drm/panic: Add a drm panic handler

This module displays a user friendly message when a kernel panic
occurs. It currently doesn't contain any debug information,
but that can be added later.

v2
 * Use get_scanout_buffer() instead of the drm client API.
  (Thomas Zimmermann)
 * Add the panic reason to the panic message (Nerdopolis)
 * Add an exclamation mark (Nerdopolis)

v3
 * Rework the drawing functions, to write the pixels line by line and
 to use the drm conversion helper to support other formats.
 (Thomas Zimmermann)

v4
 * Use drm_fb_r1_to_32bit for fonts (Thomas Zimmermann)
 * Remove the default y to DRM_PANIC config option (Thomas Zimmermann)
 * Add foreground/background color config option
 * Fix the bottom lines not painted if the framebuffer height
   is not a multiple of the font height.
 * Automatically register the device to drm_panic, if the function
   get_scanout_buffer exists. (Thomas Zimmermann)

v5
 * Change the drawing API, use drm_fb_blit_from_r1() to draw the font.
 * Also add drm_fb_fill() to fill area with background color.
 * Add draw_pixel_xy() API for drivers that can't provide a linear buffer.
 * Add a flush() callback for drivers that needs to synchronize the buffer.
 * Add a void *private field, so drivers can pass private data to
   draw_pixel_xy() and flush().

v6
 * Fix sparse warning for panic_msg and logo.

v7
 * Add select DRM_KMS_HELPER for the color conversion functions.

v8
 * Register directly each plane to the panic notifier (Sima)
 * Add raw_spinlock to properly handle concurrency (Sima)
 * Register plane instead of device, to avoid looping through plane
   list, and simplify code.
 * Replace get_scanout_buffer() logic with drm_panic_set_buffer()
  (Thomas Zimmermann)
 * Removed the draw_pixel_xy() API, will see later if it can be added back.

v9
 * Revert to using get_scanout_buffer() (Sima)
 * Move get_scanout_buffer() and panic_flush() to the plane helper
   functions (Thomas Zimmermann)
 * Register all planes with get_scanout_buffer() to the panic notifier
 * Use drm_panic_lock() to protect against race (Sima)

v10
 * Move blit and fill functions back in drm_panic (Thomas Zimmermann).
 * Simplify the text drawing functions.
 * Use kmsg_dumper instead of panic_notifier (Sima).

v12
 * Use array for map and pitch in struct drm_scanout_buffer
   to support multi-planar format later. (Thomas Zimmermann)
 * Better indent struct drm_scanout_buffer declaration. (Thomas Zimmermann)

Signed-off-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240409163432.352518-3-jfalempe@redhat.com
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 4 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index c157500b3135..535b624d4c9d 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -43,6 +43,7 @@
 #include <drm/drm_file.h>
 #include <drm/drm_managed.h>
 #include <drm/drm_mode_object.h>
+#include <drm/drm_panic.h>
 #include <drm/drm_print.h>
 #include <drm/drm_privacy_screen_machine.h>
 
@@ -944,6 +945,7 @@ int drm_dev_register(struct drm_device *dev, unsigned long flags)
 		if (ret)
 			goto err_unload;
 	}
+	drm_panic_register(dev);
 
 	DRM_INFO("Initialized %s %d.%d.%d %s for %s on minor %d\n",
 		 driver->name, driver->major, driver->minor,
@@ -988,6 +990,8 @@ void drm_dev_unregister(struct drm_device *dev)
 {
 	dev->registered = false;
 
+	drm_panic_unregister(dev);
+
 	drm_client_dev_unregister(dev);
 
 	if (drm_core_check_feature(dev, DRIVER_MODESET))