drm/i915: Add intel_bo_panic_setup() and intel_bo_panic_finish()

Implement both functions for i915 and xe, they prepare the work for
drm_panic support.
They both use kmap_try_from_panic(), and map one page at a time, to
write the panic screen on the framebuffer.

Signed-off-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://lore.kernel.org/r/20250624091501.257661-8-jfalempe@redhat.com
Signed-off-by: Maarten Lankhorst <dev@lankhorst.se>

drivers/gpu/drm/i915/display/intel_bo.c

@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: MIT
 /* Copyright © 2024 Intel Corporation */
 
+#include <drm/drm_panic.h>
 #include "display/intel_display_types.h"
 #include "gem/i915_gem_mman.h"
 #include "gem/i915_gem_object.h"
@@ -63,3 +64,13 @@ struct intel_framebuffer *intel_bo_alloc_framebuffer(void)
 {
 	return i915_gem_object_alloc_framebuffer();
 }
+
+int intel_bo_panic_setup(struct drm_scanout_buffer *sb)
+{
+	return i915_gem_object_panic_setup(sb);
+}
+
+void intel_bo_panic_finish(struct intel_framebuffer *fb)
+{
+	return i915_gem_object_panic_finish(fb);
+}

drivers/gpu/drm/i915/display/intel_bo.h

@@ -7,6 +7,7 @@
 #include <linux/types.h>
 
 struct drm_gem_object;
+struct drm_scanout_buffer;
 struct intel_framebuffer;
 struct seq_file;
 struct vm_area_struct;
@@ -25,5 +26,7 @@ struct intel_frontbuffer *intel_bo_set_frontbuffer(struct drm_gem_object *obj,
 
 void intel_bo_describe(struct seq_file *m, struct drm_gem_object *obj);
 struct intel_framebuffer *intel_bo_alloc_framebuffer(void);
+int intel_bo_panic_setup(struct drm_scanout_buffer *sb);
+void intel_bo_panic_finish(struct intel_framebuffer *fb);
 
 #endif /* __INTEL_BO__ */

drivers/gpu/drm/i915/gem/i915_gem_object.h

@@ -16,6 +16,7 @@
 #include "i915_gem_ww.h"
 #include "i915_vma_types.h"
 
+struct drm_scanout_buffer;
 enum intel_region_id;
 struct intel_framebuffer;
 
@@ -693,6 +694,9 @@ int __i915_gem_object_put_pages(struct drm_i915_gem_object *obj);
 int i915_gem_object_truncate(struct drm_i915_gem_object *obj);
 
 struct intel_framebuffer *i915_gem_object_alloc_framebuffer(void);
+int i915_gem_object_panic_setup(struct drm_scanout_buffer *sb);
+void i915_gem_object_panic_finish(struct intel_framebuffer *fb);
+
 /**
  * i915_gem_object_pin_map - return a contiguous mapping of the entire object
  * @obj: the object to map into kernel address space

drivers/gpu/drm/i915/gem/i915_gem_pages.c

@@ -4,8 +4,10 @@
  */
 
 #include <drm/drm_cache.h>
+#include <drm/drm_panic.h>
 #include <linux/vmalloc.h>
 
+#include "display/intel_fb.h"
 #include "display/intel_display_types.h"
 #include "gt/intel_gt.h"
 #include "gt/intel_tlb.h"
@@ -366,6 +368,67 @@ struct i915_framebuffer {
 	struct i915_panic_data panic;
 };
 
+static inline struct i915_panic_data *to_i915_panic_data(struct intel_framebuffer *fb)
+{
+	return &container_of_const(fb, struct i915_framebuffer, base)->panic;
+}
+
+static void i915_panic_kunmap(struct i915_panic_data *panic)
+{
+	if (panic->vaddr) {
+		drm_clflush_virt_range(panic->vaddr, PAGE_SIZE);
+		kunmap_local(panic->vaddr);
+		panic->vaddr = NULL;
+	}
+}
+
+static struct page **i915_gem_object_panic_pages(struct drm_i915_gem_object *obj)
+{
+	unsigned long n_pages = obj->base.size >> PAGE_SHIFT, i;
+	struct page *page;
+	struct page **pages;
+	struct sgt_iter iter;
+
+	/* For a 3840x2160 32 bits Framebuffer, this should require ~64K */
+	pages = kmalloc_array(n_pages, sizeof(*pages), GFP_ATOMIC);
+	if (!pages)
+		return NULL;
+
+	i = 0;
+	for_each_sgt_page(page, iter, obj->mm.pages)
+		pages[i++] = page;
+	return pages;
+}
+
+/*
+ * The scanout buffer pages are not mapped, so for each pixel,
+ * use kmap_local_page_try_from_panic() to map the page, and write the pixel.
+ * Try to keep the map from the previous pixel, to avoid too much map/unmap.
+ */
+static void i915_gem_object_panic_page_set_pixel(struct drm_scanout_buffer *sb, unsigned int x,
+						 unsigned int y, u32 color)
+{
+	unsigned int new_page;
+	unsigned int offset;
+	struct intel_framebuffer *fb = (struct intel_framebuffer *)sb->private;
+	struct i915_panic_data *panic = to_i915_panic_data(fb);
+
+	offset = y * sb->pitch[0] + x * sb->format->cpp[0];
+
+	new_page = offset >> PAGE_SHIFT;
+	offset = offset % PAGE_SIZE;
+	if (new_page != panic->page) {
+		i915_panic_kunmap(panic);
+		panic->page = new_page;
+		panic->vaddr =
+			kmap_local_page_try_from_panic(panic->pages[panic->page]);
+	}
+	if (panic->vaddr) {
+		u32 *pix = panic->vaddr + offset;
+		*pix = color;
+	}
+}
+
 struct intel_framebuffer *i915_gem_object_alloc_framebuffer(void)
 {
 	struct i915_framebuffer *i915_fb;
@@ -376,6 +439,49 @@ struct intel_framebuffer *i915_gem_object_alloc_framebuffer(void)
 	return NULL;
 }
 
