.c | 211 ++++++++++++++++++++++++++++++++
 drivers/gpu/drm/xen/xen_drm_front_drv.h |  60 +++++++++
 5 files changed, 462 insertions(+), 3 deletions(-)
 create mode 100644 drivers/gpu/drm/xen/xen_drm_front_drv.c
 create mode 100644 drivers/gpu/drm/xen/xen_drm_front_drv.h

diff --git a/drivers/gpu/drm/xen/Makefile b/drivers/gpu/drm/xen/Makefile
index f1823cb596c5..d3068202590f 100644
--- a/drivers/gpu/drm/xen/Makefile
+++ b/drivers/gpu/drm/xen/Makefile
@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 
 drm_xen_front-objs := xen_drm_front.o \
+		      xen_drm_front_drv.o \
 		      xen_drm_front_evtchnl.o \
 		      xen_drm_front_shbuf.o \
 		      xen_drm_front_cfg.o
diff --git a/drivers/gpu/drm/xen/xen_drm_front.c b/drivers/gpu/drm/xen/xen_drm_front.c
index 0d94ff272da3..8de88e359d5e 100644
--- a/drivers/gpu/drm/xen/xen_drm_front.c
+++ b/drivers/gpu/drm/xen/xen_drm_front.c
@@ -18,6 +18,8 @@
 
 #include <drm/drmP.h>
 
+#include <linux/of_device.h>
+
 #include <xen/platform_pci.h>
 #include <xen/xen.h>
 #include <xen/xenbus.h>
@@ -25,15 +27,161 @@
 #include <xen/interface/io/displif.h>
 
 #include "xen_drm_front.h"
+#include "xen_drm_front_drv.h"
 #include "xen_drm_front_evtchnl.h"
 #include "xen_drm_front_shbuf.h"
 
+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;
+}
+
+static int be_dbuf_create_int(struct xen_drm_front_info *front_info,
+		uint64_t dbuf_cookie, uint32_t width, uint32_t height,
+		uint32_t bpp, uint64_t size, struct page **pages,
+		struct sg_table *sgt)
+{
+	return 0;
+}
+
+static int be_dbuf_create_from_sgt(struct xen_drm_front_info *front_info,
+		uint64_t dbuf_cookie, uint32_t width, uint32_t height,
+		uint32_t bpp, uint64_t size, struct sg_table *sgt)
+{
+	return be_dbuf_create_int(front_info, dbuf_cookie, width, height,
+			bpp, size, NULL, sgt);
+}
+
+static int be_dbuf_create_from_pages(struct xen_drm_front_info *front_info,
+		uint64_t dbuf_cookie, uint32_t width, uint32_t height,
+		uint32_t bpp, uint64_t size, struct page **pages)
+{
+	return be_dbuf_create_int(front_info, dbuf_cookie, width, height,
+			bpp, size, pages, NULL);
+}
+
+static int be_dbuf_destroy(struct xen_drm_front_info *front_info,
+		uint64_t dbuf_cookie)
+{
+	return 0;
+}
+
+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;
+}
+
+static int be_fb_detach(struct xen_drm_front_info *front_info,
+		uint64_t fb_cookie)
+{
+	return 0;
+}
+
+static int be_page_flip(struct xen_drm_front_info *front_info, int conn_idx,
+		uint64_t fb_cookie)
+{
+	return 0;
+}
+
+static void xen_drm_drv_unload(struct xen_drm_front_info *front_info)
+{
+	if (front_info->xb_dev->state != XenbusStateReconfiguring)
+		return;
+
+	DRM_DEBUG("Can try removing driver now\n");
+	xenbus_switch_state(front_info->xb_dev, XenbusStateInitialising);
+}
+
 static struct xen_drm_front_ops front_ops = {
-	/* placeholder for now */
+	.mode_set = be_mode_set,
+	.dbuf_create_from_pages = be_dbuf_create_from_pages,
+	.dbuf_create_from_sgt = be_dbuf_create_from_sgt,
+	.dbuf_destroy = be_dbuf_destroy,
+	.fb_attach = be_fb_attach,
+	.fb_detach = be_fb_detach,
+	.page_flip = be_page_flip,
+	.drm_last_close = xen_drm_drv_unload,
+};
+
+static int xen_drm_drv_probe(struct platform_device *pdev)
+{
+	/*
+	 * The device is not spawn from a device tree, so arch_setup_dma_ops
+	 * is not called, thus leaving the device with dummy DMA ops.
+	 * This makes the device return error on PRIME buffer import, which
+	 * is not correct: to fix this call of_dma_configure() with a NULL
+	 * node to set default DMA ops.
+	 */
+	of_dma_configure(&pdev->dev, NULL);
+	return xen_drm_front_drv_probe(pdev, &front_ops);
+}
+
+static int xen_drm_drv_remove(struct platform_device *pdev)
+{
+	return xen_drm_front_drv_remove(pdev);
+}
+
+struct platform_device_info xen_drm_front_platform_info = {
+	.name = XENDISPL_DRIVER_NAME,
+	.id = 0,
+	.num_res = 0,
+	.dma_mask = DMA_BIT_MASK(32),
 };
 
