drm/xe: Introduce a new DRM driver for Intel GPUs

Xe, is a new driver for Intel GPUs that supports both integrated and
discrete platforms starting with Tiger Lake (first Intel Xe Architecture).

The code is at a stage where it is already functional and has experimental
support for multiple platforms starting from Tiger Lake, with initial
support implemented in Mesa (for Iris and Anv, our OpenGL and Vulkan
drivers), as well as in NEO (for OpenCL and Level0).

The new Xe driver leverages a lot from i915.

As for display, the intent is to share the display code with the i915
driver so that there is maximum reuse there. But it is not added
in this patch.

This initial work is a collaboration of many people and unfortunately
the big squashed patch won't fully honor the proper credits. But let's
get some git quick stats so we can at least try to preserve some of the
credits:

Co-developed-by: Matthew Brost <matthew.brost@intel.com>
Co-developed-by: Matthew Auld <matthew.auld@intel.com>
Co-developed-by: Matt Roper <matthew.d.roper@intel.com>
Co-developed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Co-developed-by: Francois Dugast <francois.dugast@intel.com>
Co-developed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Co-developed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Co-developed-by: Philippe Lecluse <philippe.lecluse@intel.com>
Co-developed-by: Nirmoy Das <nirmoy.das@intel.com>
Co-developed-by: Jani Nikula <jani.nikula@intel.com>
Co-developed-by: José Roberto de Souza <jose.souza@intel.com>
Co-developed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Co-developed-by: Dave Airlie <airlied@redhat.com>
Co-developed-by: Faith Ekstrand <faith.ekstrand@collabora.com>
Co-developed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Co-developed-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>

