1 files changed, 290 insertions, 0 deletions
diff --git a/drivers/gpu/drm/drm_panic.c b/drivers/gpu/drm/drm_panic.c
new file mode 100644
index 000000000000..7c81b3d73239
--- /dev/null
+++ b/drivers/gpu/drm/drm_panic.c
@@ -0,0 +1,290 @@
+// SPDX-License-Identifier: GPL-2.0 or MIT
+/*
+ * Copyright (c) 2023 Red Hat.
+ * Author: Jocelyn Falempe <jfalempe@redhat.com>
+ * inspired by the drm_log driver from David Herrmann <dh.herrmann@gmail.com>
+ * Tux Ascii art taken from cowsay written by Tony Monroe
+ */
+
+#include <linux/font.h>
+#include <linux/iosys-map.h>
+#include <linux/kdebug.h>
+#include <linux/kmsg_dump.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/types.h>
+
+#include <drm/drm_drv.h>
+#include <drm/drm_format_helper.h>
+#include <drm/drm_fourcc.h>
+#include <drm/drm_framebuffer.h>
+#include <drm/drm_modeset_helper_vtables.h>
+#include <drm/drm_panic.h>
+#include <drm/drm_plane.h>
+#include <drm/drm_print.h>
+
+MODULE_AUTHOR("Jocelyn Falempe");
+MODULE_DESCRIPTION("DRM panic handler");
+MODULE_LICENSE("GPL");
+
+/**
+ * DOC: overview
+ *
+ * To enable DRM panic for a driver, the primary plane must implement a
+ * &drm_plane_helper_funcs.get_scanout_buffer helper function. It is then
+ * automatically registered to the drm panic handler.
+ * When a panic occurs, the &drm_plane_helper_funcs.get_scanout_buffer will be
+ * called, and the driver can provide a framebuffer so the panic handler can
+ * draw the panic screen on it. Currently only linear buffer and a few color
+ * formats are supported.
+ * Optionally the driver can also provide a &drm_plane_helper_funcs.panic_flush
+ * callback, that will be called after that, to send additional commands to the
+ * hardware to make the scanout buffer visible.
+ */
+
+/*
+ * This module displays a user friendly message on screen when a kernel panic
+ * occurs. This is conflicting with fbcon, so you can only enable it when fbcon
+ * is disabled.
+ * It's intended for end-user, so have minimal technical/debug information.
+ *
+ * Implementation details:
+ *
+ * It is a panic handler, so it can't take lock, allocate memory, run tasks/irq,
+ * or attempt to sleep. It's a best effort, and it may not be able to display
+ * the message in all situations (like if the panic occurs in the middle of a
+ * modesetting).
+ * It will display only one static frame, so performance optimizations are low
+ * priority as the machine is already in an unusable state.