+static struct platform_driver xen_drm_front_front_info = {
+	.probe		= xen_drm_drv_probe,
+	.remove		= xen_drm_drv_remove,
+	.driver		= {
+		.name	= XENDISPL_DRIVER_NAME,
+	},
+};
+
+static void xen_drm_drv_deinit(struct xen_drm_front_info *front_info)
+{
+	if (!front_info->drm_pdrv_registered)
+		return;
+
+	if (front_info->drm_pdev)
+		platform_device_unregister(front_info->drm_pdev);
+
+	platform_driver_unregister(&xen_drm_front_front_info);
+	front_info->drm_pdrv_registered = false;
+	front_info->drm_pdev = NULL;
+}
+
+static int xen_drm_drv_init(struct xen_drm_front_info *front_info)
+{
+	int ret;
+
+	ret = platform_driver_register(&xen_drm_front_front_info);
+	if (ret < 0)
+		return ret;
+
+	front_info->drm_pdrv_registered = true;
+	/* pass card configuration via platform data */
+	xen_drm_front_platform_info.data = &front_info->cfg;
+	xen_drm_front_platform_info.size_data = sizeof(front_info->cfg);
+
+	front_info->drm_pdev = platform_device_register_full(
+			&xen_drm_front_platform_info);
+	if (IS_ERR_OR_NULL(front_info->drm_pdev)) {
+		DRM_ERROR("Failed to register " XENDISPL_DRIVER_NAME " PV DRM driver\n");
+		front_info->drm_pdev = NULL;
+		xen_drm_drv_deinit(front_info);
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
 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);
 }
 
@@ -59,13 +207,27 @@ static int backend_on_initwait(struct xen_drm_front_info *front_info)
 static int backend_on_connected(struct xen_drm_front_info *front_info)
 {
 	xen_drm_front_evtchnl_set_state(front_info, EVTCHNL_STATE_CONNECTED);
-	return 0;
+	return xen_drm_drv_init(front_info);
 }
 
 static void backend_on_disconnected(struct xen_drm_front_info *front_info)
 {
+	bool removed = true;
+
+	if (front_info->drm_pdev) {
+		if (xen_drm_front_drv_is_used(front_info->drm_pdev)) {
+			DRM_WARN("DRM driver still in use, deferring removal\n");
+			removed = false;
+		} else
+			xen_drv_remove_internal(front_info);
+	}
+
 	xen_drm_front_evtchnl_set_state(front_info, EVTCHNL_STATE_DISCONNECTED);
-	xenbus_switch_state(front_info->xb_dev, XenbusStateInitialising);
+
+	if (removed)
+		xenbus_switch_state(front_info->xb_dev, XenbusStateInitialising);
+	else
+		xenbus_switch_state(front_info->xb_dev, XenbusStateReconfiguring);
 }
 