+/*
+ * Setup the gem framebuffer for drm_panic access.
+ * Use current vaddr if it exists, or setup a list of pages.
+ * pfn is not supported yet.
+ */
+int i915_gem_object_panic_setup(struct drm_scanout_buffer *sb)
+{
+	enum i915_map_type has_type;
+	struct intel_framebuffer *fb = (struct intel_framebuffer *)sb->private;
+	struct i915_panic_data *panic = to_i915_panic_data(fb);
+	struct drm_i915_gem_object *obj = to_intel_bo(intel_fb_bo(&fb->base));
+	void *ptr;
+
+	ptr = page_unpack_bits(obj->mm.mapping, &has_type);
+	if (ptr) {
+		if (i915_gem_object_has_iomem(obj))
+			iosys_map_set_vaddr_iomem(&sb->map[0], (void __iomem *)ptr);
+		else
+			iosys_map_set_vaddr(&sb->map[0], ptr);
+
+		return 0;
+	}
+	if (i915_gem_object_has_struct_page(obj)) {
+		panic->pages = i915_gem_object_panic_pages(obj);
+		if (!panic->pages)
+			return -ENOMEM;
+		panic->page = -1;
+		sb->set_pixel = i915_gem_object_panic_page_set_pixel;
+		return 0;
+	}
+	return -EOPNOTSUPP;
+}
+
+void i915_gem_object_panic_finish(struct intel_framebuffer *fb)
+{
+	struct i915_panic_data *panic = to_i915_panic_data(fb);
+
+	i915_panic_kunmap(panic);
+	panic->page = -1;
+	kfree(panic->pages);
+	panic->pages = NULL;
+}
+
 /* get, pin, and map the pages of the object into kernel space */
 void *i915_gem_object_pin_map(struct drm_i915_gem_object *obj,
 			      enum i915_map_type type)

drivers/gpu/drm/xe/display/intel_bo.c

@@ -1,8 +1,11 @@
 // SPDX-License-Identifier: MIT
 /* Copyright © 2024 Intel Corporation */
 
+#include <drm/drm_cache.h>
 #include <drm/drm_gem.h>
+#include <drm/drm_panic.h>
 
+#include "intel_fb.h"
 #include "intel_display_types.h"
 
 #include "xe_bo.h"
@@ -73,6 +76,50 @@ struct xe_framebuffer {
 	struct xe_panic_data panic;
 };
 
+static inline struct xe_panic_data *to_xe_panic_data(struct intel_framebuffer *fb)
+{
+	return &container_of_const(fb, struct xe_framebuffer, base)->panic;
+}
+
+static void xe_panic_kunmap(struct xe_panic_data *panic)
+{
+	if (panic->vaddr) {
+		drm_clflush_virt_range(panic->vaddr, PAGE_SIZE);
+		kunmap_local(panic->vaddr);
+		panic->vaddr = NULL;
+	}
+}
+
+/*
+ * The scanout buffer pages are not mapped, so for each pixel,
+ * use kmap_local_page_try_from_panic() to map the page, and write the pixel.
+ * Try to keep the map from the previous pixel, to avoid too much map/unmap.
+ */
+static void xe_panic_page_set_pixel(struct drm_scanout_buffer *sb, unsigned int x,
+				    unsigned int y, u32 color)
+{
+	struct intel_framebuffer *fb = (struct intel_framebuffer *)sb->private;
+	struct xe_panic_data *panic = to_xe_panic_data(fb);
+	struct xe_bo *bo = gem_to_xe_bo(intel_fb_bo(&fb->base));
+	unsigned int new_page;
+	unsigned int offset;
+
+	offset = y * sb->pitch[0] + x * sb->format->cpp[0];
+
+	new_page = offset >> PAGE_SHIFT;
+	offset = offset % PAGE_SIZE;
+	if (new_page != panic->page) {
+		xe_panic_kunmap(panic);
+		panic->page = new_page;
+		panic->vaddr = ttm_bo_kmap_try_from_panic(&bo->ttm,
+							  panic->page);
+	}
+	if (panic->vaddr) {
+		u32 *pix = panic->vaddr + offset;
+		*pix = color;
+	}
+}
+
 struct intel_framebuffer *intel_bo_alloc_framebuffer(void)
 {
 	struct xe_framebuffer *xe_fb;
@@ -83,3 +130,20 @@ struct intel_framebuffer *intel_bo_alloc_framebuffer(void)
 	return NULL;
 }
 
+int intel_bo_panic_setup(struct drm_scanout_buffer *sb)
+{
+	struct intel_framebuffer *fb = (struct intel_framebuffer *)sb->private;
+	struct xe_panic_data *panic = to_xe_panic_data(fb);
+
+	panic->page = -1;
+	sb->set_pixel = xe_panic_page_set_pixel;
+	return 0;
+}
+
+void intel_bo_panic_finish(struct intel_framebuffer *fb)
+{
+	struct xe_panic_data *panic = to_xe_panic_data(fb);
+
+	xe_panic_kunmap(panic);
+	panic->page = -1;
+}