+ */
+
+struct drm_panic_line {
+	u32 len;
+	const char *txt;
+};
+
+#define PANIC_LINE(s) {.len = sizeof(s) - 1, .txt = s}
+
+static struct drm_panic_line panic_msg[] = {
+	PANIC_LINE("KERNEL PANIC !"),
+	PANIC_LINE(""),
+	PANIC_LINE("Please reboot your computer."),
+};
+
+static const struct drm_panic_line logo[] = {
+	PANIC_LINE("     .--.        _"),
+	PANIC_LINE("    |o_o |      | |"),
+	PANIC_LINE("    |:_/ |      | |"),
+	PANIC_LINE("   //   \\ \\     |_|"),
+	PANIC_LINE("  (|     | )     _"),
+	PANIC_LINE(" /'\\_   _/`\\    (_)"),
+	PANIC_LINE(" \\___)=(___/"),
+};
+
+static void drm_panic_fill32(struct iosys_map *map, unsigned int pitch,
+			     unsigned int height, unsigned int width,
+			     u32 color)
+{
+	unsigned int y, x;
+
+	for (y = 0; y < height; y++)
+		for (x = 0; x < width; x++)
+			iosys_map_wr(map, y * pitch + x * sizeof(u32), u32, color);
+}
+
+static void drm_panic_blit32(struct iosys_map *dmap, unsigned int dpitch,
+			     const u8 *sbuf8, unsigned int spitch,
+			     unsigned int height, unsigned int width,
+			     u32 fg32, u32 bg32)
+{
+	unsigned int y, x;
+	u32 val32;
+
+	for (y = 0; y < height; y++) {
+		for (x = 0; x < width; x++) {
+			val32 = (sbuf8[(y * spitch) + x / 8] & (0x80 >> (x % 8))) ? fg32 : bg32;
+			iosys_map_wr(dmap, y * dpitch + x * sizeof(u32), u32, val32);
+		}
+	}
+}
+
+static const u8 *get_char_bitmap(const struct font_desc *font, char c, size_t font_pitch)
+{
+	return font->data + (c * font->height) * font_pitch;
+}
+
+static unsigned int get_max_line_len(const struct drm_panic_line *lines, int len)
+{
+	int i;
+	unsigned int max = 0;
+
+	for (i = 0; i < len; i++)
+		max = max(lines[i].len, max);
+	return max;
+}
+
+/*
+ * Draw a text in a rectangle on a framebuffer. The text is truncated if it overflows the rectangle
+ */
+static void draw_txt_rectangle(struct drm_scanout_buffer *sb,
+			       const struct font_desc *font,
+			       const struct drm_panic_line *msg,
+			       unsigned int msg_lines,
+			       bool centered,
+			       struct drm_rect *clip,
+			       u32 fg_color,
+			       u32 bg_color)
+{
+	int i, j;
+	const u8 *src;
+	size_t font_pitch = DIV_ROUND_UP(font->width, 8);
+	struct iosys_map dst;
+	unsigned int px_width = sb->format->cpp[0];
+	int left = 0;
+
+	msg_lines = min(msg_lines,  drm_rect_height(clip) / font->height);
+	for (i = 0; i < msg_lines; i++) {
+		size_t line_len = min(msg[i].len, drm_rect_width(clip) / font->width);
+
+		if (centered)
+			left = (drm_rect_width(clip) - (line_len * font->width)) / 2;
+
+		dst = sb->map[0];
+		iosys_map_incr(&dst, (clip->y1 + i * font->height) * sb->pitch[0] +
+				     (clip->x1 + left) * px_width);
+		for (j = 0; j < line_len; j++) {
+			src = get_char_bitmap(font, msg[i].txt[j], font_pitch);
+			drm_panic_blit32(&dst, sb->pitch[0], src, font_pitch,
+					 font->height, font->width,
+					 fg_color, bg_color);
+			iosys_map_incr(&dst, font->width * px_width);
+		}
+	}
+}
+
+/*
+ * Draw the panic message at the center of the screen
+ */
+static void draw_panic_static(struct drm_scanout_buffer *sb)
+{
+	size_t msg_lines = ARRAY_SIZE(panic_msg);
+	size_t logo_lines = ARRAY_SIZE(logo);
+	u32 fg_color = CONFIG_DRM_PANIC_FOREGROUND_COLOR;
+	u32 bg_color = CONFIG_DRM_PANIC_BACKGROUND_COLOR;
+	const struct font_desc *font = get_default_font(sb->width, sb->height, NULL, NULL);
+	struct drm_rect r_logo, r_msg;
+
+	if (!font)
+		return;
+
+	r_logo = DRM_RECT_INIT(0, 0,
+			       get_max_line_len(logo, logo_lines) * font->width,
+			       logo_lines * font->height);
+	r_msg = DRM_RECT_INIT(0, 0,
+			      min(get_max_line_len(panic_msg, msg_lines) * font->width, sb->width),
+			      min(msg_lines * font->height, sb->height));
+
+	/* Center the panic message */
+	drm_rect_translate(&r_msg, (sb->width - r_msg.x2) / 2, (sb->height - r_msg.y2) / 2);
+
+	/* Fill with the background color, and draw text on top */
+	drm_panic_fill32(&sb->map[0], sb->pitch[0], sb->height, sb->width, bg_color);
+
+	if ((r_msg.x1 >= drm_rect_width(&r_logo) || r_msg.y1 >= drm_rect_height(&r_logo)) &&
+	    drm_rect_width(&r_logo) < sb->width && drm_rect_height(&r_logo) < sb->height) {
+		draw_txt_rectangle(sb, font, logo, logo_lines, false, &r_logo, fg_color, bg_color);
+	}
+	draw_txt_rectangle(sb, font, panic_msg, msg_lines, true, &r_msg, fg_color, bg_color);
+}
+
+/*
+ * drm_panic_is_format_supported()
+ * @format: a fourcc color code
+ * Returns: true if supported, false otherwise.