 static void backend_on_changed(struct xenbus_device *xb_dev,
@@ -148,6 +310,7 @@ static int xen_drv_probe(struct xenbus_device *xb_dev,
 
 	front_info->xb_dev = xb_dev;
 	spin_lock_init(&front_info->io_lock);
+	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 13f22736ae02..9ed5bfb248d0 100644
--- a/drivers/gpu/drm/xen/xen_drm_front.h
+++ b/drivers/gpu/drm/xen/xen_drm_front.h
@@ -19,6 +19,8 @@
 #ifndef __XEN_DRM_FRONT_H_
 #define __XEN_DRM_FRONT_H_
 
+#include <linux/scatterlist.h>
+
 #include "xen_drm_front_cfg.h"
 
 #ifndef GRANT_INVALID_REF
@@ -30,16 +32,38 @@
 #define GRANT_INVALID_REF	0
 #endif
 
+struct xen_drm_front_drm_pipeline;
+
 struct xen_drm_front_ops {
+	int (*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);
+	int (*dbuf_create_from_pages)(struct xen_drm_front_info *front_info,
+			uint64_t dbuf_cookie, uint32_t width, uint32_t height,
+			uint32_t bpp, uint64_t size, struct page **pages);
+	int (*dbuf_create_from_sgt)(struct xen_drm_front_info *front_info,
+			uint64_t dbuf_cookie, uint32_t width, uint32_t height,
+			uint32_t bpp, uint64_t size, struct sg_table *sgt);
+	int (*dbuf_destroy)(struct xen_drm_front_info *front_info,
+			uint64_t dbuf_cookie);
+	int (*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);
+	int (*fb_detach)(struct xen_drm_front_info *front_info,
+			uint64_t fb_cookie);
+	int (*page_flip)(struct xen_drm_front_info *front_info,
+			int conn_idx, uint64_t fb_cookie);
 	/* CAUTION! this is called with a spin_lock held! */
 	void (*on_frame_done)(struct platform_device *pdev,
 			int conn_idx, uint64_t fb_cookie);
+	void (*drm_last_close)(struct xen_drm_front_info *front_info);
 };
 
 struct xen_drm_front_info {
 	struct xenbus_device *xb_dev;
 	/* to protect data between backend IO code and interrupt handler */
 	spinlock_t io_lock;
+	bool drm_pdrv_registered;
 	/* virtual DRM platform device */
 	struct platform_device *drm_pdev;
 