1 files changed, 160 insertions, 0 deletions

diff --git a/drivers/gpu/drm/xe/xe_pt_walk.c b/drivers/gpu/drm/xe/xe_pt_walk.c
new file mode 100644
index 000000000000..0def89af4372
--- /dev/null
+++ b/drivers/gpu/drm/xe/xe_pt_walk.c
@@ -0,0 +1,160 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright © 2022 Intel Corporation
+ */
+#include "xe_pt_walk.h"
+
+/**
+ * DOC: GPU page-table tree walking.
+ * The utilities in this file are similar to the CPU page-table walk
+ * utilities in mm/pagewalk.c. The main difference is that we distinguish
+ * the various levels of a page-table tree with an unsigned integer rather
+ * than by name. 0 is the lowest level, and page-tables with level 0 can
+ * not be directories pointing to lower levels, whereas all other levels
+ * can. The user of the utilities determines the highest level.
+ *
+ * Nomenclature:
+ * Each struct xe_ptw, regardless of level is referred to as a page table, and
+ * multiple page tables typically form a page table tree with page tables at
+ * intermediate levels being page directories pointing at page tables at lower
+ * levels. A shared page table for a given address range is a page-table which
+ * is neither fully within nor fully outside the address range and that can
+ * thus be shared by two or more address ranges.
+ *
+ * Please keep this code generic so that it can used as a drm-wide page-
+ * table walker should other drivers find use for it.
+ */
+static u64 xe_pt_addr_end(u64 addr, u64 end, unsigned int level,
+			  const struct xe_pt_walk *walk)
+{
+	u64 size = 1ull << walk->shifts[level];
+	u64 tmp = round_up(addr + 1, size);
+
+	return min_t(u64, tmp, end);
+}
+
+static bool xe_pt_next(pgoff_t *offset, u64 *addr, u64 next, u64 end,
+		       unsigned int level, const struct xe_pt_walk *walk)
+{
+	pgoff_t step = 1;
+
+	/* Shared pt walk skips to the last pagetable */
+	if (unlikely(walk->shared_pt_mode)) {
+		unsigned int shift = walk->shifts[level];
+		u64 skip_to = round_down(end, 1ull << shift);
+
+		if (skip_to > next) {
+			step += (skip_to - next) >> shift;
+			next = skip_to;
+		}
+	}
+
+	*addr = next;
+	*offset += step;
+
+	return next != end;
+}
+
+/**
+ * xe_pt_walk_range() - Walk a range of a gpu page table tree with callbacks
+ * for each page-table entry in all levels.
+ * @parent: The root page table for walk start.
+ * @level: The root page table level.
+ * @addr: Virtual address start.
+ * @end: Virtual address end + 1.
+ * @walk: Walk info.
+ *
+ * Similar to the CPU page-table walker, this is a helper to walk
+ * a gpu page table and call a provided callback function for each entry.
+ *
+ * Return: 0 on success, negative error code on error. The error is
+ * propagated from the callback and on error the walk is terminated.
+ */
+int xe_pt_walk_range(struct xe_ptw *parent, unsigned int level,
+		     u64 addr, u64 end, struct xe_pt_walk *walk)
+{
+	pgoff_t offset = xe_pt_offset(addr, level, walk);
+	struct xe_ptw **entries = parent->dir ? parent->dir->entries : NULL;
+	const struct xe_pt_walk_ops *ops = walk->ops;
+	enum page_walk_action action;
+	struct xe_ptw *child;
+	int err = 0;
+	u64 next;
+
+	do {
+		next = xe_pt_addr_end(addr, end, level, walk);
+		if (walk->shared_pt_mode && xe_pt_covers(addr, next, level,
+							 walk))
+			continue;
+again:
+		action = ACTION_SUBTREE;
+		child = entries ? entries[offset] : NULL;
+		err = ops->pt_entry(parent, offset, level, addr, next,
+				    &child, &action, walk);
+		if (err)
+			break;
+
+		/* Probably not needed yet for gpu pagetable walk. */
+		if (unlikely(action == ACTION_AGAIN))
+			goto again;
+
+		if (likely(!level || !child || action == ACTION_CONTINUE))
+			continue;
+
+		err = xe_pt_walk_range(child, level - 1, addr, next, walk);
+
+		if (!err && ops->pt_post_descend)
+			err = ops->pt_post_descend(parent, offset, level, addr,
+						   next, &child, &action, walk);
+		if (err)
+			break;
+
+	} while (xe_pt_next(&offset, &addr, next, end, level, walk));
+
+	return err;
+}
+
+/**
+ * xe_pt_walk_shared() - Walk shared page tables of a page-table tree.
+ * @parent: Root page table directory.
+ * @level: Level of the root.
+ * @addr: Start address.
+ * @end: Last address + 1.
+ * @walk: Walk info.
+ *
+ * This function is similar to xe_pt_walk_range() but it skips page tables
+ * that are private to the range. Since the root (or @parent) page table is
+ * typically also a shared page table this function is different in that it
+ * calls the pt_entry callback and the post_descend callback also for the
+ * root. The root can be detected in the callbacks by checking whether
+ * parent == *child.
+ * Walking only the shared page tables is common for unbind-type operations
+ * where the page-table entries for an address range are cleared or detached
+ * from the main page-table tree.
+ *
+ * Return: 0 on success, negative error code on error: If a callback
+ * returns an error, the walk will be terminated and the error returned by
+ * this function.
+ */
+int xe_pt_walk_shared(struct xe_ptw *parent, unsigned int level,
+		      u64 addr, u64 end, struct xe_pt_walk *walk)
+{
+	const struct xe_pt_walk_ops *ops = walk->ops;
+	enum page_walk_action action = ACTION_SUBTREE;
+	struct xe_ptw *child = parent;
+	int err;
+
+	walk->shared_pt_mode = true;
+	err = walk->ops->pt_entry(parent, 0, level + 1, addr, end,
+				  &child, &action, walk);
+
+	if (err || action != ACTION_SUBTREE)
+		return err;
+
+	err = xe_pt_walk_range(parent, level, addr, end, walk);
+	if (!err && ops->pt_post_descend) {
+		err = ops->pt_post_descend(parent, 0, level + 1, addr, end,
+					   &child, &action, walk);
+	}
+	return err;
+}