[PATCH v12 0/9] drm/panic: Add a drm panic handler

Mon Apr 15 15:00:31 UTC 2024

On 10/04/2024 10:12, Daniel Vetter wrote:
> On Tue, Apr 09, 2024 at 06:30:39PM +0200, Jocelyn Falempe wrote:
>> drm/panic: Add a drm panic handler
>>
>> 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.
>>
>> It 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
>>
>> Even if this is not yet useful, it will allows to work on more driver support, and better debug information to be added.
>>
>> 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)
>>
>> v11:
>>   * Use macro instead of inline functions for drm_panic_lock/unlock (John Ogness)
>>
>> v12:
>>   * Use array for map and pitch in struct drm_scanout_buffer
>>     to support multi-planar format later. (Thomas Zimmermann)
>>   * Rename drm_panic_gem_get_scanout_buffer to drm_fb_dma_get_scanout_buffer
>>     and build it unconditionally (Thomas Zimmermann)
>>   * Better indent struct drm_scanout_buffer declaration. (Thomas Zimmermann)
> 
> On the series: Acked-by: Daniel Vetter <daniel.vetter at ffwll.ch>
> 
> And apologies for the detours this patch set took and my part in the (too
> many) revisions. I think we should land this and do anything more once
> it's merged and we extend the panic support to more drivers.

Thanks for your help, I just pushed it to drm-misc-next.

Best regards,

-- 

Jocelyn
> 
> Thanks a lot to you for seeing this through!
> 
> Cheers, Sima
>>
>>
>> Best regards,
>>
>>
>> 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      |  42 ++
>>   drivers/gpu/drm/drm_panic.c              | 583 +++++++++++++++++++++++
>>   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                  | 157 ++++++
>>   include/drm/drm_plane.h                  |   6 +
>>   17 files changed, 961 insertions(+), 2 deletions(-)
>>   create mode 100644 drivers/gpu/drm/drm_panic.c
>>   create mode 100644 include/drm/drm_panic.h
>>
>>
>> base-commit: 935a92a1c400285545198ca2800a4c6c519c650a
>> -- 
>> 2.44.0
>>
> 