diff --git a/drivers/gpu/drm/xen/xen_drm_front_drv.c b/drivers/gpu/drm/xen/xen_drm_front_drv.c
new file mode 100644
index 000000000000..b3764d5ed0f6
--- /dev/null
+++ b/drivers/gpu/drm/xen/xen_drm_front_drv.c
@@ -0,0 +1,211 @@
+/*
+ *  Xen para-virtual DRM device
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation; either version 2 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ * Copyright (C) 2016-2018 EPAM Systems Inc.
+ *
+ * Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
+ */
+
+#include <drm/drmP.h>
+#include <drm/drm_gem.h>
+#include <drm/drm_atomic_helper.h>
+
+#include "xen_drm_front.h"
+#include "xen_drm_front_cfg.h"
+#include "xen_drm_front_drv.h"
+
+static int dumb_create(struct drm_file *filp,
+		struct drm_device *dev, struct drm_mode_create_dumb *args)
+{
+	return -EINVAL;
+}
+
+static void free_object(struct drm_gem_object *obj)
+{
+	struct xen_drm_front_drm_info *drm_info = obj->dev->dev_private;
+
+	drm_info->front_ops->dbuf_destroy(drm_info->front_info,
+			xen_drm_front_dbuf_to_cookie(obj));
+}
+
+static void on_frame_done(struct platform_device *pdev,
+		int conn_idx, uint64_t fb_cookie)
+{
+}
+
+static void lastclose(struct drm_device *dev)
+{
+	struct xen_drm_front_drm_info *drm_info = dev->dev_private;
+
+	drm_info->front_ops->drm_last_close(drm_info->front_info);
+}
+
+static int gem_mmap(struct file *filp, struct vm_area_struct *vma)
+{
+	return -EINVAL;
+}
+
+static struct sg_table *prime_get_sg_table(struct drm_gem_object *obj)
+{
+	return NULL;
+}
+
+static struct drm_gem_object *prime_import_sg_table(struct drm_device *dev,
+		struct dma_buf_attachment *attach, struct sg_table *sgt)
+{
+	return NULL;
+}
+
+static void *prime_vmap(struct drm_gem_object *obj)
+{
+	return NULL;
+}
+
+static void prime_vunmap(struct drm_gem_object *obj, void *vaddr)
+{
+}
+
+static int prime_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma)
+{
+	return -EINVAL;
+}
+
+static const struct file_operations xendrm_fops = {
+	.owner          = THIS_MODULE,
+	.open           = drm_open,
+	.release        = drm_release,
+	.unlocked_ioctl = drm_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl   = drm_compat_ioctl,
+#endif
+	.poll           = drm_poll,
+	.read           = drm_read,
+	.llseek         = no_llseek,
+	.mmap           = gem_mmap,
+};
+
+static const struct vm_operations_struct xen_drm_vm_ops = {
+	.open           = drm_gem_vm_open,
+	.close          = drm_gem_vm_close,
+};
+
+struct drm_driver xen_drm_driver = {
+	.driver_features           = DRIVER_GEM | DRIVER_MODESET |
+				     DRIVER_PRIME | DRIVER_ATOMIC,
+	.lastclose                 = lastclose,
+	.gem_free_object_unlocked  = free_object,
+	.gem_vm_ops                = &xen_drm_vm_ops,
+	.prime_handle_to_fd        = drm_gem_prime_handle_to_fd,
+	.prime_fd_to_handle        = drm_gem_prime_fd_to_handle,
+	.gem_prime_import          = drm_gem_prime_import,
+	.gem_prime_export          = drm_gem_prime_export,
+	.gem_prime_get_sg_table    = prime_get_sg_table,
+	.gem_prime_import_sg_table = prime_import_sg_table,
+	.gem_prime_vmap            = prime_vmap,
+	.gem_prime_vunmap          = prime_vunmap,
+	.gem_prime_mmap            = prime_mmap,
+	.dumb_create               = dumb_create,
+	.fops                      = &xendrm_fops,
+	.name                      = "xendrm-du",
+	.desc                      = "Xen PV DRM Display Unit",
+	.date                      = "20161109",
+	.major                     = 1,
+	.minor                     = 0,
+};
+
+int xen_drm_front_drv_probe(struct platform_device *pdev,