+ *
+ * Check if drm_panic will be able to use this color format.
+ */
+static bool drm_panic_is_format_supported(const struct drm_format_info *format)
+{
+	if (format->num_planes != 1)
+		return false;
+	return format->format == DRM_FORMAT_XRGB8888;
+}
+
+static void draw_panic_plane(struct drm_plane *plane)
+{
+	struct drm_scanout_buffer sb;
+	int ret;
+	unsigned long flags;
+
+	if (!drm_panic_trylock(plane->dev, flags))
+		return;
+
+	ret = plane->helper_private->get_scanout_buffer(plane, &sb);
+
+	if (!ret && drm_panic_is_format_supported(sb.format)) {
+		draw_panic_static(&sb);
+		if (plane->helper_private->panic_flush)
+			plane->helper_private->panic_flush(plane);
+	}
+	drm_panic_unlock(plane->dev, flags);
+}
+
+static struct drm_plane *to_drm_plane(struct kmsg_dumper *kd)
+{
+	return container_of(kd, struct drm_plane, kmsg_panic);
+}
+
+static void drm_panic(struct kmsg_dumper *dumper, enum kmsg_dump_reason reason)
+{
+	struct drm_plane *plane = to_drm_plane(dumper);
+
+	if (reason == KMSG_DUMP_PANIC)
+		draw_panic_plane(plane);
+}
+
+/**
+ * drm_panic_register() - Initialize DRM panic for a device
+ * @dev: the drm device on which the panic screen will be displayed.
+ */
+void drm_panic_register(struct drm_device *dev)
+{
+	struct drm_plane *plane;
+	int registered_plane = 0;
+
+	if (!dev->mode_config.num_total_plane)
+		return;
+
+	drm_for_each_plane(plane, dev) {
+		if (!plane->helper_private || !plane->helper_private->get_scanout_buffer)
+			continue;
+		plane->kmsg_panic.dump = drm_panic;
+		plane->kmsg_panic.max_reason = KMSG_DUMP_PANIC;
+		if (kmsg_dump_register(&plane->kmsg_panic))
+			drm_warn(dev, "Failed to register panic handler\n");
+		else
+			registered_plane++;
+	}
+	if (registered_plane)
+		drm_info(dev, "Registered %d planes with drm panic\n", registered_plane);
+}
+EXPORT_SYMBOL(drm_panic_register);
+
+/**
+ * drm_panic_unregister()
+ * @dev: the drm device previously registered.
+ */
+void drm_panic_unregister(struct drm_device *dev)
+{
+	struct drm_plane *plane;
+
+	if (!dev->mode_config.num_total_plane)
+		return;
+
+	drm_for_each_plane(plane, dev) {
+		if (!plane->helper_private || !plane->helper_private->get_scanout_buffer)
+			continue;
+		kmsg_dump_unregister(&plane->kmsg_panic);
+	}
+}
+EXPORT_SYMBOL(drm_panic_unregister);