This introduces a new drm panic handler, which displays a message when a panic occurs. So when fbcon is disabled, you can still see a kernel panic. This is one of the missing feature, when disabling VT/fbcon in the kernel: https://www.reddit.com/r/linux/comments/10eccv9/config_vtn_in_2023/ Fbcon can be replaced by a userspace kms console, but the panic screen must be done in the kernel. This is a proof of concept, and works with simpledrm, mgag200, ast, and imx. To test it, make sure you're using one of the supported driver, and trigger a panic: echo c > /proc/sysrq-trigger or you can enable CONFIG_DRM_PANIC_DEBUG and echo 1 > /sys/kernel/debug/dri/0/drm_panic_plane_0 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: * Fully support all simpledrm formats using drm conversion helpers * Rename dpanic_* to drm_panic_*, and have more coherent function name. (Thomas Zimmermann) * 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 driver to drm_panic, if the function get_scanout_buffer() exists. (Thomas Zimmermann) * Add mgag200 support. v5: * Change the drawing API, use drm_fb_blit_from_r1() to draw the font. (Thomas Zimmermann) * 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(). * Add ast support. * Add experimental imx/ipuv3 support, to test on an ARM hw. (Maxime Ripard) v6: * Fix sparse and __le32 warnings * Drop the IMX/IPUV3 experiment, it was just to show that it works also on ARM devices. v7: * Add a check to see if the 4cc format is supported by drm_panic. * Add a drm/plane helper to loop over all visible primary buffer, simplifying the get_scanout_buffer implementations * Add a generic implementation for drivers that uses drm_fb_dma. (Maxime Ripard) * Add back the IMX/IPUV3 support, and use the generic implementation. (Maxime Ripard) v8: * Directly register each plane to the panic notifier (Sima) * Replace get_scanout_buffer() with set_scanout_buffer() to simplify the locking. (Thomas Zimmermann) * Add a debugfs entry, to trigger the drm_panic without a real panic (Sima) * Fix the drm_panic Documentation, and include it in drm-kms.rst 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) * Create a debugfs file for each plane in the device's debugfs directory. This allows to test for each plane of each GPU independently. 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). * Use spinlock_irqsave/restore (John Ogness) Daniel Vetter (1): drm/panic: Add drm panic locking Jocelyn Falempe (8): drm/panic: Add a drm panic handler drm/panic: Add support for color format conversion drm/panic: Add debugfs entry to test without triggering panic. drm/fb_dma: Add generic get_scanout_buffer() for drm_panic drm/simpledrm: Add drm_panic support drm/mgag200: Add drm_panic support drm/imx: Add drm_panic support drm/ast: Add drm_panic support Documentation/gpu/drm-kms.rst | 12 + drivers/gpu/drm/Kconfig | 32 ++ drivers/gpu/drm/Makefile | 1 + drivers/gpu/drm/ast/ast_mode.c | 18 + drivers/gpu/drm/drm_atomic_helper.c | 4 + drivers/gpu/drm/drm_drv.c | 5 + drivers/gpu/drm/drm_fb_dma_helper.c | 47 ++ drivers/gpu/drm/drm_panic.c | 581 +++++++++++++++++++++++ drivers/gpu/drm/drm_plane.c | 1 + drivers/gpu/drm/imx/ipuv3/ipuv3-plane.c | 11 +- drivers/gpu/drm/mgag200/mgag200_drv.h | 7 +- drivers/gpu/drm/mgag200/mgag200_mode.c | 18 + drivers/gpu/drm/tiny/simpledrm.c | 16 + include/drm/drm_fb_dma_helper.h | 4 + include/drm/drm_mode_config.h | 10 + include/drm/drm_modeset_helper_vtables.h | 37 ++ include/drm/drm_panic.h | 159 +++++++ include/drm/drm_plane.h | 6 + 18 files changed, 967 insertions(+), 2 deletions(-) create mode 100644 drivers/gpu/drm/drm_panic.c create mode 100644 include/drm/drm_panic.h base-commit: 751b58418250a56329d35de29329f547c43e7c7f -- 2.44.0