+		struct xen_drm_front_ops *front_ops)
+{
+	struct xen_drm_front_cfg *cfg = dev_get_platdata(&pdev->dev);
+	struct xen_drm_front_drm_info *drm_info;
+	struct drm_device *dev;
+	int ret;
+
+	DRM_INFO("Creating %s\n", xen_drm_driver.desc);
+
+	drm_info = devm_kzalloc(&pdev->dev, sizeof(*drm_info), GFP_KERNEL);
+	if (!drm_info)
+		return -ENOMEM;
+
+	drm_info->front_ops = front_ops;
+	drm_info->front_ops->on_frame_done = on_frame_done;
+	drm_info->front_info = cfg->front_info;
+
+	dev = drm_dev_alloc(&xen_drm_driver, &pdev->dev);
+	if (!dev)
+		return -ENOMEM;
+
+	drm_info->drm_dev = dev;
+
+	drm_info->cfg = cfg;
+	dev->dev_private = drm_info;
+	platform_set_drvdata(pdev, drm_info);
+
+	ret = drm_vblank_init(dev, cfg->num_connectors);
+	if (ret) {
+		DRM_ERROR("Failed to initialize vblank, ret %d\n", ret);
+		return ret;
+	}
+
+	dev->irq_enabled = 1;
+
+	ret = drm_dev_register(dev, 0);
+	if (ret)
+		goto fail_register;
+
+	DRM_INFO("Initialized %s %d.%d.%d %s on minor %d\n",
+			xen_drm_driver.name, xen_drm_driver.major,
+			xen_drm_driver.minor, xen_drm_driver.patchlevel,
+			xen_drm_driver.date, dev->primary->index);
+
+	return 0;
+
+fail_register:
+	drm_dev_unregister(dev);
+	drm_mode_config_cleanup(dev);
+	return ret;
+}
+
+int xen_drm_front_drv_remove(struct platform_device *pdev)
+{
+	struct xen_drm_front_drm_info *drm_info = platform_get_drvdata(pdev);
+	struct drm_device *dev = drm_info->drm_dev;
+
+	if (dev) {
+		drm_dev_unregister(dev);
+		drm_atomic_helper_shutdown(dev);
+		drm_mode_config_cleanup(dev);
+		drm_dev_unref(dev);
+	}
+	return 0;
+}
+
+bool xen_drm_front_drv_is_used(struct platform_device *pdev)
+{
+	struct xen_drm_front_drm_info *drm_info = platform_get_drvdata(pdev);
+	struct drm_device *dev;
+
+	if (!drm_info)
+		return false;
+
+	dev = drm_info->drm_dev;
+	if (!dev)
+		return false;
+
+	/*
+	 * FIXME: the code below must be protected by drm_global_mutex,
+	 * but it is not accessible to us. Anyways there is a race condition,
+	 * but we will re-try.
+	 */
+	return dev->open_count != 0;
+}
diff --git a/drivers/gpu/drm/xen/xen_drm_front_drv.h b/drivers/gpu/drm/xen/xen_drm_front_drv.h
new file mode 100644
index 000000000000..aaa476535c13
--- /dev/null
+++ b/drivers/gpu/drm/xen/xen_drm_front_drv.h
@@ -0,0 +1,60 @@
+/*
+ *  Xen para-virtual DRM device
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation; either version 2 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ * Copyright (C) 2016-2018 EPAM Systems Inc.
+ *
+ * Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
+ */
+
+#ifndef __XEN_DRM_FRONT_DRV_H_
+#define __XEN_DRM_FRONT_DRV_H_
+
+#include <drm/drmP.h>
+
+#include "xen_drm_front.h"
+#include "xen_drm_front_cfg.h"
+
+struct xen_drm_front_drm_pipeline {
+	struct xen_drm_front_drm_info *drm_info;
+
+	int index;
+};
+
+struct xen_drm_front_drm_info {
+	struct xen_drm_front_info *front_info;
+	struct xen_drm_front_ops *front_ops;
+	struct drm_device *drm_dev;
+	struct xen_drm_front_cfg *cfg;
+};
+
+static inline uint64_t xen_drm_front_fb_to_cookie(
+		struct drm_framebuffer *fb)
+{
+	return (uint64_t)fb;
+}
+
+static inline uint64_t xen_drm_front_dbuf_to_cookie(
+		struct drm_gem_object *gem_obj)
+{
+	return (uint64_t)gem_obj;
+}
+
+int xen_drm_front_drv_probe(struct platform_device *pdev,
+		struct xen_drm_front_ops *front_ops);
+
+int xen_drm_front_drv_remove(struct platform_device *pdev);
+
+bool xen_drm_front_drv_is_used(struct platform_device *pdev);
+
+#endif /* __XEN_DRM_FRONT_DRV_H_ */
+
-- 
2.7.4